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    <title>Tigris · 仁才德</title>
    <link>https://jared.lynskey.co.nz/zh-cn/tags/tigris/</link>
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    <item>
      <title>直传 S3 也不放弃图片压缩：Tigris 对象通知与 Django</title>
      <link>https://jared.lynskey.co.nz/zh-cn/posts/2026/tigris-object-notifications/</link>
      <guid isPermaLink="true">https://jared.lynskey.co.nz/zh-cn/posts/2026/tigris-object-notifications/</guid>
      <pubDate>Sat, 07 Nov 2026 00:00:00 +1300</pubDate>
      <dc:creator>Jared Lynskey</dc:creator>
      <category>Tigris</category>
      <category>S3</category>
      <category>S3 Event Notifications</category>
      <category>Presigned URLs</category>
      <category>Image Uploads</category>
      <category>Image Compression</category>
      <category>Object Storage</category>
      <category>Webhooks</category>
      <category>Django</category>
      <category>Fly.io</category>
      <category>Discord</category>
      <description>用预签名 URL 直传 S3 很快，但后端根本不知道文件什么时候到了，图片压缩和缩略图就变得别扭。Tigris 对象通知解决了这个问题：bucket 向 Django 的 webhook 发一个 POST，用户还在打字，照片就已经处理好了。同一个信号还能把日志文件变成 Discord 告警。</description>
      <content:encoded><![CDATA[<p>我做过的每一个图片上传功能，骨子里都有同一个矛盾。上传的人希望照片赶紧传上去。我希望服务器把图片压缩好、生成缩略图、算出 blurhash 和几个主色、去掉不该留在里面的元数据，再按应用其他部分期望的方式存起来。要把我这份清单做全，最省事的办法是让文件经过 API，而上传的人那份清单，恰恰就是被这一步拖慢的。</p>
<p>快的办法是预签名 URL。API 签出一个 URL，客户端把文件直接 PUT 进 bucket，字节完全不经过 API。它能成为标准答案是有道理的。可你一这么做，后端就被踢出了整个流程：它发出一个 URL，然后就什么都听不到了。文件到了吗？大小是预期的吗？它到底是不是 JPEG？总得有什么东西告诉后端，而常见的几个选项都有点让人叹气：相信客户端会回调一声&quot;传好了&quot;（客户端会撒谎、会崩溃、会断网），按计划轮询 bucket（又慢又浪费），或者等第一次读取时再懒处理（第一个看的人买单，而且你依然不知道文件什么时候才能放心引用）。这就是为什么直接上传到 S3 看起来比实际更难。上传本身很容易，缺的是信号。</p>
<p>对象通知就是这个信号。我在 Fly.io 上用的 S3 兼容存储 Tigris，每当 bucket 里有对象被创建或删除，都会向你的应用 POST 一小段 JSON。在 AWS 上对应的东西叫 S3 事件通知，但通常要先接上 Lambda、SQS 队列或者 EventBridge，事件才能到你的代码（SNS 倒是能直接向 HTTPS 端点 POST，可那样你得先确认订阅、再验证签名）。Tigris 把它压缩成一个发往你自己 URL 的 HTTP 请求，存储到后端的信号传递，大概没法比这更简单了。这个功能存在的意义，就是让 bucket 能直接跟你的后端说话，不用你在中间搭桥。</p>
<p>这篇文章讲完整个流程：怎么配置，接收事件的 Django 端点，服务端处理一步不少的预签名上传，以及几个坑（CORS、大小限制、过期、多文件）。最后再看同一个信号怎么干后台的活：日志文件一落进 bucket 就变成 Discord 告警，让我删掉了一个伺候了好几个月的 cron 任务。</p>

<h2 class="relative group">简短的答案
    <div id="简短的答案" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%ae%80%e7%9f%ad%e7%9a%84%e7%ad%94%e6%a1%88" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>在 Tigris 控制台里打开 bucket，进 Settings，再进 Object notifications。填一个你应用上的 HTTPS URL，认证选 basic auth（一组用户名和密码，Tigris 会放在 <code>Authorization</code> 头里发过来；另一个选项是 bearer token）。再加一个过滤条件，只接收你关心的那些 key。过滤条件是一个类 SQL 的表达式，&ldquo;只要这篇文章处理的那三个前缀&quot;写出来是这样：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-sql" data-lang="sql"><span class="line"><span class="cl"><span class="k">WHERE</span><span class="w"> </span><span class="o">`</span><span class="k">key</span><span class="o">`</span><span class="w"> </span><span class="n">REGEXP</span><span class="w"> </span><span class="s2">&#34;^(uploads/raw|logs/api|media)/&#34;</span></span></span></code></pre></div></div>
<p><figure><span class="mc-img"><img
    class="my-0 rounded-md"
    loading="lazy"
    decoding="async"
    fetchpriority="auto"
    alt="Tigris bucket 设置的 Notifications 标签页：对象通知已打开，一个 webhook URL，用户名加密码的 basic auth，以及一个类 SQL 的 key 过滤条件"
    width="1204"
    height="671"
    src="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-object-notifications-settings_hu_7e9da7c6ca1125db.webp"
    srcset="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-object-notifications-settings_hu_7e9da7c6ca1125db.webp 800w, https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-object-notifications-settings_hu_4ddc968851d1f052.webp 1280w"
    sizes="(min-width: 768px) 50vw, 65vw"
    data-zoom-src="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-object-notifications-settings_hu_4ddc968851d1f052.webp"></span><figcaption>整套配置就这些：你应用上的一个 HTTPS URL、basic auth，以及对 key 的过滤条件。这里的 bucket 名和 URL 已换成示例。</figcaption></figure>
</p>
<p>之后每有变化，Tigris 就会发来这样一批事件：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="nt">&#34;events&#34;</span><span class="p">:</span> <span class="p">[</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span>
</span></span><span class="line"><span class="cl">      <span class="nt">&#34;eventName&#34;</span><span class="p">:</span> <span class="s2">&#34;OBJECT_CREATED_PUT&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">      <span class="nt">&#34;eventTime&#34;</span><span class="p">:</span> <span class="s2">&#34;2026-11-07T09:12:44Z&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">      <span class="nt">&#34;bucket&#34;</span><span class="p">:</span> <span class="s2">&#34;example-bucket&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">      <span class="nt">&#34;object&#34;</span><span class="p">:</span> <span class="p">{</span> <span class="nt">&#34;key&#34;</span><span class="p">:</span> <span class="s2">&#34;uploads/raw/1f3c.jpg&#34;</span><span class="p">,</span> <span class="nt">&#34;size&#34;</span><span class="p">:</span> <span class="mi">48213</span><span class="p">,</span> <span class="nt">&#34;eTag&#34;</span><span class="p">:</span> <span class="s2">&#34;9b2c…&#34;</span> <span class="p">}</span>
</span></span><span class="line"><span class="cl">    <span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="p">]</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre></div></div>
<p>你会遇到的事件名有 <code>OBJECT_CREATED_PUT</code>、<code>OBJECT_CREATED_MULTIPART</code>、<code>OBJECT_CREATED_COPY</code> 和 <code>OBJECT_DELETED</code>，另外还有重命名和存储层级变更。你的端点负责校验 auth，按 key 前缀把每个事件分发出去，然后在十秒内返回 2xx。有三件事最好一开始就考虑进去：投递是 at least once 的，所以你会收到重复；事件是成批发送的，所以一个请求里可能带着好几个；它们还可能乱序到达，所以别拿到达顺序去判断哪个是&quot;最新&rdquo;。</p>

<h2 class="relative group">接收 bucket 事件的 Django webhook
    <div id="接收-bucket-事件的-django-webhook" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%8e%a5%e6%94%b6-bucket-%e4%ba%8b%e4%bb%b6%e7%9a%84-django-webhook" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>这个 view 是故意写得很无聊的。它校验 auth、解析请求体，然后把每个事件交给路由：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">base64</span><span class="o">,</span> <span class="nn">hmac</span><span class="o">,</span> <span class="nn">json</span><span class="o">,</span> <span class="nn">logging</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.conf</span> <span class="kn">import</span> <span class="n">settings</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.http</span> <span class="kn">import</span> <span class="n">JsonResponse</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.views.decorators.csrf</span> <span class="kn">import</span> <span class="n">csrf_exempt</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.views.decorators.http</span> <span class="kn">import</span> <span class="n">require_POST</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">.bucket_events</span> <span class="kn">import</span> <span class="n">handle</span><span class="p">,</span> <span class="n">parse</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="n">logger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="vm">__name__</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">_authorised</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="n">secret</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">bool</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="n">header</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">headers</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;Authorization&#34;</span><span class="p">,</span> <span class="s2">&#34;&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="ow">not</span> <span class="n">header</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s2">&#34;Basic &#34;</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="kc">False</span>
</span></span><span class="line"><span class="cl">    <span class="k">try</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="n">user</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">password</span> <span class="o">=</span> <span class="n">base64</span><span class="o">.</span><span class="n">b64decode</span><span class="p">(</span><span class="n">header</span><span class="p">[</span><span class="mi">6</span><span class="p">:])</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span><span class="o">.</span><span class="n">partition</span><span class="p">(</span><span class="s2">&#34;:&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">except</span> <span class="p">(</span><span class="ne">ValueError</span><span class="p">,</span> <span class="ne">UnicodeDecodeError</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="kc">False</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">hmac</span><span class="o">.</span><span class="n">compare_digest</span><span class="p">(</span><span class="n">user</span><span class="o">.</span><span class="n">encode</span><span class="p">(),</span> <span class="sa">b</span><span class="s2">&#34;tigris&#34;</span><span class="p">)</span> <span class="ow">and</span> <span class="n">hmac</span><span class="o">.</span><span class="n">compare_digest</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="n">password</span><span class="o">.</span><span class="n">encode</span><span class="p">(),</span> <span class="n">secret</span><span class="o">.</span><span class="n">encode</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="nd">@csrf_exempt</span>
</span></span><span class="line"><span class="cl"><span class="nd">@require_POST</span>
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">bucket_webhook</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="n">secret</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">BUCKET_WEBHOOK_SECRET</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="ow">not</span> <span class="n">secret</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">JsonResponse</span><span class="p">({</span><span class="s2">&#34;error&#34;</span><span class="p">:</span> <span class="s2">&#34;not configured&#34;</span><span class="p">},</span> <span class="n">status</span><span class="o">=</span><span class="mi">503</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="ow">not</span> <span class="n">_authorised</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="n">secret</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">JsonResponse</span><span class="p">({</span><span class="s2">&#34;error&#34;</span><span class="p">:</span> <span class="s2">&#34;unauthorised&#34;</span><span class="p">},</span> <span class="n">status</span><span class="o">=</span><span class="mi">401</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">try</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="n">body</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">request</span><span class="o">.</span><span class="n">body</span> <span class="ow">or</span> <span class="sa">b</span><span class="s2">&#34;</span><span class="si">{}</span><span class="s2">&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">except</span> <span class="ne">ValueError</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">JsonResponse</span><span class="p">({</span><span class="s2">&#34;error&#34;</span><span class="p">:</span> <span class="s2">&#34;invalid json&#34;</span><span class="p">},</span> <span class="n">status</span><span class="o">=</span><span class="mi">400</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="n">event</span> <span class="ow">in</span> <span class="n">parse</span><span class="p">(</span><span class="n">body</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="k">try</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">            <span class="n">handle</span><span class="p">(</span><span class="n">event</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">        <span class="k">except</span> <span class="ne">Exception</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">            <span class="n">logger</span><span class="o">.</span><span class="n">exception</span><span class="p">(</span><span class="s2">&#34;bucket event failed: </span><span class="si">%s</span><span class="s2">&#34;</span><span class="p">,</span> <span class="n">event</span><span class="o">.</span><span class="n">key</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">JsonResponse</span><span class="p">({</span><span class="s2">&#34;ok&#34;</span><span class="p">:</span> <span class="kc">True</span><span class="p">})</span></span></span></code></pre></div></div>
<p><code>compare_digest</code> 的作用，是让校验不管收到什么都花同样的时间（要传 bytes，因为传字符串时它遇到非 ASCII 输入会直接抛异常，一个精心构造的头拿到的就是 500 而不是 401）。如果 secret 没有配置，比如在一台刚开出来的 staging 机器上，端点会拒绝所有请求，而不是放行所有请求。handler 抛了异常，会记一条日志，但照样回 200：Tigris 对一切非 2xx 的响应都会重试，重试撞上的还是同一个 bug，而且到那时事件已经被认领了（往下两节会讲），重试其实什么也干不了。真正让问题得到修复的，是那条日志。这里有个前提：失败得是确定性的。存储那边一次短暂的超时，会把这个事件永远消耗掉：照片无所谓，因为保存时可以自己处理；但日志文件的告警就丢了。如果你在意这一点，就在 <code>except</code> 里释放认领，然后回 500 让 Tigris 重试，并接受真正的 bug 会一直重试到修好为止。</p>

