feat(cache): implement read and write handlers for Redis

Currently, the redis cache handler is reading and writing from the primary endpoint which is causing throttling from the primary instance. Instead, reads should come from read-only replicas and writes go to the primary. This changes the caching pattern to eventual consistency, but this is acceptable for the marketing sites.

- Added separate read and write handlers for Redis caching.
- Updated constructor to initialize handlers based on environment variables.
- Modified methods to use new handlers for cache operations.

Author: stephenliang

apps/marketing/cache-handler.mjs

@@ -5,7 +5,8 @@ import {RedisStringsHandler} from '@trieb.work/nextjs-turbo-redis-cache';
  */
 class RedisCacheHandler {
   static #instance = null;
-  cachedHandler;
+  writeCachedHandler;
+  readCachedHandler;
 
   constructor() {
     if (RedisCacheHandler.#instance) {
@@ -14,27 +15,28 @@ class RedisCacheHandler {
     RedisCacheHandler.#instance = this;
 
     const isRedisCacheEnabled =
-      process.env.REDIS_URL && process.env.NODE_ENV === 'production';
+      process.env.REDIS_READ_URL &&
+      process.env.REDIS_WRITE_URL &&
+      process.env.NODE_ENV === 'production';
 
     if (isRedisCacheEnabled) {
       console.debug(`Using Redis cache`);
-      this.cachedHandler = new RedisStringsHandler({
-        database: 0,
-        keyPrefix: 'marketing-sites::',
-        sharedTagsKey: '__sharedTags__',
-        // Enable TLS if the REDIS_URL starts with 'rediss://'
-        ...(process.env.REDIS_URL.startsWith('rediss://')
-          ? {
-              socketOptions: {
-                tls: true,
-              },
-            }
-          : undefined),
-      });
+      this.writeCachedHandler = this.createCacheHandler(
+        process.env.REDIS_WRITE_URL,
+      );
+      this.readCachedHandler = this.createCacheHandler(
+        process.env.REDIS_READ_URL,
+      );
     } else {
       console.warn('Redis cache disabled, using no-op handler');
       // Create a no-op handler if Redis is disabled
-      this.cachedHandler = {
+      this.readCachedHandler = {
+        get: async () => null,
+        set: async () => {},
+        revalidateTag: async () => {},
+        resetRequestCache: async () => {},
+      };
+      this.writeCachedHandler = {
         get: async () => null,
         set: async () => {},
         revalidateTag: async () => {},
@@ -43,36 +45,59 @@ class RedisCacheHandler {
     }
   }
 
+  createCacheHandler(endpoint) {
+    return new RedisStringsHandler({
+      database: 0,
+      keyPrefix: 'marketing-sites::',
+      sharedTagsKey: '__sharedTags__',
+      redisUrl: endpoint,
+      // Enable TLS if the endpoint starts with 'rediss://'
+      ...(endpoint.startsWith('rediss://')
+        ? {
+            socketOptions: {
+              tls: true,
+            },
+          }
+        : undefined),
+    });
+  }
+
   /**
    * @param {...Parameters<RedisStringsHandler['get']>} args
    * @returns {ReturnType<RedisStringsHandler['get']>}
    */
   get(...args) {
-    return this.cachedHandler.get(...args);
+    return this.readCachedHandler.get(...args);
   }
 
   /**
    * @param {...Parameters<RedisStringsHandler['set']>} args
    * @returns {ReturnType<RedisStringsHandler['set']>}
    */
   set(...args) {
-    return this.cachedHandler.set(...args);
+    return this.writeCachedHandler.set(...args);
   }
 
   /**
    * @param {...Parameters<RedisStringsHandler['revalidateTag']>} args
    * @returns {ReturnType<RedisStringsHandler['revalidateTag']>}
    */
   revalidateTag(...args) {
-    return this.cachedHandler.revalidateTag(...args);
+    return Promise.all([
+      this.readCachedHandler.revalidateTag(...args),
+      this.writeCachedHandler.revalidateTag(...args),
+    ]);
   }
 
   /**
    * @param {...Parameters<RedisStringsHandler['resetRequestCache']>} args
    * @returns {ReturnType<RedisStringsHandler['resetRequestCache']>}
    */
   resetRequestCache(...args) {
-    return this.cachedHandler.resetRequestCache(...args);
+    return Promise.all([
+      this.readCachedHandler.resetRequestCache(...args),
+      this.writeCachedHandler.resetRequestCache(...args),
+    ]);
   }
 }
 

apps/marketing/cicd/3-app/template.yml.erb

@@ -518,8 +518,10 @@ Resources:
               Value: !Ref EnvironmentType
             - Name: NEXT_PUBLIC_INSTRUMENTATION_ENABLED
               Value: "true"
-            - Name: REDIS_URL
+            - Name: REDIS_WRITE_URL
               Value: !Sub "rediss://${RedisCluster.PrimaryEndPoint.Address}:6379"
+            - Name: REDIS_READ_URL
+              Value: !Sub "rediss://${RedisCluster.ReaderEndPoint.Address}:6379"
             # Do not verify that keyspace is available, as it is created by the RedisParameterGroup
             - Name: SKIP_KEYSPACE_CONFIG_CHECK
               Value: "true"