Speeding Up Your Website Using Fastify and Redis Cache

const isCacheableRequest = (request: FastifyRequest): boolean => { // Do not attempt to use cache for authenticated visitors. if (request.visitor?.userAccount) { return false; } if (request.method !== 'GET') { return false; } // We only want to cache responses under /supplements/. if (!request.url.includes('/supplements/')) { return false; } // We provide a mechanism to bypass the cache. // This is necessary for implementing the "Serve Stale Content While Revalidating" feature. if (request.headers['cache-control'] === 'no-cache') { return false; } return true; }; const isCacheableResponse = (reply: FastifyReply): boolean => { if (reply.statusCode !== 200) { return false; } // We don't want to cache responses that are served from the cache. if (reply.getHeader('x-pillser-cache') === 'HIT') { return false; } // We only want to cache responses that are HTML. if (!reply.getHeader('content-type')?.toString().includes('text/html')) { return false; } return true; }; const generateRequestCacheKey = (request: FastifyRequest): string => { // We need to namespace the cache key to allow an easy purging of all the cache entries. return 'request:' + generateHash({ algorithm: 'sha256', buffer: stringifyJson({ method: request.method, url: request.url, // This is used to cache viewport specific responses. viewportWidth: request.viewportWidth, }), encoding: 'hex', }); }; type CachedResponse = { body: string; headers: Record; statusCode: number; }; const refreshRequestCache = async (request: FastifyRequest) => { await got({ headers: { 'cache-control': 'no-cache', 'sec-ch-viewport-width': String(request.viewportWidth), 'user-agent': request.headers['user-agent'], }, method: 'GET', url: pathToAbsoluteUrl(request.originalUrl), }); }; app.addHook('onRequest', async (request, reply) => { if (!isCacheableRequest(request)) { return; } const cachedResponse = await redis.get(generateRequestCacheKey(request)); if (!cachedResponse) { return; } reply.header('x-pillser-cache', 'HIT'); const response: CachedResponse = parseJson(cachedResponse); reply.status(response.statusCode); reply.headers(response.headers); reply.send(response.body); reply.hijack(); setImmediate(() => { // After the response is sent, we send a request to refresh the cache in the background. // This effectively serves stale content while revalidating. // Therefore, this cache does not reduce the number of requests to the origin; // The goal is to reduce the response time for the user. refreshRequestCache(request); }); }); const readableToString = (readable: Readable): Promise => { const chunks: Uint8Array[] = []; return new Promise((resolve, reject) => { readable.on('data', (chunk) => chunks.push(Buffer.from(chunk))); readable.on('error', (err) => reject(err)); readable.on('end', () => resolve(Buffer.concat(chunks).toString('utf8'))); }); }; app.addHook('onSend', async (request, reply, payload) => { if (reply.hasHeader('x-pillser-cache')) { return payload; } if (!isCacheableRequest(request) || !isCacheableResponse(reply) || !(payload instanceof Readable)) { // Indicate that the response is not cacheable. reply.header('x-pillser-cache', 'DYNAMIC'); return payload; } const content = await readableToString(payload); const headers = omit(reply.getHeaders(), [ 'content-length', 'set-cookie', 'x-pillser-cache', ]) as Record; reply.header('x-pillser-cache', 'MISS'); await redis.setex( generateRequestCacheKey(request), getDuration('1 day', 'seconds'), stringifyJson({ body: content, headers, statusCode: reply.statusCode, } satisfies CachedResponse), ); return content; });