<h2 class="relative group">按前缀路由
    <div id="按前缀路由" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%8c%89%e5%89%8d%e7%bc%80%e8%b7%af%e7%94%b1" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>bucket 里的东西本来就是按前缀组织的，所以按前缀路由最顺手。每种用途就是一个函数，加上表里的一行：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">HANDLERS</span> <span class="o">=</span> <span class="p">[</span>
</span></span><span class="line"><span class="cl">    <span class="p">(</span><span class="s2">&#34;uploads/raw/&#34;</span><span class="p">,</span>   <span class="n">on_raw_photo</span><span class="p">),</span>
</span></span><span class="line"><span class="cl">    <span class="p">(</span><span class="s2">&#34;logs/api/&#34;</span><span class="p">,</span>      <span class="n">on_api_log_file</span><span class="p">),</span>
</span></span><span class="line"><span class="cl">    <span class="p">(</span><span class="s2">&#34;media/&#34;</span><span class="p">,</span>         <span class="n">on_media_change</span><span class="p">),</span>
</span></span><span class="line"><span class="cl"><span class="p">]</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">handle</span><span class="p">(</span><span class="n">event</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="n">prefix</span><span class="p">,</span> <span class="n">fn</span> <span class="ow">in</span> <span class="n">HANDLERS</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="n">event</span><span class="o">.</span><span class="n">key</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="n">prefix</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">            <span class="k">if</span> <span class="n">claim</span><span class="p">(</span><span class="n">event</span><span class="p">):</span>  <span class="c1"># 见下文</span>
</span></span><span class="line"><span class="cl">                <span class="n">fn</span><span class="p">(</span><span class="n">event</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">            <span class="k">return</span></span></span></code></pre></div></div>
<p>以后要加第四种用途，就是多一个函数、多一行。我比自己预想的还要喜欢这种写法。</p>

<h2 class="relative group">At least once 的意思是&quot;可能两次&quot;
    <div id="at-least-once-的意思是可能两次" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#at-least-once-%e7%9a%84%e6%84%8f%e6%80%9d%e6%98%af%e5%8f%af%e8%83%bd%e4%b8%a4%e6%ac%a1" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>端点响应慢或者返回错误时，Tigris 会重试，而且和大多数 webhook 发送方一样，它不保证每个事件你只会看到一次。所以在 handler 运行之前，先按 <code>(key, eTag, eventName)</code> 认领这个事件。eTag 很关键：文件被覆盖后就是一个新版本，eTag 也是新的，理应再处理一次；同一个版本的重复投递则不该再处理。</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.core.cache</span> <span class="kn">import</span> <span class="n">cache</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">claim</span><span class="p">(</span><span class="n">event</span><span class="p">,</span> <span class="n">ttl</span><span class="o">=</span><span class="mi">7</span> <span class="o">*</span> <span class="mi">24</span> <span class="o">*</span> <span class="mi">3600</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">bool</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="n">k</span> <span class="o">=</span> <span class="sa">f</span><span class="s2">&#34;bucket-event:</span><span class="si">{</span><span class="n">event</span><span class="o">.</span><span class="n">name</span><span class="si">}</span><span class="s2">:</span><span class="si">{</span><span class="n">event</span><span class="o">.</span><span class="n">key</span><span class="si">}</span><span class="s2">:</span><span class="si">{</span><span class="n">event</span><span class="o">.</span><span class="n">etag</span><span class="si">}</span><span class="s2">&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">cache</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">k</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">ttl</span><span class="p">)</span>  <span class="c1"># 已经被别人认领就返回 False</span></span></span></code></pre></div></div>
<p><code>cache.add</code> 只在 key 不存在时才写入，这在 Redis 里是原子操作，所以两台机器收到同一次重试，不可能都抢到。实际项目里我用的是基于数据库的租约，因为我希望它在 Redis 被清空后还能留着，但思路完全一样。</p>

<h2 class="relative group">图片直传 S3，处理流程一样不少
    <div id="图片直传-s3处理流程一样不少" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%9b%be%e7%89%87%e7%9b%b4%e4%bc%a0-s3%e5%a4%84%e7%90%86%e6%b5%81%e7%a8%8b%e4%b8%80%e6%a0%b7%e4%b8%8d%e5%b0%91" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>前面那些管道活，值就值在这一部分。</p>
<p>以前，给一条帖子选照片时，应用会先把照片攥在手里，等你点了&quot;发布&quot;，再把它们全部以 base64 发给 API。API 接着缩放尺寸、生成缩略图、算出主色和 blurhash，全部做完才回复。十张照片再碰上慢网速，那个转圈就转得很久。而且一个带着十张 base64 照片的请求，对 API 服务器来说是一个又大又慢、还得整个攥在内存里的请求体，这也是我一直悄悄把照片压得很小的真正原因。</p>
<p>现在变成了四步，而且每一步后端都知道。</p>

<h3 class="relative group">1. 客户端先缩图，再申请一个槽位
    <div id="1-客户端先缩图再申请一个槽位" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#1-%e5%ae%a2%e6%88%b7%e7%ab%af%e5%85%88%e7%bc%a9%e5%9b%be%e5%86%8d%e7%94%b3%e8%af%b7%e4%b8%80%e4%b8%aa%e6%a7%bd%e4%bd%8d" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>应用仍然会在设备上缩图，缩到服务器保留的最长边（1080px），存成质量 0.7 的 JPEG。这一步缩放只是为了省用户的流量，没有别的目的。然后它向 API 申请一个上传槽位：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">uuid</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">timedelta</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">boto3</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.utils</span> <span class="kn">import</span> <span class="n">timezone</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="n">s3</span> <span class="o">=</span> <span class="n">boto3</span><span class="o">.</span><span class="n">client</span><span class="p">(</span><span class="s2">&#34;s3&#34;</span><span class="p">,</span> <span class="n">endpoint_url</span><span class="o">=</span><span class="s2">&#34;https://fly.storage.tigris.dev&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">BUCKET</span> <span class="o">=</span> <span class="s2">&#34;example-bucket&#34;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">create_upload_slot</span><span class="p">(</span><span class="n">user</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="n">public_id</span> <span class="o">=</span> <span class="n">uuid</span><span class="o">.</span><span class="n">uuid4</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="n">key</span> <span class="o">=</span> <span class="sa">f</span><span class="s2">&#34;uploads/raw/</span><span class="si">{</span><span class="n">public_id</span><span class="si">}</span><span class="s2">.jpg&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="n">upload</span> <span class="o">=</span> <span class="n">PhotoUpload</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">create</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="n">user</span><span class="o">=</span><span class="n">user</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">public_id</span><span class="o">=</span><span class="n">public_id</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">raw_key</span><span class="o">=</span><span class="n">key</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">expires_at</span><span class="o">=</span><span class="n">timezone</span><span class="o">.</span><span class="n">now</span><span class="p">()</span> <span class="o">+</span> <span class="n">timedelta</span><span class="p">(</span><span class="n">days</span><span class="o">=</span><span class="mi">2</span><span class="p">),</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">url</span> <span class="o">=</span> <span class="n">s3</span><span class="o">.</span><span class="n">generate_presigned_url</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;put_object&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">Params</span><span class="o">=</span><span class="p">{</span><span class="s2">&#34;Bucket&#34;</span><span class="p">:</span> <span class="n">BUCKET</span><span class="p">,</span> <span class="s2">&#34;Key&#34;</span><span class="p">:</span> <span class="n">key</span><span class="p">,</span> <span class="s2">&#34;ContentType&#34;</span><span class="p">:</span> <span class="s2">&#34;image/jpeg&#34;</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">        <span class="n">ExpiresIn</span><span class="o">=</span><span class="mi">15</span> <span class="o">*</span> <span class="mi">60</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;upload_id&#34;</span><span class="p">:</span> <span class="nb">str</span><span class="p">(</span><span class="n">upload</span><span class="o">.</span><span class="n">public_id</span><span class="p">),</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;url&#34;</span><span class="p">:</span> <span class="n">url</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;method&#34;</span><span class="p">:</span> <span class="s2">&#34;PUT&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;headers&#34;</span><span class="p">:</span> <span class="p">{</span><span class="s2">&#34;Content-Type&#34;</span><span class="p">:</span> <span class="s2">&#34;image/jpeg&#34;</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;expires_in&#34;</span><span class="p">:</span> <span class="mi">15</span> <span class="o">*</span> <span class="mi">60</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="p">}</span></span></span></code></pre></div></div>
<p>槽位先是数据库里的一行，然后才是一个文件。正因为这样，服务器才知道是谁申请的、什么时候过期，以及后来它到底有没有被用过。</p>

<h3 class="relative group">2. 客户端直接 PUT 到 bucket
    <div id="2-客户端直接-put-到-bucket" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#2-%e5%ae%a2%e6%88%b7%e7%ab%af%e7%9b%b4%e6%8e%a5-put-%e5%88%b0-bucket" aria-label="锚点">#</a>
    </span>
    
</h3>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-ts" data-lang="ts"><span class="line"><span class="cl"><span class="kr">const</span> <span class="nx">slot</span> <span class="o">=</span> <span class="k">await</span> <span class="nx">api</span><span class="p">.</span><span class="nx">post</span><span class="p">(</span><span class="s2">&#34;/photo-uploads/&#34;</span><span class="p">);</span>
</span></span><span class="line"><span class="cl"><span class="kr">const</span> <span class="nx">res</span> <span class="o">=</span> <span class="k">await</span> <span class="nx">fetch</span><span class="p">(</span><span class="nx">slot</span><span class="p">.</span><span class="nx">url</span><span class="p">,</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="nx">method</span>: <span class="kt">slot.method</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">  <span class="nx">headers</span>: <span class="kt">slot.headers</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">  <span class="nx">body</span>: <span class="kt">blob</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"><span class="p">});</span>
</span></span><span class="line"><span class="cl"><span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nx">res</span><span class="p">.</span><span class="nx">ok</span><span class="p">)</span> <span class="k">throw</span> <span class="k">new</span> <span class="nb">Error</span><span class="p">(</span><span class="s2">&#34;upload refused&#34;</span><span class="p">);</span>
</span></span><span class="line"><span class="cl"><span class="c1">// 把 slot.upload_id 留着，保存时要用
</span></span></span></code></pre></div></div>
<p>API 从头到尾见不到这些字节。浏览器、React Native 或原生应用都是同一套做法；唯一的区别是浏览器需要在 bucket 上配一条 CORS 规则，这个放在下面的坑里讲。</p>

