7.4 Service Bindings 與 Queue#

# wrangler.toml（呼叫者這邊）
[[services]]
binding = "AUTH"
service = "auth-worker"
# environment = "production"   # 可指向特定 env

// 主 Worker：把「簽 token」外包給 auth-worker
export default {
  async fetch(req: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    if (req.url.includes("/token")) {
      // 不是 HTTP；這是呼叫另一個 Worker 的 fetch
      const res = await env.AUTH.fetch("https://internal/token", {
        method: "POST", body: JSON.stringify({ userId: "u-123" }),
      });
      return new Response(await res.text());
    }
    return new Response("ok");
  },
};

// auth-worker（被呼者）：像一般 fetch handler
export default {
  async fetch(req: Request): Promise<Response> {
    const { userId } = await req.json();
    return Response.json({ token: await signToken(userId) });
  },
};

# wrangler.toml（生產者側）
[[queues.producers]]
binding = "MAIL_QUEUE"
queue = "signup-emails"

# （消費者側，另一個 Worker 的 wrangler.toml）
# [[queues.consumers]]
# queue = "signup-emails"
# max_retries = 3
# dead_letter_queue = "signup-emails-dlq"
# max_batch_size = 10

// signup-worker.ts：Producer
export default {
  async fetch(req: Request, env: Env): Promise<Response> {
    if (req.method === "POST" && new URL(req.url).pathname === "/signup") {
      const { email } = await req.json();
      await env.DB.prepare("INSERT INTO users(email) VALUES (?)").bind(email).run();

      // 1) 立刻回應使用者（不等寄信）
      // 2) 把「寄信」這件事丟進佇列
      await env.MAIL_QUEUE.send({
        type: "welcome_email",
        email,
        userId: crypto.randomUUID(),
      });
      return Response.json({ ok: true }, { status: 201 });
    }
    return new Response("not found", { status: 404 });
  },
};

// mail-worker.ts：Consumer
export default {
  async queue(batch: MessageBatch<any>, env: Env): Promise<void> {
    for (const msg of batch.messages) {
      if (msg.body.type === "welcome_email") {
        await sendEmail(env, msg.body.email, `
          <h1>歡迎加入！</h1>
          <p>你的帳號已建立完成。</p>`);
        msg.ack();                              // 明示成功，訊息移除
      } else {
        msg.retry({ delaySeconds: 60 });        // 失敗，等 60 秒再投遞
      }
    }
  },
};

async function sendEmail(env: Env, to: string, html: string) {
  // MailChannels / Resend / Mailgun 等，本書以第三方 API 為例
  const res = await fetch("https://api.mailchannels.net/tx/v1/send", {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify({
      personalizations: [{ to: [{ email: to }] }],
      from: { email: "noreply@your.domain", name: "CCCBook" },
      subject: "歡迎！",
      content: [{ type: "text/html", value: html }],
    }),
  });
  if (!res.ok) throw new Error(`mail failed: ${res.status}`);
}

// 至少一次語意的保險
const done = await env.DB.prepare("SELECT 1 FROM sent_emails WHERE user_id=?")
  .bind(msg.body.userId).first();
if (done) { msg.ack(); continue; }
await sendEmail(env, msg.body.email, html);
await env.DB.prepare("INSERT INTO sent_emails(user_id) VALUES (?)").bind(msg.body.userId).run();
msg.ack();