Edge Computing with Cloudflare Workers & Deno · レッスン

Denoによるデータベースプロキシ

DenoとWorkersを使って効率的なデータベースプロキシを作成し、従来型またはサーバーレスのデータベースに接続します

「Denoによるデータベースプロキシ」はCoddyKit上の無料Edge Computing with Cloudflare Workers & Denoレッスンです。これはレッスン3/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはEdge Computing with Cloudflare Workers & Deno学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Edge Computing with Cloudflare Workers & Denoコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

What are Database Proxies?

Welcome to our lesson on Deno database proxies! An edge database proxy acts as an intermediary layer between your application (like a Cloudflare Worker) and your database.

Instead of your edge function connecting directly to the database, it talks to the proxy. The proxy then handles the actual database connection.

Why use them? They centralize connection management, enhance security, and enable data transformation before reaching your database.

Why Deno for Proxies?

Deno is an excellent choice for building these database proxies at the edge. Here's why:

Native HTTP Server: Deno has a powerful, built-in web server, perfect for handling proxy requests.
Security Model: Its granular permission system means you explicitly grant network or file access, enhancing security.
Performance: Deno's fast startup times and efficient runtime make it suitable for responsive proxy services.
TypeScript First: Built-in TypeScript support helps you write more robust and maintainable code for your proxy logic.

Your First Deno Proxy Server

Let's start by creating a basic Deno HTTP server. This server will listen for incoming requests and respond with a simple message, acting as the foundation for our proxy.

Try running this example:

Deno.serve(async (req) => {
  const url = new URL(req.url);
  if (url.pathname === "/") {
    return new Response("Deno Proxy is running!", { status: 200 });
  }
  return new Response("Not Found", { status: 404 });
}, { port: 8000 });

console.log("Deno proxy listening on http://localhost:8000");

Forwarding Requests to DB

Now, let's modify our Deno proxy to forward incoming requests to a 'mock' database endpoint. In a real scenario, this would be your actual database API or a service that interacts with it.

Here, we use a public JSONPlaceholder API to simulate a database call.

Deno.serve(async (req) => {
  // Mock database endpoint (e.g., a public API)
  const mockDbApi = "https://jsonplaceholder.typicode.com/posts";
  const url = new URL(req.url);

  // Construct the target URL for the actual database call
  let targetUrl = mockDbApi;
  if (url.pathname !== "/") {
    targetUrl += url.pathname; // Append path for specific resources
  }

  const proxyReq = new Request(targetUrl, {
    method: req.method,
    headers: req.headers, // Pass original headers
    body: req.body,       // Pass original body
  });

  try {
    const dbResponse = await fetch(proxyReq);
    // Add a custom header to indicate proxy processing
    const newResponse = new Response(dbResponse.body, dbResponse);
    newResponse.headers.set("X-Proxy-By", "Deno");
    return newResponse;
  } catch (error) {
    return new Response(`Proxy Error: ${error.message}`, { status: 500 });
  }
}, { port: 8000 });

console.log("Deno proxy forwarding on http://localhost:8000");

The Need for Connection Pooling

Database connections are expensive to establish. Serverless functions, like Cloudflare Workers, are often short-lived and stateless. If each Worker instance opens a new connection, you can quickly exhaust database connection limits.

Connection pooling is a technique where a pool of open, reusable database connections is maintained. When a request comes in, a connection is borrowed from the pool instead of creating a new one.

Proxy's Role in Pooling

A Deno database proxy can effectively manage connection pooling. Unlike ephemeral Workers, a Deno proxy (e.g., deployed on Deno Deploy or a persistent server) can be a long-lived process.

This allows it to maintain and manage a pool of database connections, serving multiple requests from various Workers without constantly opening and closing connections. This significantly reduces overhead and improves database performance and stability.

Secure Your Database Proxy

Security is paramount. Your Deno proxy acts as a gateway to your database, so it must be secured:

Hide Credentials: Never expose raw database credentials in your Worker code. The proxy should store and use these securely.
Authentication for Proxy: Implement authentication (e.g., API keys, JWTs) for your Workers to access the proxy itself. This ensures only authorized edge functions can send requests.
Permissions: Deno's explicit permission model helps. Only grant the proxy network access to your database, not arbitrary internet access.

Transforming Data at the Edge

Beyond just forwarding, a Deno proxy can transform data. This means modifying request bodies before sending them to the database or altering responses before returning them to the Worker.

This is useful for adding metadata, filtering sensitive information, or normalizing data formats.

Deno.serve(async (req) => {
  const mockDbApi = "https://jsonplaceholder.typicode.com/posts";
  const url = new URL(req.url);
  let targetUrl = mockDbApi;

  // Only transform POST requests for simplicity
  if (req.method === "POST") {
    let requestBody = await req.json(); // Assuming JSON body
    requestBody.processedAt = new Date().toISOString(); // Add a timestamp
    requestBody.source = "edge-proxy"; // Add a source identifier

    const proxyReq = new Request(targetUrl, {
      method: req.method,
      headers: {
        ...req.headers,
        "Content-Type": "application/json" // Ensure correct type
      },
      body: JSON.stringify(requestBody), // Send modified body
    });
    const dbResponse = await fetch(proxyReq);
    return new Response(dbResponse.body, dbResponse);
  } else {
    // For other methods, just forward
    const dbResponse = await fetch(new Request(targetUrl, req));
    return new Response(dbResponse.body, dbResponse);
  }
}, { port: 8000 });

console.log("Deno proxy with data transformation on http://localhost:8000");

Worker to Deno Proxy Flow

How would a Cloudflare Worker interact with this Deno proxy?

The Worker would simply make a standard HTTP fetch request to the Deno proxy's endpoint. If your Deno proxy is deployed on a platform like Deno Deploy, it will have a public URL.

The Worker sends its request, the Deno proxy processes it (e.g., handles pooling, adds security, transforms data), and then forwards it to the actual database, returning the database's response to the Worker.

Deno Proxy Benefits?

Which of the following are benefits of using a Deno-based database proxy at the edge?

Lesson Summary

In this lesson, we explored how to create efficient database proxies using Deno. We learned that Deno's native HTTP server and security model make it ideal for this task.

We built a basic proxy that forwards requests.
Understood the importance of connection pooling and the proxy's role in it.
Discussed securing your proxy and transforming data at the edge.
Finally, we saw how Cloudflare Workers can interact with such a proxy.

This pattern provides a powerful way to manage database interactions from your edge applications.

よくある質問

「Denoによるデータベースプロキシ」レッスンは無料ですか？

はい。「Denoによるデータベースプロキシ」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Edge Computing with Cloudflare Workers & Denoコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Edge Computing with Cloudflare Workers & Denoコースには全4レッスンが含まれています。

「Denoによるデータベースプロキシ」で何を学びますか？

DenoとWorkersを使って効率的なデータベースプロキシを作成し、従来型またはサーバーレスのデータベースに接続しますブラウザで直接実行するハンズオンコードでEdge Computing with Cloudflare Workers & Denoを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Edge Computing with Cloudflare Workers & Denoを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのEdge Computing with Cloudflare Workers & Denoは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン3/4です。

「Denoによるデータベースプロキシ」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このEdge Computing with Cloudflare Workers & Denoレッスンでコードを書いて実行できますか？

はい。すべてのEdge Computing with Cloudflare Workers & Denoレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

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