<h3 class="relative group">3. Tigris 通知后端，处理流程跑起来
    <div id="3-tigris-通知后端处理流程跑起来" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#3-tigris-%e9%80%9a%e7%9f%a5%e5%90%8e%e7%ab%af%e5%a4%84%e7%90%86%e6%b5%81%e7%a8%8b%e8%b7%91%e8%b5%b7%e6%9d%a5" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>几秒之内，Tigris 就会针对 <code>uploads/raw/…</code> 发来一个 <code>OBJECT_CREATED_PUT</code>，handler 跑的是 base64 路径一直在用的那套图片处理流程，而这时用户还在输入标题：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">io</span> <span class="kn">import</span> <span class="n">BytesIO</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">PIL</span> <span class="kn">import</span> <span class="n">Image</span><span class="p">,</span> <span class="n">ImageOps</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.core.files.base</span> <span class="kn">import</span> <span class="n">ContentFile</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.utils</span> <span class="kn">import</span> <span class="n">timezone</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">blurhash</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="n">MAX_BYTES</span> <span class="o">=</span> <span class="mi">15</span> <span class="o">*</span> <span class="mi">1024</span> <span class="o">*</span> <span class="mi">1024</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">on_raw_photo</span><span class="p">(</span><span class="n">event</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="ow">not</span> <span class="n">event</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s2">&#34;OBJECT_CREATED&#34;</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="n">event</span><span class="o">.</span><span class="n">size</span> <span class="o">&gt;</span> <span class="n">MAX_BYTES</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="n">s3</span><span class="o">.</span><span class="n">delete_object</span><span class="p">(</span><span class="n">Bucket</span><span class="o">=</span><span class="n">event</span><span class="o">.</span><span class="n">bucket</span><span class="p">,</span> <span class="n">Key</span><span class="o">=</span><span class="n">event</span><span class="o">.</span><span class="n">key</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span>
</span></span><span class="line"><span class="cl">    <span class="n">upload</span> <span class="o">=</span> <span class="n">PhotoUpload</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">raw_key</span><span class="o">=</span><span class="n">event</span><span class="o">.</span><span class="n">key</span><span class="p">,</span> <span class="n">processed_at</span><span class="o">=</span><span class="kc">None</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="n">upload</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span>
</span></span><span class="line"><span class="cl">    <span class="n">data</span> <span class="o">=</span> <span class="n">s3</span><span class="o">.</span><span class="n">get_object</span><span class="p">(</span><span class="n">Bucket</span><span class="o">=</span><span class="n">event</span><span class="o">.</span><span class="n">bucket</span><span class="p">,</span> <span class="n">Key</span><span class="o">=</span><span class="n">event</span><span class="o">.</span><span class="n">key</span><span class="p">)[</span><span class="s2">&#34;Body&#34;</span><span class="p">]</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="n">process</span><span class="p">(</span><span class="n">upload</span><span class="p">,</span> <span class="n">data</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">to_webp</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="n">longest</span><span class="p">,</span> <span class="n">quality</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="n">im</span> <span class="o">=</span> <span class="n">im</span><span class="o">.</span><span class="n">copy</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="n">im</span><span class="o">.</span><span class="n">thumbnail</span><span class="p">((</span><span class="n">longest</span><span class="p">,</span> <span class="n">longest</span><span class="p">))</span>
</span></span><span class="line"><span class="cl">    <span class="n">buf</span> <span class="o">=</span> <span class="n">BytesIO</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="n">im</span><span class="o">.</span><span class="n">save</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="s2">&#34;WEBP&#34;</span><span class="p">,</span> <span class="n">quality</span><span class="o">=</span><span class="n">quality</span><span class="p">,</span> <span class="n">icc_profile</span><span class="o">=</span><span class="n">im</span><span class="o">.</span><span class="n">info</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;icc_profile&#34;</span><span class="p">))</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">ContentFile</span><span class="p">(</span><span class="n">buf</span><span class="o">.</span><span class="n">getvalue</span><span class="p">())</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">process</span><span class="p">(</span><span class="n">upload</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="k">with</span> <span class="n">Image</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">BytesIO</span><span class="p">(</span><span class="n">data</span><span class="p">))</span> <span class="k">as</span> <span class="n">im</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="n">im</span> <span class="o">=</span> <span class="n">ImageOps</span><span class="o">.</span><span class="n">exif_transpose</span><span class="p">(</span><span class="n">im</span><span class="p">)</span><span class="o">.</span><span class="n">convert</span><span class="p">(</span><span class="s2">&#34;RGB&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">        <span class="n">im</span><span class="o">.</span><span class="n">thumbnail</span><span class="p">((</span><span class="mi">1080</span><span class="p">,</span> <span class="mi">1080</span><span class="p">))</span>
</span></span><span class="line"><span class="cl">        <span class="n">upload</span><span class="o">.</span><span class="n">width</span><span class="p">,</span> <span class="n">upload</span><span class="o">.</span><span class="n">height</span> <span class="o">=</span> <span class="n">im</span><span class="o">.</span><span class="n">size</span>
</span></span><span class="line"><span class="cl">        <span class="n">upload</span><span class="o">.</span><span class="n">dominant_color</span> <span class="o">=</span> <span class="s2">&#34;#</span><span class="si">%02x%02x%02x</span><span class="s2">&#34;</span> <span class="o">%</span> <span class="n">im</span><span class="o">.</span><span class="n">resize</span><span class="p">((</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">))</span><span class="o">.</span><span class="n">getpixel</span><span class="p">((</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">))</span>
</span></span><span class="line"><span class="cl">        <span class="n">upload</span><span class="o">.</span><span class="n">image</span><span class="o">.</span><span class="n">save</span><span class="p">(</span><span class="sa">f</span><span class="s2">&#34;</span><span class="si">{</span><span class="n">upload</span><span class="o">.</span><span class="n">public_id</span><span class="si">}</span><span class="s2">.webp&#34;</span><span class="p">,</span> <span class="n">to_webp</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="mi">1080</span><span class="p">,</span> <span class="mi">80</span><span class="p">),</span> <span class="n">save</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">        <span class="n">upload</span><span class="o">.</span><span class="n">thumbnail</span><span class="o">.</span><span class="n">save</span><span class="p">(</span><span class="sa">f</span><span class="s2">&#34;</span><span class="si">{</span><span class="n">upload</span><span class="o">.</span><span class="n">public_id</span><span class="si">}</span><span class="s2">_t.webp&#34;</span><span class="p">,</span> <span class="n">to_webp</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="mi">320</span><span class="p">,</span> <span class="mi">70</span><span class="p">),</span> <span class="n">save</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">        <span class="n">upload</span><span class="o">.</span><span class="n">blurhash</span> <span class="o">=</span> <span class="n">blurhash</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="n">im</span><span class="o">.</span><span class="n">resize</span><span class="p">((</span><span class="mi">32</span><span class="p">,</span> <span class="mi">32</span><span class="p">)),</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">upload</span><span class="o">.</span><span class="n">processed_at</span> <span class="o">=</span> <span class="n">timezone</span><span class="o">.</span><span class="n">now</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="n">upload</span><span class="o">.</span><span class="n">save</span><span class="p">()</span></span></span></code></pre></div></div>
<p><code>on_raw_photo</code> 的第一行比看上去重要。路由会把 <code>uploads/raw/</code> 下的每一个事件都送到这里，包括孤儿清理和上面那个大小检查自己触发的删除，而对一个已经不在的 key 调 <code>get_object</code>，只会抛异常。</p>
<p>所以客户端那一步缩放，从头到尾只是为了传输。格式（WebP）、尺寸、缩略图、占位图，以及存下来的宽高，依然由服务器说了算。经 Pillow 重新编码还会顺手丢掉 EXIF 块，手机相机就是把 GPS 位置放在那里的，所以隐私清理是白送的。ICC 配置文件本来也会一起丢掉，那会让广色域的手机照片颜色稍微偏一点，所以 <code>to_webp</code> 把它原样带了过去。如果你更想保留像素级的原图，那就别在客户端缩；流程完全一样，只是 PUT 更大，而更大的 PUT 恰恰是这套设计让它变便宜的那件事。有一个坑：iPhone 的原图是 HEIC，Pillow 只有装了 <code>pillow-heif</code> 才打得开。</p>

<h3 class="relative group">4. 保存时挂上照片，从不等 webhook
    <div id="4-保存时挂上照片从不等-webhook" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#4-%e4%bf%9d%e5%ad%98%e6%97%b6%e6%8c%82%e4%b8%8a%e7%85%a7%e7%89%87%e4%bb%8e%e4%b8%8d%e7%ad%89-webhook" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>用户点&quot;发布&quot;时，请求里带的是 <code>upload_ids</code>，而不是图片数据。服务器逐个查找，有三种结果：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">take</span><span class="p">(</span><span class="n">user</span><span class="p">,</span> <span class="n">upload_ids</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="n">uploads</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">PhotoUpload</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="n">user</span><span class="o">=</span><span class="n">user</span><span class="p">,</span> <span class="n">public_id__in</span><span class="o">=</span><span class="n">upload_ids</span><span class="p">,</span> <span class="n">expires_at__gt</span><span class="o">=</span><span class="n">timezone</span><span class="o">.</span><span class="n">now</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="p">))</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">uploads</span><span class="p">)</span> <span class="o">!=</span> <span class="nb">len</span><span class="p">(</span><span class="nb">set</span><span class="p">(</span><span class="n">upload_ids</span><span class="p">)):</span>     <span class="c1"># 已过期，或不属于这个用户</span>
</span></span><span class="line"><span class="cl">        <span class="k">raise</span> <span class="n">UploadNotReadyError</span><span class="p">(</span><span class="n">upload_ids</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="n">upload</span> <span class="ow">in</span> <span class="n">uploads</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="n">upload</span><span class="o">.</span><span class="n">processed_at</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>          <span class="c1"># webhook 还没到</span>
</span></span><span class="line"><span class="cl">            <span class="n">data</span> <span class="o">=</span> <span class="n">read_raw</span><span class="p">(</span><span class="n">upload</span><span class="p">)</span>              <span class="c1"># PUT 没落地就是 None</span>
</span></span><span class="line"><span class="cl">            <span class="k">if</span> <span class="n">data</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">raise</span> <span class="n">UploadNotReadyError</span><span class="p">(</span><span class="n">upload</span><span class="o">.</span><span class="n">public_id</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">            <span class="n">process</span><span class="p">(</span><span class="n">upload</span><span class="p">,</span> <span class="n">data</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">uploads</span></span></span></code></pre></div></div>
<p>如果通知已经跑过了，处理好的文件就原样挂上去。如果文件在 bucket 里，通知却还没到，保存就当场把它处理掉，所以发帖从来不用等 webhook。通知是抢跑，不是依赖。如果文件根本不在，或者某个 id 已经过期、属于别人，保存会返回一个校验错误，应用稍等一下再重试；应用在发送前会先等自己的 PUT 完成，所以实际上这种情况很少见。</p>
<p>让这套东西站得住的几个细节。槽位属于某个用户，所以服务器只接受同一个人创建的上传 id，不然任何看到 id 的人都能把你的照片挂到他自己的帖子上。处处都有退路：申请槽位失败、PUT 被拒，或者 API 是旧版本，应用就照老办法发 base64。只有当每张新照片都有槽位时它才走上传这条路，所以一条帖子的图片要么全是上传、要么全是 base64，顺序始终是同一份列表。孤儿会过期：有些人选了照片又放弃了，所以一直没被挂上的上传两天后过期，现有的孤立媒体清理任务会把它的文件清掉。</p>

