Algolia cache proxy - Cloudflare worker

algolia_cache_proxy_for_cloudflare.js

const ALGOLIA_APP_ID = "<your algolia app id>";

addEventListener('fetch', event => {
  try {
    const request = event.request;
    if (request.method.toUpperCase() === 'POST') return event.respondWith(handlePostRequest(event));
    return handleRequest(request);
  } catch (e) {
    return event.respondWith(new Response('Error thrown ' + e.message));
  }
});

async function handleRequest(request) {
  const algoliaUrl = new URL(request.url);
  algoliaUrl.host = `${ALGOLIA_APP_ID}-dsn.algolia.net`;

  const algoliaRequest = new Request(algoliaUrl, {
    body: request.body,
    headers: request.headers,
    method: request.method,
    redirect: request.redirect
  });

  let response = await fetch(algoliaRequest);

  // Reconstruct the Response object to make its headers mutable.
  response = new Response(response.body, response);

  response.headers.delete("cache-control");
  response.headers.set("Access-Control-ALlow-Origin", "*");
  response.headers.set("Access-Control-ALlow-Methods", "GET,HEAD,POST,OPTIONS");

  return response;
}

// post caching
async function handlePostRequest(event) {
  const request = event.request;
  const dupRequest = request.clone();
  // assumes JSON body
  const body = await dupRequest.json();

  // Hash the request body to use it as a part of the cache key
  const hash = await sha256(JSON.stringify(body));
  const cacheUrl = new URL(request.url);

  // Store the URL in cache by prepending the body's hash
  cacheUrl.pathname = '/posts' + cacheUrl.pathname + hash;

  // Convert to a GET to be able to cache
  const cacheKey = new Request(cacheUrl.toString(), {
    headers: request.headers,
    method: 'GET',
  });

  const cache = caches.default;

  // Find the cache key in the cache
  let response = await cache.match(cacheKey);

  // if not in cache, fetch response to POST request from origin + cache it
  if (!response) {
    response = await handleRequest(request);

    event.waitUntil(cache.put(cacheKey, response.clone()));
  }

  return response;
}

async function sha256(message) {
  // encode as UTF-8
  const msgBuffer = new TextEncoder().encode(message);

  // hash the message
  const hashBuffer = await crypto.subtle.digest('SHA-256', msgBuffer);

  // convert bytes to hex string
  return [...new Uint8Array(hashBuffer)].map(b => b.toString(16).padStart(2, '0')).join('');
}

Hey @etdev

I was writing something similar and came across your gist. In my case, it processes the request, but I'm still getting CF-Cache-Status: DYNAMIC and showing hits in the Algolia API logs repeated requests. Did you have to do anything else to get the cached response to return ?

Thanks!

Actually looks like it's working. I must not have been patient enough with the rollout of the worker. Thanks for putting this together and sharing!

Do you know how can I configure algoliasearch.js to use the proxy?

Hi everyone! 👋
If you're looking for a slightly more expanded version of this setup, I've put together a full repository based on a similar concept here: MarcinKilarski/algolia-caching-proxy-via-cloudflare-worker
It includes a complete Cloudflare Worker project structure, built-in security features (like CORS and domain whitelisting), and a detailed README with step-by-step instructions on how to set it up (including how to configure the frontend Algolia client to use the proxy).
Huge thanks to @etdev for the original gist and inspiration! Feel free to check out the repo if it helps with your use case.