Implement TTL and use our own repository to cache requests (#83)

* Implement TTL and use our own repository to cache requests

* Remove unused import

apps/api/src/app/plugins/bffCache.ts

@@ -1,21 +1,23 @@
 import fp from 'fastify-plugin';
 import {
   CACHE_CONTROL_HEADER,
-  getCache,
   getCacheControlHeaderValue,
   parseCacheControlHeaderValue,
-  setCache,
 } from '../../utils/cache';
-import {
-  FastifyInstance,
-  FastifyPluginCallback,
-  FastifyReply,
-  FastifyRequest,
-} from 'fastify';
+import { FastifyPluginCallback, FastifyReply, FastifyRequest } from 'fastify';
 
 const HEADER_NAME = 'x-bff-cache';
-import { getCacheKey } from '@cowprotocol/repositories';
+import {
+  CacheRepository,
+  cacheRepositorySymbol,
+  getCacheKey,
+} from '@cowprotocol/repositories';
 import { Readable } from 'stream';
+import { apiContainer } from '../inversify.config';
+
+const cacheRepository: CacheRepository = apiContainer.get(
+  cacheRepositorySymbol
+);
 
 interface BffCacheOptions {
   ttl?: number;
@@ -38,16 +40,18 @@ export const bffCache: FastifyPluginCallback<BffCacheOptions> = (
     // Remove it so we can cache it properly
     request.headers['accept-encoding'] = undefined;
 
-    const cacheItem = await getCache(key, fastify).catch((e) => {
+    const [item, ttl] = await Promise.all([
+      cacheRepository.get(key),
+      cacheRepository.getTtl(key),
+    ]).catch((e) => {
       fastify.log.error(`Error getting key ${key} from cache`, e);
-      return undefined;
+      return [null, null];
     });
 
-    if (cacheItem) {
-      const { item, ttl } = cacheItem;
-      fastify.log.debug(`Found cached item "${item}" with TTL`, ttl);
+    if (item !== null && ttl !== null) {
+      fastify.log.debug(`Found cached item "${item}" with TTL ${ttl}`);
 
-      const ttlInSeconds = isNaN(ttl) ? undefined : Math.floor(ttl / 1000);
+      const ttlInSeconds = isNaN(ttl) ? undefined : ttl;
 
       if (ttlInSeconds !== undefined) {
         reply.header(
@@ -91,7 +95,7 @@ export const bffCache: FastifyPluginCallback<BffCacheOptions> = (
       if (content !== null) {
         // Cache (fire and forget)
         const key = getKey(req);
-        setCache(key, content, cacheTtl, fastify).catch((e) => {
+        cacheRepository.set(key, content, cacheTtl).catch((e) => {
           fastify.log.error(`Error setting key ${key} to cache`, e);
         });
         reply.header(

libs/repositories/src/CacheRepository/CacheRepository.ts

@@ -2,5 +2,6 @@ export const cacheRepositorySymbol = Symbol.for('CacheRepository');
 
 export interface CacheRepository {
   get(key: string): Promise<string | null>;
+  getTtl(key: string): Promise<number | null>;
   set(key: string, value: string, ttl: number): Promise<void>;
 }

libs/repositories/src/CacheRepository/CacheRepositoryMemory.ts

@@ -12,6 +12,16 @@ export class CacheRepositoryMemory implements CacheRepository {
     return value ?? null;
   }
 
+  async getTtl(key: string): Promise<number | null> {
+    const ttlEpoch = (await CacheRepositoryMemory.cache.getTtl(key)) || null;
+
+    if (ttlEpoch === null) {
+      return null;
+    }
+
+    return Math.floor((ttlEpoch - Date.now()) / 1000);
+  }
+
   async set(key: string, value: string, ttl: number): Promise<void> {
     await CacheRepositoryMemory.cache.set(key, value, ttl);
   }

libs/repositories/src/CacheRepository/CacheRepositoryRedis.ts

@@ -1,14 +1,25 @@
 import { injectable } from 'inversify';
 import { CacheRepository } from './CacheRepository';
+import { Redis } from 'ioredis';
 
 @injectable()
 export class CacheRepositoryRedis implements CacheRepository {
-  constructor(private redisClient: any) {}
+  constructor(private redisClient: Redis) {}
 
   async get(key: string): Promise<string | null> {
     return this.redisClient.get(key);
   }
 
+  async getTtl(key: string): Promise<number | null> {
+    const ttl = await this.redisClient.ttl(key);
+
+    if (ttl < 0) {
+      return null;
+    }
+
+    return ttl;
+  }
+
   async set(key: string, value: string, ttl: number): Promise<void> {
     await this.redisClient.set(key, value, 'EX', ttl);
   }