<h2 class="relative group">预签名 URL 上传的坑：CORS、大小限制、过期、多文件
    <div id="预签名-url-上传的坑cors大小限制过期多文件" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e9%a2%84%e7%ad%be%e5%90%8d-url-%e4%b8%8a%e4%bc%a0%e7%9a%84%e5%9d%91cors%e5%a4%a7%e5%b0%8f%e9%99%90%e5%88%b6%e8%bf%87%e6%9c%9f%e5%a4%9a%e6%96%87%e4%bb%b6" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>预签名上传出的问题，大多出在通知触发之前。下面这些，是我希望能在一页里看全的。</p>

<h3 class="relative group">CORS，只有浏览器需要
    <div id="cors只有浏览器需要" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#cors%e5%8f%aa%e6%9c%89%e6%b5%8f%e8%a7%88%e5%99%a8%e9%9c%80%e8%a6%81" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>原生应用不在乎这个。浏览器在 PUT 之前会先向 bucket 发一个预检 <code>OPTIONS</code>，除非 bucket 的 CORS 规则允许来自你的源的 <code>PUT</code> 并带上 <code>Content-Type</code> 头，否则上传会以 CORS 错误告终。Tigris 用的是标准的 S3 CORS 配置，所以规则写法和 AWS 上一样。预签名 PUT 用 <code>curl</code> 能通、在页面上不行时，第一个要查的就是它。</p>
<p><figure><span class="mc-img"><img
    class="my-0 rounded-md"
    loading="lazy"
    decoding="async"
    fetchpriority="auto"
    alt="Tigris bucket 设置的 CORS and headers 标签页：一条规则，允许来自两个源的 PUT 并带上 Content-Type 头"
    width="1204"
    height="671"
    src="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-bucket-cors_hu_7f61261034a8a56.webp"
    srcset="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-bucket-cors_hu_7f61261034a8a56.webp 800w, https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-bucket-cors_hu_3aa47360232f6475.webp 1280w"
    sizes="(min-width: 768px) 50vw, 65vw"
    data-zoom-src="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/tigris-bucket-cors_hu_3aa47360232f6475.webp"></span><figcaption>浏览器上传需要的 CORS 规则只有一条：你的源、PUT，以及签名所期望的 Content-Type 头。</figcaption></figure>
</p>

<h3 class="relative group">Content-Type 是签名的一部分
    <div id="content-type-是签名的一部分" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#content-type-%e6%98%af%e7%ad%be%e5%90%8d%e7%9a%84%e4%b8%80%e9%83%a8%e5%88%86" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>签名时带上 <code>ContentType</code>，意味着客户端必须原样发送这个头，否则 bucket 会回 403 <code>SignatureDoesNotMatch</code>。这就是槽位把 headers 和 URL 一起返回的原因。要有意识地签上它，但也要清楚它能换来什么：被强制的是头，不是内容，所以一个标着 <code>image/jpeg</code> 的 PDF 照样能进来。真正的检查在处理流程里；Pillow 拒绝打开不是图片的东西，那一行也就永远不会被标记为已处理。</p>

<h3 class="relative group">大小限制
    <div id="大小限制" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%a4%a7%e5%b0%8f%e9%99%90%e5%88%b6" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>预签名的 PUT URL 不带任何大小限制。如果你需要在字节落地之前就硬性拦住，用预签名 POST 配一个 <code>content-length-range</code> 策略条件可以做到。我没费这个劲，因为通知里带着对象的 <code>size</code>：handler 在读取之前先把超限的删掉，保存时那条路径最多只读上限加一个字节，够它判断就行。应用发的也就几百 KB；接近 15 MB 的东西，不会是我们的。</p>

<h3 class="relative group">过期
    <div id="过期" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e8%bf%87%e6%9c%9f" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>这里有两个时钟。预签名 URL 的有效期是十五分钟，做一次 PUT 绰绰有余，又短到泄露了也很快就没用。槽位那一行的有效期是两天，足够覆盖有人选好照片、把手机一放、第二天再把帖子写完的情况。客户端把挂了一天的待上传视为过期，直接重新申请一个，而不是抱着侥幸。</p>

<h3 class="relative group">多个文件，以及更大的文件
    <div id="多个文件以及更大的文件" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%a4%9a%e4%b8%aa%e6%96%87%e4%bb%b6%e4%bb%a5%e5%8f%8a%e6%9b%b4%e5%a4%a7%e7%9a%84%e6%96%87%e4%bb%b6" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>一个文件一个槽位。十张照片就是十个槽位、十个并行的 PUT，每一个都有自己的进度（<code>XMLHttpRequest</code> 有 <code>upload.onprogress</code>，<code>fetch</code> 没有），这是一个巨大的 base64 POST 给不了的。超过几 MB 就用分片上传（每个分片最小 5 MiB，所以它是给远大于这个数的文件准备的）：在服务器上创建 multipart upload，给每个 <code>upload_part</code> 预签名，分片都到齐后再完成它。上传完成时 Tigris 会发 <code>OBJECT_CREATED_MULTIPART</code>，同一个 handler 照样触发，其他什么都不用改。</p>

<h3 class="relative group">乱序
    <div id="乱序" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e4%b9%b1%e5%ba%8f" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>事件可能乱序到达，因为对象可能写入了不止一个区域。对上传来说无所谓：一个 key，一个事件。对会被覆盖的 key，相信 eTag 和对象的 <code>Last-Modified</code>，别相信 webhook 到你这里的先后顺序。</p>

<h2 class="relative group">同一个信号用在日志上：Discord 告警
    <div id="同一个信号用在日志上discord-告警" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%90%8c%e4%b8%80%e4%b8%aa%e4%bf%a1%e5%8f%b7%e7%94%a8%e5%9c%a8%e6%97%a5%e5%bf%97%e4%b8%8adiscord-%e5%91%8a%e8%ad%a6" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>bucket 一旦能跟后端说话，任何落进去的东西都能用同样的方式响应，我把它指向的第二样东西就是日志。</p>
<p>应用的日志以 gzip 压缩的小文件形式送进 bucket，每个应用大约五分钟一个。今年大部分时间里，一个按 15 分钟 cron 跑的 GitHub Actions workflow 用 DuckDB 读归档里最近 20 分钟的数据，找出慢请求的行，再往 Discord 发一份汇总。纸面上没毛病。实际上，平台一忙，GitHub 的定时 workflow 就不会准点跑，于是&quot;每 15 分钟&quot;更像是&quot;每隔几个小时&quot;，等它终于跑起来，要啃的时间窗口变大了，偶尔还会内存不足。我为了不让数据在两次运行之间漏掉而加的重叠窗口，又让同一个慢请求有时出现两次。就为了&quot;请求慢了告诉我一声&quot;，搭了这么一大套机器。</p>
<p>现在每个日志文件在落地时读一次，只读一次。它们 gzip 之后也就几 KB。handler 把慢请求的行挑出来，如果数量够多，或者有一个特别慢的，就通过 webhook 往一个 Discord 频道发一份汇总。一个文件里突然冒出一堆 5xx 也同样处理。从 Python 调 Discord webhook 就是一次请求：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">requests</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.conf</span> <span class="kn">import</span> <span class="n">settings</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">discord_alert</span><span class="p">(</span><span class="n">text</span><span class="p">:</span> <span class="nb">str</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="kc">None</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="n">requests</span><span class="o">.</span><span class="n">post</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="n">settings</span><span class="o">.</span><span class="n">DISCORD_WEBHOOK_URL</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">json</span><span class="o">=</span><span class="p">{</span><span class="s2">&#34;content&#34;</span><span class="p">:</span> <span class="n">text</span><span class="p">[:</span><span class="mi">1900</span><span class="p">]},</span>  <span class="c1"># Discord 单条消息上限 2000 字符</span>
</span></span><span class="line"><span class="cl">        <span class="n">timeout</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span></span></span></code></pre></div></div>
<p>没有 cron，没有重叠窗口，没有重复告警，而且告警会在请求发生后几分钟内到达，不用再等 GitHub 什么时候想起来。那个 Action 已经删了。</p>
<p>反正文件已经打开了，我顺便把里面的内容（错误、警告、健康检查）按小时计数，写进一张统计表。每日汇总以前要扫一整天的归档，现在只读几百行，只有统计出现缺口时才回头去扫归档。</p>

<h2 class="relative group">给删除加一道防线
    <div id="给删除加一道防线" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%bb%99%e5%88%a0%e9%99%a4%e5%8a%a0%e4%b8%80%e9%81%93%e9%98%b2%e7%ba%bf" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>这个是计划外的，有了 <code>OBJECT_DELETED</code> 事件之后自然就冒出来了。媒体文件被删除时，handler 会检查还有没有数据行指向它。如果有，那就是某处有 bug（或者有人在 bucket 控制台里手滑了），于是它清掉那一列，让应用显示占位图而不是一张裂开的图片，再把这事报告出来。</p>
<p>它还会按小时统计删除数量。正常的清理一小时也就删几个。要是哪天一小时里删了两三百个，我希望在事情发生的当下就知道，而不是等用户开始反馈照片变成空白。</p>

<h2 class="relative group">值得知道的几件事
    <div id="值得知道的几件事" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%80%bc%e5%be%97%e7%9f%a5%e9%81%93%e7%9a%84%e5%87%a0%e4%bb%b6%e4%ba%8b" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>响应要快。Tigris 给每次投递十秒。读一个 5 KB 的日志文件、处理一张手机照片都来得及；可能更久的活就丢进队列，view 直接返回 200，否则 Tigris 会超时重试，你又得回头去重。</p>
<p>在 bucket 那一层过滤。我的日志传送程序每个应用每隔几分钟就写一个文件，永不停歇。如果你只关心某一个前缀，就写进通知的过滤条件里，别让其他事情也把你的应用叫醒。</p>
<p>用假的请求体测试。payload 小而稳定，所以测试里直接带上正确的 <code>Authorization</code> 头，往 view 上 POST 一段 JSON，再断言 handler 做了什么。完全不用碰真实的存储。</p>
<p>别第一天就让它承重。这里的每一种用途都有后备方案：保存可以自己处理照片，每日汇总仍然可以扫描归档，应用仍然可以发 base64。通知让它们每一个都更快、更省，但哪个 webhook 丢了，也没有谁会因此倒下。</p>
<p>这周最爽的一刻，是删掉那个 workflow 文件。四十行 YAML、一个 Python 脚本、两个仓库 secret，外加隔三差五的一句&quot;告警怎么没响&quot;，全都没了，取而代之的是一个 handler：文件到了，读一个小文件，完事。不过重点还是上传。照片以网络允许的最快速度传上去，服务器对每一张仍然握有最终决定权，而且没有人需要在 bucket 和后端之间搭一座桥，因为 bucket 现在会自己说发生了什么。</p>
]]></content:encoded>
      <media:content url="https://jared.lynskey.co.nz/en/posts/2026/tigris-object-notifications/featured.jpg" medium="image" type="image/jpeg" />
    </item>
    <item>
      <title>不用 EAS，自建 Expo OTA 热更新：用 Django 和 Tigris 搭更新服务器</title>
      <link>https://jared.lynskey.co.nz/zh-cn/posts/2026/2026-02-22-self-hosted-ota-updates/</link>
      <guid isPermaLink="true">https://jared.lynskey.co.nz/zh-cn/posts/2026/2026-02-22-self-hosted-ota-updates/</guid>
      <pubDate>Sun, 22 Feb 2026 00:00:00 +0000</pubDate>
      <dc:creator>Jared Lynskey</dc:creator>
      <category>React Native</category>
      <category>Expo</category>
      <category>OTA Updates</category>
      <category>Django</category>
      <category>Mobile Development</category>
      <category>CI/CD</category>
      <category>Self-Hosted</category>
      <category>Tigris</category>
      <category>S3</category>
      <description>Expo 的 OTA 热更新是怎么工作的，以及我怎么不用 EAS Update 自己托管：一台实现 Expo Updates 协议的 Django REST 服务器，bundle 放在 Tigris S3 上，每月成本大约一美元。</description>
      <content:encoded><![CDATA[<blockquote><p><strong>2026 年 9 月 13 日更新。</strong> 这篇发出之后，Codemagic 发布了 <a href="https://patch.codemagic.io/"  target="_blank" rel="noreferrer sponsored">Patch</a>，一个 CodePush 路线的<a href="https://github.com/codemagic-ci-cd/codemagic-patch"  target="_blank" rel="noreferrer sponsored">开源</a>、可自托管 OTA 服务器。如果你是因为不想自己写服务器才找到这里的，它现在是一个实在的选项：我已经<a href="https://jared.lynskey.co.nz/zh-cn/posts/2026/2026-09-13-moving-to-codemagic-patch/" >把一个应用从下面这套方案迁到了 Patch</a>，并把过程写了下来，<a href="https://jared.lynskey.co.nz/zh-cn/posts/2026/2026-02-22-self-hosted-ota-updates/#%e5%86%99%e5%9c%a8%e6%9c%80%e5%90%8e" >写在最后</a>一节里也有一段简短说明。声明：那次迁移和那篇文章是 Codemagic 付费委托的，他们也希望在这里提一句。正文里的代码后来已精简为简短的示例。</p>
</blockquote><p>我做的报价应用，bug 修复都是通过 OTA 推送的：JavaScript 改动不用等 App Store 审核，直接下发到用户手机上。Expo 官方的 EAS Update 本来就能做这件事，但我还是用 Django REST Framework 和 Tigris S3 自己搭了一套。从那以后，iOS 和 Android 的更新全都走这台服务器。</p>
<p>Expo 的 OTA 更新（也就是大家常说的热更新）是这样运作的：应用里的 <code>expo-updates</code> 库向更新服务器请求一份清单，请求头里带着自己的平台和运行时版本。服务器返回最新的兼容更新，以及这次更新的 JavaScript bundle 和资源文件的地址，应用把它们下载下来，下次启动时就跑新的 bundle。EAS Update 是 Expo 官方托管的一种实现，但任何实现了这套协议的服务器都能用，我自己搭的就是这样一台。</p>
<p>这篇文章把整个方案过一遍：数据模型、清单（manifest）接口、发布流水线，还有那些只有真正跑起来才会踩到的坑。</p>

<h2 class="relative group">为什么要自己搭
    <div id="为什么要自己搭" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e4%b8%ba%e4%bb%80%e4%b9%88%e8%a6%81%e8%87%aa%e5%b7%b1%e6%90%ad" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>对我来说主要是钱的问题。EAS Update 按用量计费，用户多了、更新频繁了，账单就跟着涨；而 Tigris 这类 S3 兼容存储几乎不要钱。当然还有别的理由：有些行业要求应用资产必须留在自己的基础设施里；服务器在自己手上，整个更新流程就都可控，想按用户群灰度、想做 bundle 的 A/B 测试都行。另外，更新链路也不再受 Expo 服务可用性或下一次调价的影响。</p>

<h2 class="relative group">整体架构
    <div id="整体架构" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%95%b4%e4%bd%93%e6%9e%b6%e6%9e%84" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>一共四个部分：Django 后端负责下发更新清单、保存元数据；Tigris 存放 bundle 和资源文件本体；一个发布脚本负责导出、上传、登记更新；再加上移动应用本身，把更新地址指向我的服务器而不是 Expo 的。</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-text" data-lang="text"><span class="line"><span class="cl">┌─────────────────┐
</span></span><span class="line"><span class="cl">│   Mobile App    │
</span></span><span class="line"><span class="cl">│  (expo-updates) │
</span></span><span class="line"><span class="cl">└────────┬────────┘
</span></span><span class="line"><span class="cl">         │ 1. Request manifest
</span></span><span class="line"><span class="cl">         │    (with headers: platform, runtime-version)
</span></span><span class="line"><span class="cl">         ↓
</span></span><span class="line"><span class="cl">┌─────────────────┐
</span></span><span class="line"><span class="cl">│  Django Server  │
</span></span><span class="line"><span class="cl">│  /api/expo-     │◄─── 2. Query DB for latest update
</span></span><span class="line"><span class="cl">│   updates/      │
</span></span><span class="line"><span class="cl">│   manifest/     │
</span></span><span class="line"><span class="cl">└────────┬────────┘
</span></span><span class="line"><span class="cl">         │ 3. Generate presigned URLs
</span></span><span class="line"><span class="cl">         │
</span></span><span class="line"><span class="cl">         ↓
</span></span><span class="line"><span class="cl">┌─────────────────┐
</span></span><span class="line"><span class="cl">│   Tigris S3     │
</span></span><span class="line"><span class="cl">│  (Asset Files)  │◄─── 4. App downloads bundles directly
</span></span><span class="line"><span class="cl">└─────────────────┘</span></span></code></pre></div></div>

<h2 class="relative group">具体实现
    <div id="具体实现" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%85%b7%e4%bd%93%e5%ae%9e%e7%8e%b0" aria-label="锚点">#</a>
    </span>
    
</h2>

<h3 class="relative group">两个模型
    <div id="两个模型" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e4%b8%a4%e4%b8%aa%e6%a8%a1%e5%9e%8b" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>一切都建立在 <code>ExpoUpdate</code> 和 <code>ExpoUpdateAsset</code> 之上。前者保存每次更新的元数据：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="k">class</span> <span class="nc">ExpoUpdate</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="nb">id</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">UUIDField</span><span class="p">(</span><span class="n">primary_key</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="n">uuid</span><span class="o">.</span><span class="n">uuid4</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">runtime_version</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span> <span class="n">db_index</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">platform</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="n">max_length</span><span class="o">=</span><span class="mi">10</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">choices</span><span class="o">=</span><span class="p">[(</span><span class="s2">&#34;ios&#34;</span><span class="p">,</span> <span class="s2">&#34;iOS&#34;</span><span class="p">),</span> <span class="p">(</span><span class="s2">&#34;android&#34;</span><span class="p">,</span> <span class="s2">&#34;Android&#34;</span><span class="p">)],</span>
</span></span><span class="line"><span class="cl">        <span class="n">db_index</span><span class="o">=</span><span class="kc">True</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">is_active</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">BooleanField</span><span class="p">(</span><span class="n">default</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">db_index</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">manifest_data</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">JSONField</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">    <span class="n">description</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">TextField</span><span class="p">(</span><span class="n">blank</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">created_at</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DateTimeField</span><span class="p">(</span><span class="n">auto_now_add</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="n">indexes</span> <span class="o">=</span> <span class="p">[</span>
</span></span><span class="line"><span class="cl">            <span class="n">models</span><span class="o">.</span><span class="n">Index</span><span class="p">(</span><span class="n">fields</span><span class="o">=</span><span class="p">[</span><span class="s2">&#34;runtime_version&#34;</span><span class="p">,</span> <span class="s2">&#34;platform&#34;</span><span class="p">,</span> <span class="s2">&#34;is_active&#34;</span><span class="p">,</span> <span class="s2">&#34;-created_at&#34;</span><span class="p">])</span>
</span></span><span class="line"><span class="cl">        <span class="p">]</span></span></span></code></pre></div></div>
<p>这里有几个刻意的设计。<code>runtime_version</code> 对应 <code>app.json</code> 里的 <code>runtimeVersion</code>，客户端只会下载和自己运行时版本一致的更新，所以这个字段很关键。iOS 和 Android 的 bundle 不一样，所以分开存。<code>is_active</code> 是回滚开关：把有问题的更新停用，客户端就会退回上一个版本。<code>manifest_data</code> 直接把完整的 Expo Updates v1 协议清单存成 JSON，下发的时候取出来就行。</p>
<p><code>ExpoUpdateAsset</code> 记录每个文件：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="k">class</span> <span class="nc">ExpoUpdateAsset</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="nb">id</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">UUIDField</span><span class="p">(</span><span class="n">primary_key</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="n">uuid</span><span class="o">.</span><span class="n">uuid4</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">update</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">ForeignKey</span><span class="p">(</span><span class="n">ExpoUpdate</span><span class="p">,</span> <span class="n">on_delete</span><span class="o">=</span><span class="n">models</span><span class="o">.</span><span class="n">CASCADE</span><span class="p">,</span> <span class="n">related_name</span><span class="o">=</span><span class="s2">&#34;assets&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="nb">hash</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">255</span><span class="p">,</span> <span class="n">db_index</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">key</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">255</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">content_type</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">100</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">file_extension</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">10</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">file_path</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">500</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">file_size</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">(</span><span class="n">default</span><span class="o">=</span><span class="mi">0</span><span class="p">)</span></span></span></code></pre></div></div>
<p>资源用 SHA-256 哈希来引用，天然不可变、好缓存，同一个资源可以被多次更新复用。</p>

<h3 class="relative group">清单接口
    <div id="清单接口" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%b8%85%e5%8d%95%e6%8e%a5%e5%8f%a3" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>应用和服务器真正打交道的地方是 <code>/api/expo-updates/manifest/</code>，实现的是 <a href="https://docs.expo.dev/technical-specs/expo-updates-1/"  target="_blank" rel="noreferrer">Expo Updates v1 协议</a>：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="nd">@action</span><span class="p">(</span><span class="n">detail</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&#34;get&#34;</span><span class="p">],</span> <span class="n">url_path</span><span class="o">=</span><span class="s2">&#34;manifest&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">manifest</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="c1"># Extract required headers</span>
</span></span><span class="line"><span class="cl">    <span class="n">protocol_version</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">META</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;HTTP_EXPO_PROTOCOL_VERSION&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">platform</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">META</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;HTTP_EXPO_PLATFORM&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">runtime_version</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">META</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;HTTP_EXPO_RUNTIME_VERSION&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Validate protocol version</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="n">protocol_version</span> <span class="o">!=</span> <span class="s2">&#34;1&#34;</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">Response</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">            <span class="p">{</span><span class="s2">&#34;error&#34;</span><span class="p">:</span> <span class="sa">f</span><span class="s2">&#34;Unsupported protocol version: </span><span class="si">{</span><span class="n">protocol_version</span><span class="si">}</span><span class="s2">&#34;</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">            <span class="n">status</span><span class="o">=</span><span class="mi">400</span>
</span></span><span class="line"><span class="cl">        <span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Find latest active update for this runtime + platform</span>
</span></span><span class="line"><span class="cl">    <span class="n">update</span> <span class="o">=</span> <span class="n">ExpoUpdate</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="n">runtime_version</span><span class="o">=</span><span class="n">runtime_version</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">platform</span><span class="o">=</span><span class="n">platform</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">is_active</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span><span class="o">.</span><span class="n">order_by</span><span class="p">(</span><span class="s2">&#34;-created_at&#34;</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># No update available - client uses embedded bundle</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="ow">not</span> <span class="n">update</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="n">response</span> <span class="o">=</span> <span class="n">Response</span><span class="p">(</span><span class="n">status</span><span class="o">=</span><span class="mi">204</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">        <span class="n">response</span><span class="p">[</span><span class="s2">&#34;expo-protocol-version&#34;</span><span class="p">]</span> <span class="o">=</span> <span class="s2">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">response</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Generate presigned URLs for all assets</span>
</span></span><span class="line"><span class="cl">    <span class="n">manifest_data</span> <span class="o">=</span> <span class="n">build_manifest</span><span class="p">(</span><span class="n">update</span><span class="p">)</span>  <span class="c1"># fills in presigned asset URLs</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">Response</span><span class="p">(</span><span class="n">manifest_data</span><span class="p">,</span> <span class="n">status</span><span class="o">=</span><span class="mi">200</span><span class="p">)</span></span></span></code></pre></div></div>
<p>有三个细节值得注意。没有更新时返回 204，应用会继续用内置的 bundle。清单里的资源地址是预签名 URL，应用直接从 Tigris 的 CDN 下载，不用整个流经 Django。响应头里的 <code>expo-protocol-version</code> 不能省，客户端真的会检查。</p>

<h3 class="relative group">发布更新
    <div id="发布更新" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%8f%91%e5%b8%83%e6%9b%b4%e6%96%b0" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>发布靠一条 Django 管理命令，外面再包一层 shell 脚本。管理命令负责读取 <code>expo export</code> 的输出、给每个资源算 SHA-256 哈希、把 bundle 和资源并行传到 Tigris、写数据库记录，需要的话还会往桶里放一份用于生产同步的导入 JSON。精简到关键部分大致是这样：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">concurrent.futures</span> <span class="kn">import</span> <span class="n">ThreadPoolExecutor</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.db</span> <span class="kn">import</span> <span class="n">transaction</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">publish</span><span class="p">(</span><span class="n">platform</span><span class="p">,</span> <span class="n">runtime_version</span><span class="p">,</span> <span class="n">manifest</span><span class="p">,</span> <span class="n">files</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="c1"># Upload the bundle and assets in parallel (keys are content hashes)</span>
</span></span><span class="line"><span class="cl">    <span class="k">with</span> <span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">max_workers</span><span class="o">=</span><span class="mi">10</span><span class="p">)</span> <span class="k">as</span> <span class="n">executor</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="nb">list</span><span class="p">(</span><span class="n">executor</span><span class="o">.</span><span class="n">map</span><span class="p">(</span><span class="n">upload_asset</span><span class="p">,</span> <span class="n">files</span><span class="p">))</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Swap the active update in one transaction</span>
</span></span><span class="line"><span class="cl">    <span class="k">with</span> <span class="n">transaction</span><span class="o">.</span><span class="n">atomic</span><span class="p">():</span>
</span></span><span class="line"><span class="cl">        <span class="n">ExpoUpdate</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">            <span class="n">runtime_version</span><span class="o">=</span><span class="n">runtime_version</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">            <span class="n">platform</span><span class="o">=</span><span class="n">platform</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">            <span class="n">is_active</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="p">)</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">is_active</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">ExpoUpdate</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">create</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">            <span class="n">runtime_version</span><span class="o">=</span><span class="n">runtime_version</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">            <span class="n">platform</span><span class="o">=</span><span class="n">platform</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">            <span class="n">manifest_data</span><span class="o">=</span><span class="n">manifest</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="p">)</span></span></span></code></pre></div></div>
<p>平时真正敲的是外面这层脚本：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-bash" data-lang="bash"><span class="line"><span class="cl"><span class="c1"># Publish to local environment</span>
</span></span><span class="line"><span class="cl">./publish.sh ios
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># Publish to production</span>
</span></span><span class="line"><span class="cl">./publish.sh ios --production
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># Dry run to validate</span>
</span></span><span class="line"><span class="cl">./publish.sh --dry-run</span></span></code></pre></div></div>
<p>它会在导出前加载生产环境变量，平台可以只发一个也可以两个都发，还顺带处理下一节要讲的生产同步。</p>

<h3 class="relative group">同步到生产环境
    <div id="同步到生产环境" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%90%8c%e6%ad%a5%e5%88%b0%e7%94%9f%e4%ba%a7%e7%8e%af%e5%a2%83" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>我不想把生产环境的凭证放在自己笔记本上，所以生产发布分两步：先在本地发布（资源传到 Tigris，同时生成一份元数据的 JSON 快照），再带着 S3 路径调用生产环境的 API，让服务器自己把元数据导进去：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="nd">@action</span><span class="p">(</span><span class="n">detail</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">methods</span><span class="o">=</span><span class="p">[</span><span class="s2">&#34;post&#34;</span><span class="p">],</span> <span class="n">url_path</span><span class="o">=</span><span class="s2">&#34;import-update&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">import_update</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="c1"># Authenticate via Bearer token</span>
</span></span><span class="line"><span class="cl">    <span class="n">token</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">META</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;HTTP_AUTHORIZATION&#34;</span><span class="p">,</span> <span class="s2">&#34;&#34;</span><span class="p">)</span><span class="o">.</span><span class="n">removeprefix</span><span class="p">(</span><span class="s2">&#34;Bearer &#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="ow">not</span> <span class="n">hmac</span><span class="o">.</span><span class="n">compare_digest</span><span class="p">(</span><span class="n">token</span><span class="p">,</span> <span class="n">settings</span><span class="o">.</span><span class="n">IMPORT_TOKEN</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">Response</span><span class="p">({</span><span class="s2">&#34;error&#34;</span><span class="p">:</span> <span class="s2">&#34;Invalid token&#34;</span><span class="p">},</span> <span class="n">status</span><span class="o">=</span><span class="mi">401</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Download the import JSON from the bucket</span>
</span></span><span class="line"><span class="cl">    <span class="n">s3_key</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;s3_key&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">obj</span> <span class="o">=</span> <span class="n">s3_client</span><span class="o">.</span><span class="n">get_object</span><span class="p">(</span><span class="n">Bucket</span><span class="o">=</span><span class="n">bucket_name</span><span class="p">,</span> <span class="n">Key</span><span class="o">=</span><span class="n">s3_key</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">data</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">obj</span><span class="p">[</span><span class="s2">&#34;Body&#34;</span><span class="p">]</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Import into the production database</span>
</span></span><span class="line"><span class="cl">    <span class="k">with</span> <span class="n">transaction</span><span class="o">.</span><span class="n">atomic</span><span class="p">():</span>
</span></span><span class="line"><span class="cl">        <span class="n">update</span><span class="p">,</span> <span class="n">_</span> <span class="o">=</span> <span class="n">ExpoUpdate</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">update_or_create</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="n">data</span><span class="p">[</span><span class="s2">&#34;id&#34;</span><span class="p">],</span> <span class="n">defaults</span><span class="o">=</span><span class="p">{</span><span class="o">...</span><span class="p">})</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="n">asset_data</span> <span class="ow">in</span> <span class="n">data</span><span class="p">[</span><span class="s2">&#34;assets&#34;</span><span class="p">]:</span>
</span></span><span class="line"><span class="cl">            <span class="n">ExpoUpdateAsset</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">update_or_create</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="c1"># Clean up the import JSON</span>
</span></span><span class="line"><span class="cl">    <span class="n">s3_client</span><span class="o">.</span><span class="n">delete_object</span><span class="p">(</span><span class="n">Bucket</span><span class="o">=</span><span class="n">bucket_name</span><span class="p">,</span> <span class="n">Key</span><span class="o">=</span><span class="n">s3_key</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">Response</span><span class="p">({</span><span class="s2">&#34;update_id&#34;</span><span class="p">:</span> <span class="nb">str</span><span class="p">(</span><span class="n">update</span><span class="o">.</span><span class="n">id</span><span class="p">)})</span></span></span></code></pre></div></div>

<h3 class="relative group">让应用指向自己的服务器
    <div id="让应用指向自己的服务器" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e8%ae%a9%e5%ba%94%e7%94%a8%e6%8c%87%e5%90%91%e8%87%aa%e5%b7%b1%e7%9a%84%e6%9c%8d%e5%8a%a1%e5%99%a8" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>在 <code>app.json</code> 里配置更新地址和运行时版本：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-json" data-lang="json"><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="nt">&#34;expo&#34;</span><span class="p">:</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&#34;runtimeVersion&#34;</span><span class="p">:</span> <span class="s2">&#34;1.0.0&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&#34;updates&#34;</span><span class="p">:</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">      <span class="nt">&#34;url&#34;</span><span class="p">:</span> <span class="s2">&#34;https://api.example.com/api/expo-updates/manifest/&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre></div></div>
<p><code>runtimeVersion</code> 必须在应用和服务器之间严格对齐。改了原生代码或者升级了 Expo SDK，就把运行时版本加一，然后针对新版本重新发布更新。</p>

<h2 class="relative group">Tigris 存储
    <div id="tigris-存储" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#tigris-%e5%ad%98%e5%82%a8" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>Tigris 是 S3 兼容的对象存储，比 AWS S3 便宜得多，还自带全球边缘缓存。考虑到用户要下载好几 MB 的 bundle，这一点很实在。Django 侧的配置：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="c1"># settings.py</span>
</span></span><span class="line"><span class="cl"><span class="n">BUCKET_NAME</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s2">&#34;BUCKET_NAME&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">AWS_ENDPOINT_URL_S3</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s2">&#34;AWS_ENDPOINT_URL_S3&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">AWS_ACCESS_KEY_ID</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s2">&#34;AWS_ACCESS_KEY_ID&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">AWS_SECRET_ACCESS_KEY</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s2">&#34;AWS_SECRET_ACCESS_KEY&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">AWS_REGION</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s2">&#34;AWS_REGION&#34;</span><span class="p">,</span> <span class="s2">&#34;auto&#34;</span><span class="p">)</span></span></span></code></pre></div></div>
<p>客户端就是普通的 boto3：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">boto3</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">create_s3_client</span><span class="p">(</span><span class="n">endpoint_url</span><span class="p">,</span> <span class="n">region</span><span class="p">,</span> <span class="n">access_key</span><span class="p">,</span> <span class="n">secret_key</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">boto3</span><span class="o">.</span><span class="n">client</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">        <span class="s2">&#34;s3&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">endpoint_url</span><span class="o">=</span><span class="n">endpoint_url</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">region_name</span><span class="o">=</span><span class="n">region</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">aws_access_key_id</span><span class="o">=</span><span class="n">access_key</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">        <span class="n">aws_secret_access_key</span><span class="o">=</span><span class="n">secret_key</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="p">)</span></span></span></code></pre></div></div>
<p>下载走预签名 URL，应用直接从 CDN 拉取：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">presigned_url</span> <span class="o">=</span> <span class="n">s3_client</span><span class="o">.</span><span class="n">generate_presigned_url</span><span class="p">(</span>
</span></span><span class="line"><span class="cl">    <span class="s2">&#34;get_object&#34;</span><span class="p">,</span>
</span></span><span class="line"><span class="cl">    <span class="n">Params</span><span class="o">=</span><span class="p">{</span><span class="s2">&#34;Bucket&#34;</span><span class="p">:</span> <span class="n">bucket_name</span><span class="p">,</span> <span class="s2">&#34;Key&#34;</span><span class="p">:</span> <span class="n">asset</span><span class="o">.</span><span class="n">file_path</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="n">ExpiresIn</span><span class="o">=</span><span class="mi">3600</span><span class="p">,</span>  <span class="c1"># 1 hour</span>
</span></span><span class="line"><span class="cl"><span class="p">)</span></span></span></code></pre></div></div>

<h2 class="relative group">安全
    <div id="安全" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%ae%89%e5%85%a8" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>清单接口是故意不做鉴权的，因为应用在用户登录之前就需要拿更新。导入接口则完全不同：它能写生产数据库，所以要求共享密钥，并用常数时间比较来防时序攻击：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">IMPORT_TOKEN</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s2">&#34;IMPORT_TOKEN&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># Constant-time comparison prevents timing attacks</span>
</span></span><span class="line"><span class="cl"><span class="k">if</span> <span class="ow">not</span> <span class="n">hmac</span><span class="o">.</span><span class="n">compare_digest</span><span class="p">(</span><span class="n">token</span><span class="p">,</span> <span class="n">IMPORT_TOKEN</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="n">Response</span><span class="p">({</span><span class="s2">&#34;error&#34;</span><span class="p">:</span> <span class="s2">&#34;Invalid token&#34;</span><span class="p">},</span> <span class="n">status</span><span class="o">=</span><span class="mi">401</span><span class="p">)</span></span></span></code></pre></div></div>
<p>资源完整性是这套设计白送的：所有资源都按 SHA-256 哈希校验，被篡改的资源直接失败。预签名 URL 一小时过期，bundle 也就不会被长期盗链。</p>

<h2 class="relative group">性能
    <div id="性能" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%80%a7%e8%83%bd" aria-label="锚点">#</a>
    </span>
    
</h2>
<p><code>(runtime_version, platform, is_active, -created_at)</code> 这个联合索引保证清单查询不会随着更新数量增长变慢：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="n">indexes</span> <span class="o">=</span> <span class="p">[</span>
</span></span><span class="line"><span class="cl">        <span class="n">models</span><span class="o">.</span><span class="n">Index</span><span class="p">(</span><span class="n">fields</span><span class="o">=</span><span class="p">[</span><span class="s2">&#34;runtime_version&#34;</span><span class="p">,</span> <span class="s2">&#34;platform&#34;</span><span class="p">,</span> <span class="s2">&#34;is_active&#34;</span><span class="p">,</span> <span class="s2">&#34;-created_at&#34;</span><span class="p">])</span>
</span></span><span class="line"><span class="cl">    <span class="p">]</span></span></span></code></pre></div></div>
<p>发布脚本用线程池并行上传资源：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="k">with</span> <span class="n">ThreadPoolExecutor</span><span class="p">(</span><span class="n">max_workers</span><span class="o">=</span><span class="mi">10</span><span class="p">)</span> <span class="k">as</span> <span class="n">executor</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="n">futures</span> <span class="o">=</span> <span class="p">{</span><span class="n">executor</span><span class="o">.</span><span class="n">submit</span><span class="p">(</span><span class="n">upload_asset</span><span class="p">,</span> <span class="n">asset</span><span class="p">):</span> <span class="n">asset</span> <span class="k">for</span> <span class="n">asset</span> <span class="ow">in</span> <span class="n">assets</span><span class="p">}</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="n">future</span> <span class="ow">in</span> <span class="n">as_completed</span><span class="p">(</span><span class="n">futures</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">        <span class="c1"># Track progress</span></span></span></code></pre></div></div>
<p>以一次 50 个资源左右的典型更新为例，发布时间从大约 2 分钟缩到了 15 秒。分发这边什么都不用做，Tigris 会自动把资源缓存到离用户近的边缘节点。</p>

<h2 class="relative group">日常流程
    <div id="日常流程" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%97%a5%e5%b8%b8%e6%b5%81%e7%a8%8b" aria-label="锚点">#</a>
    </span>
    
</h2>

<h3 class="relative group">开发时
    <div id="开发时" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%bc%80%e5%8f%91%e6%97%b6" aria-label="锚点">#</a>
    </span>
    
</h3>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-bash" data-lang="bash"><span class="line"><span class="cl"><span class="c1"># 1. Make code changes in the app</span>
</span></span><span class="line"><span class="cl">git commit -am <span class="s2">&#34;Fix bug&#34;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># 2. Publish OTA update to local environment</span>
</span></span><span class="line"><span class="cl">./publish.sh ios
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># 3. Test on device</span>
</span></span><span class="line"><span class="cl"><span class="c1"># App automatically downloads and applies update</span></span></span></code></pre></div></div>

<h3 class="relative group">发布到生产
    <div id="发布到生产" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%8f%91%e5%b8%83%e5%88%b0%e7%94%9f%e4%ba%a7" aria-label="锚点">#</a>
    </span>
    
</h3>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-bash" data-lang="bash"><span class="line"><span class="cl"><span class="c1"># 1. Publish to production</span>
</span></span><span class="line"><span class="cl">./publish.sh ios --production
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># 2. Monitor</span>
</span></span><span class="line"><span class="cl"><span class="c1"># Check Django admin for update records</span>
</span></span><span class="line"><span class="cl"><span class="c1"># Verify assets in Tigris dashboard</span></span></span></code></pre></div></div>

<h3 class="relative group">回滚
    <div id="回滚" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%9b%9e%e6%bb%9a" aria-label="锚点">#</a>
    </span>
    
</h3>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-bash" data-lang="bash"><span class="line"><span class="cl"><span class="c1"># Mark problematic update as inactive in Django admin</span>
</span></span><span class="line"><span class="cl"><span class="c1"># or via management shell:</span>
</span></span><span class="line"><span class="cl">python manage.py shell
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">&gt;&gt;&gt; from updates.models import ExpoUpdate
</span></span><span class="line"><span class="cl">&gt;&gt;&gt; <span class="nv">bad_update</span> <span class="o">=</span> ExpoUpdate.objects.get<span class="o">(</span><span class="nv">id</span><span class="o">=</span><span class="s2">&#34;uuid-here&#34;</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">&gt;&gt;&gt; bad_update.is_active <span class="o">=</span> False
</span></span><span class="line"><span class="cl">&gt;&gt;&gt; bad_update.save<span class="o">()</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># Clients will now receive the previous active update</span></span></span></code></pre></div></div>

<h2 class="relative group">成本
    <div id="成本" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%88%90%e6%9c%ac" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>这个应用大约有 500 个活跃用户。Tigris 上，约 200 MB 的历史更新每月大概 0.02 美元，更新下载带来的每月约 50 GB 流出流量大概 1 美元。Django 这边跑在原本就承载 API 的服务器上，没有额外成本。加起来每月一美元左右。同样的用量放到 EAS Update 上，一年大概要 300 到 500 美元，所以这套东西基本上立刻就回本了。</p>

<h2 class="relative group">监控与调试
    <div id="监控与调试" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%9b%91%e6%8e%a7%e4%b8%8e%e8%b0%83%e8%af%95" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>没什么花哨的。ViewSet 会把每个清单请求记进日志：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">logger</span><span class="o">.</span><span class="n">info</span><span class="p">(</span><span class="sa">f</span><span class="s2">&#34;Manifest request: platform=</span><span class="si">{</span><span class="n">platform</span><span class="si">}</span><span class="s2">, runtime=</span><span class="si">{</span><span class="n">runtime_version</span><span class="si">}</span><span class="s2">&#34;</span><span class="p">)</span></span></span></code></pre></div></div>
<p>Django admin 就是事实上的控制台，把模型注册进去，查看、筛选都很方便：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="nd">@admin.register</span><span class="p">(</span><span class="n">ExpoUpdate</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="k">class</span> <span class="nc">ExpoUpdateAdmin</span><span class="p">(</span><span class="n">admin</span><span class="o">.</span><span class="n">ModelAdmin</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="n">list_display</span> <span class="o">=</span> <span class="p">[</span><span class="s2">&#34;platform&#34;</span><span class="p">,</span> <span class="s2">&#34;runtime_version&#34;</span><span class="p">,</span> <span class="s2">&#34;is_active&#34;</span><span class="p">,</span> <span class="s2">&#34;created_at&#34;</span><span class="p">]</span>
</span></span><span class="line"><span class="cl">    <span class="n">list_filter</span> <span class="o">=</span> <span class="p">[</span><span class="s2">&#34;platform&#34;</span><span class="p">,</span> <span class="s2">&#34;is_active&#34;</span><span class="p">,</span> <span class="s2">&#34;runtime_version&#34;</span><span class="p">]</span>
</span></span><span class="line"><span class="cl">    <span class="n">search_fields</span> <span class="o">=</span> <span class="p">[</span><span class="s2">&#34;description&#34;</span><span class="p">]</span></span></span></code></pre></div></div>
<p>客户端这边，<code>expo-updates</code> 会告诉你它看到了什么：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-typescript" data-lang="typescript"><span class="line"><span class="cl"><span class="kr">import</span> <span class="o">*</span> <span class="kr">as</span> <span class="nx">Updates</span> <span class="kr">from</span> <span class="s1">&#39;expo-updates&#39;</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="nx">Updates</span><span class="p">.</span><span class="nx">checkForUpdateAsync</span><span class="p">().</span><span class="nx">then</span><span class="p">(</span><span class="nx">update</span> <span class="o">=&gt;</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="s1">&#39;Update available:&#39;</span><span class="p">,</span> <span class="nx">update</span><span class="p">.</span><span class="nx">isAvailable</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">  <span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="s1">&#39;Manifest:&#39;</span><span class="p">,</span> <span class="nx">update</span><span class="p">.</span><span class="nx">manifest</span><span class="p">);</span>
</span></span><span class="line"><span class="cl"><span class="p">});</span></span></span></code></pre></div></div>

<h2 class="relative group">踩过的坑
    <div id="踩过的坑" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e8%b8%a9%e8%bf%87%e7%9a%84%e5%9d%91" aria-label="锚点">#</a>
    </span>
    
</h2>

<h3 class="relative group">运行时版本不匹配
    <div id="运行时版本不匹配" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e8%bf%90%e8%a1%8c%e6%97%b6%e7%89%88%e6%9c%ac%e4%b8%8d%e5%8c%b9%e9%85%8d" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>最常见的故障也最安静：客户端只下载和自己运行时版本一致的更新。装机版本还在 <code>1.0.0</code>，你却按 <code>1.0.1</code> 发布，那就什么都收不到，也没有任何报错。运行时版本要和构建保持同步，只在原生代码变化时才递增。</p>

<h3 class="relative group">createdAt 时间戳
    <div id="createdat-时间戳" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#createdat-%e6%97%b6%e9%97%b4%e6%88%b3" aria-label="锚点">#</a>
    </span>
    
</h3>
<p><code>expo-updates</code> 客户端会拿清单的 <code>createdAt</code> 和内置 bundle 的 <code>commitTime</code> 比较，只有 <code>createdAt</code> 更新的才会被应用。ViewSet 里用数据库时间戳覆盖它：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">manifest_data</span><span class="p">[</span><span class="s2">&#34;createdAt&#34;</span><span class="p">]</span> <span class="o">=</span> <span class="n">update</span><span class="o">.</span><span class="n">created_at</span><span class="o">.</span><span class="n">strftime</span><span class="p">(</span><span class="s2">&#34;%Y-%m-</span><span class="si">%d</span><span class="s2">T%H:%M:%S.</span><span class="si">%f</span><span class="s2">Z&#34;</span><span class="p">)</span></span></span></code></pre></div></div>
<p>本地开发时，如果你在发布 OTA <em>之后</em>又构建了二进制包，就重新发布一次 OTA，保证时间戳更新。</p>

<h3 class="relative group">清单里的资源 <code>key</code>
    <div id="清单里的资源-key" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%b8%85%e5%8d%95%e9%87%8c%e7%9a%84%e8%b5%84%e6%ba%90-key" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>清单中每个资源的 <code>key</code> 字段是 <code>expo-updates</code> 用来做缓存的，它必须是确定性哈希（比如文件名的 MD5），不能是随机 UUID 或随便一个字符串。搞错了，客户端可能无法正确缓存和读取资源，更新会在第一次成功加载之后悄悄失效。感谢读者 Raphael Mutschler 指出这个问题。在找到原因之前，他的更新恰好只成功过一次。</p>

<h3 class="relative group"><code>expoClient</code> 里的应用配置
    <div id="expoclient-里的应用配置" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#expoclient-%e9%87%8c%e7%9a%84%e5%ba%94%e7%94%a8%e9%85%8d%e7%bd%ae" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>如果应用用到 <code>Linking</code>、<code>Constants</code> 或其他在运行时读取应用配置的东西，清单的 <code>extra.expoClient</code> 字段里就必须带上应用配置。少了它，应用第一次可能启动正常，关掉之后再打开就崩溃或干脆打不开。原因是 <code>expo-updates</code> 会用 OTA 的清单替换内置清单，<code>expoClient</code> 一缺，这些 API 依赖的配置就没了。这个坑也是 Raphael Mutschler 发现的。</p>

<h3 class="relative group">清理旧资源
    <div id="清理旧资源" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%b8%85%e7%90%86%e6%97%a7%e8%b5%84%e6%ba%90" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>旧更新会在 Tigris 里越积越多。目前我还是手动清理：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="c1"># Delete updates older than 30 days</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">timedelta</span>
</span></span><span class="line"><span class="cl"><span class="kn">from</span> <span class="nn">django.utils</span> <span class="kn">import</span> <span class="n">timezone</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="n">cutoff</span> <span class="o">=</span> <span class="n">timezone</span><span class="o">.</span><span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">timedelta</span><span class="p">(</span><span class="n">days</span><span class="o">=</span><span class="mi">30</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">old_updates</span> <span class="o">=</span> <span class="n">ExpoUpdate</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">created_at__lt</span><span class="o">=</span><span class="n">cutoff</span><span class="p">,</span> <span class="n">is_active</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="k">for</span> <span class="n">update</span> <span class="ow">in</span> <span class="n">old_updates</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="c1"># Delete assets from S3</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="n">asset</span> <span class="ow">in</span> <span class="n">update</span><span class="o">.</span><span class="n">assets</span><span class="o">.</span><span class="n">all</span><span class="p">():</span>
</span></span><span class="line"><span class="cl">        <span class="n">s3_client</span><span class="o">.</span><span class="n">delete_object</span><span class="p">(</span><span class="n">Bucket</span><span class="o">=</span><span class="n">bucket_name</span><span class="p">,</span> <span class="n">Key</span><span class="o">=</span><span class="n">asset</span><span class="o">.</span><span class="n">file_path</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="c1"># Delete DB records</span>
</span></span><span class="line"><span class="cl">    <span class="n">update</span><span class="o">.</span><span class="n">delete</span><span class="p">()</span></span></span></code></pre></div></div>
<p>按理说应该放进定时任务，我还没顾上。</p>

<h2 class="relative group">接下来想加的
    <div id="接下来想加的" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e6%8e%a5%e4%b8%8b%e6%9d%a5%e6%83%b3%e5%8a%a0%e7%9a%84" aria-label="锚点">#</a>
    </span>
    
</h2>
<p><em>（2026 年 9 月：这三样 Patch 现在都有了，还不止，见<a href="https://jared.lynskey.co.nz/zh-cn/posts/2026/2026-09-13-moving-to-codemagic-patch/" >迁移记录</a>。）</em></p>

<h3 class="relative group">灰度发布
    <div id="灰度发布" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e7%81%b0%e5%ba%a6%e5%8f%91%e5%b8%83" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>加一个 <code>rollout_percentage</code> 字段，就能先放量给一部分用户：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">rollout_percentage</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">(</span><span class="n">default</span><span class="o">=</span><span class="mi">100</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># In the manifest view:</span>
</span></span><span class="line"><span class="cl"><span class="k">if</span> <span class="n">update</span><span class="o">.</span><span class="n">rollout_percentage</span> <span class="o">&lt;</span> <span class="mi">100</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">    <span class="c1"># Hash user ID and check if they&#39;re in rollout group</span>
</span></span><span class="line"><span class="cl">    <span class="n">user_hash</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">hashlib</span><span class="o">.</span><span class="n">sha256</span><span class="p">(</span><span class="n">user_id</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span><span class="o">.</span><span class="n">hexdigest</span><span class="p">(),</span> <span class="mi">16</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="k">if</span> <span class="p">(</span><span class="n">user_hash</span> <span class="o">%</span> <span class="mi">100</span><span class="p">)</span> <span class="o">&gt;=</span> <span class="n">update</span><span class="o">.</span><span class="n">rollout_percentage</span><span class="p">:</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="n">Response</span><span class="p">(</span><span class="n">status</span><span class="o">=</span><span class="mi">204</span><span class="p">)</span>  <span class="c1"># No update</span></span></span></code></pre></div></div>

<h3 class="relative group">区分预发环境
    <div id="区分预发环境" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%8c%ba%e5%88%86%e9%a2%84%e5%8f%91%e7%8e%af%e5%a2%83" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>加一个 <code>environment</code> 字段，预发构建和生产就能收到不同的更新：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="n">environment</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">20</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="s2">&#34;production&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="c1"># Client sends environment in custom header</span>
</span></span><span class="line"><span class="cl"><span class="n">environment</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">META</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">&#34;HTTP_X_UPDATE_ENVIRONMENT&#34;</span><span class="p">,</span> <span class="s2">&#34;production&#34;</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">update</span> <span class="o">=</span> <span class="n">ExpoUpdate</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">environment</span><span class="o">=</span><span class="n">environment</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span></span></span></code></pre></div></div>

<h3 class="relative group">下载统计
    <div id="下载统计" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e4%b8%8b%e8%bd%bd%e7%bb%9f%e8%ae%a1" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>再加一个小模型，就能认真回答“这次更新到底有没有人收到”：</p>
<div class="highlight-wrapper"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python"><span class="line"><span class="cl"><span class="k">class</span> <span class="nc">ExpoUpdateDownload</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
</span></span><span class="line"><span class="cl">    <span class="n">update</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">ForeignKey</span><span class="p">(</span><span class="n">ExpoUpdate</span><span class="p">,</span> <span class="n">on_delete</span><span class="o">=</span><span class="n">models</span><span class="o">.</span><span class="n">CASCADE</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">user_id</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">255</span><span class="p">,</span> <span class="n">null</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">platform</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">10</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">    <span class="n">downloaded_at</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DateTimeField</span><span class="p">(</span><span class="n">auto_now_add</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span></span></span></code></pre></div></div>

<h2 class="relative group">写在最后
    <div id="写在最后" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%86%99%e5%9c%a8%e6%9c%80%e5%90%8e" aria-label="锚点">#</a>
    </span>
    
</h2>
<p>整套系统就是两个 Django 模型、几个视图、一个发布脚本，外加每月一美元的基础设施。比我动手前预想的要小，而且从那以后一直安安静静地支撑着这个应用的两个平台。</p>
<p>上面的代码是从那个生产应用简化出来的示例，按自己的项目改改就能用。读者 Raphael Mutschler 还发布了一个独立实现 <a href="https://github.com/mutschler/expo-ota-server"  target="_blank" rel="noreferrer">expo-ota-server</a>，想从能直接跑的代码开始的话可以去看看。</p>

<h3 class="relative group">如果你不想自己写服务器
    <div id="如果你不想自己写服务器" class="anchor"></div>
    
    <span
        class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none">
        <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#%e5%a6%82%e6%9e%9c%e4%bd%a0%e4%b8%8d%e6%83%b3%e8%87%aa%e5%b7%b1%e5%86%99%e6%9c%8d%e5%8a%a1%e5%99%a8" aria-label="锚点">#</a>
    </span>
    
</h3>
<p>这篇写完之后出现了两样东西，不用 Django 也能覆盖同样的地盘。第一个是上面提到的 Raphael 的 <code>expo-ota-server</code>。第二个是 <a href="https://patch.codemagic.io/"  target="_blank" rel="noreferrer sponsored">Codemagic Patch</a>：<a href="https://github.com/codemagic-ci-cd/codemagic-patch"  target="_blank" rel="noreferrer sponsored">开源</a>，通过 Docker Compose 安装跑在你自己的机器上，走的是 CodePush 协议而不是 Expo Updates 协议，所以你要把 <code>expo-updates</code> 换成它的 SDK，把 <code>eas update</code> 换成 <code>cmpatch release-react</code>。它能用 S3 兼容存储，所以本文这样的 Tigris 桶也照样能用。</p>
<p>它开箱就带着我在“接下来想加的”里列出来、却一直没做的那些：Staging 和 Production 两套 deployment、按百分比灰度、每个 release 的下载和安装数字、强制更新、二进制 patch、代码签名，以及新 bundle 在应用报告就绪之前崩溃时设备端的回滚。代价是，在任何人收到 Patch 更新之前先要发一个新的原生二进制，因为 SDK 得进到应用里；还有一台要跑的服务器，取代了一条管理命令。</p>
<p>我把自己的一个应用，连同已提交的原生工程和真实的发布流水线，从本文这套方案迁到了 Patch。<a href="https://jared.lynskey.co.nz/zh-cn/posts/2026/2026-09-13-moving-to-codemagic-patch/" >那篇记录</a>写了哪些顺利、哪些不顺，以及到底有多难。Codemagic 赞助了那项工作，并对它做了一轮事实审阅，不是编辑审阅。</p>
<hr>
<p><em>完整规范见 <a href="https://docs.expo.dev/technical-specs/expo-updates-1/"  target="_blank" rel="noreferrer">Expo Updates Protocol Specification</a>。</em></p>
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