chore(backend): Caching envvars

backend/.env.example

@@ -66,3 +66,10 @@ DWENGO_AUTH_TEACHER_JWKS_ENDPOINT=http://hostname/realms/teacher/protocol/openid
 # The address of the Loki instance, a log aggregation system.
 # If running your stack in docker, this should use the docker service name.
 #DWENGO_LOGGING_LOKI_HOST=http://localhost:3102
+
+# The hostname or IP address of the Redis cache.
+# If running your stack in docker, this should use the docker service name.
+#DWENGO_CACHE_HOST=localhost
+#DWENGO_CACHE_PORT=6379
+#DWENGO_CACHE_TTL=3600
+#DWENGO_CACHE_KEY_PREFIX=dwengo

backend/.env.production.example

@@ -35,3 +35,7 @@ DWENGO_AUTH_TEACHER_JWKS_ENDPOINT=http://idp:7080/idp/realms/teacher/protocol/op
 
 DWENGO_LOGGING_LEVEL=info
 DWENGO_LOGGING_LOKI_HOST=http://logging:3102
+
+DWENGO_CACHE_HOST=cache
+#DWENGO_CACHE_PORT=6379
+DWENGO_CACHE_TTL=604800

backend/.env.staging

@@ -1,4 +1,6 @@
 PORT=3000
+DWENGO_RUN_MODE=staging
+
 DWENGO_DB_HOST=db
 DWENGO_DB_PORT=5432
 DWENGO_DB_USERNAME=postgres
@@ -18,4 +20,8 @@ DWENGO_CORS_ALLOWED_ORIGINS=http://localhost/*,http://idp:7080,https://idp:7080
 
 # Logging and monitoring
 
-LOKI_HOST=http://logging:3102
+DWENGO_LOGGING_LEVEL=debug
+DWENGO_LOGGING_LOKI_HOST=http://logging:3102
+
+DWENGO_CACHE_HOST=caching
+DWENGO_CACHE_TTL=86400

backend/src/caching.ts

@@ -0,0 +1,42 @@
+import { createClient, RedisClientType } from 'redis';
+import { getLogger } from './logging/initalize.js';
+import { envVars, getEnvVar } from './util/envVars.js';
+
+export type CacheClient = RedisClientType;
+
+let redisClient: CacheClient;
+
+async function initializeClient(): Promise<CacheClient> {
+    if (redisClient !== undefined) {
+        return redisClient;
+    }
+
+    const redisHost = getEnvVar(envVars.CacheHost);
+    const redisPort = getEnvVar(envVars.CachePort);
+    const redisUrl = `redis://${redisHost}:${redisPort}`;
+
+    redisClient = createClient({
+        url: redisUrl
+    });
+
+    redisClient.on('error', (err) => getLogger().error('Redis error:', err));
+    await redisClient.connect();
+
+    return redisClient;
+}
+
+export async function getCacheClient(): Promise<CacheClient> {
+    redisClient ||= await initializeClient();
+    return redisClient;
+}
+
+export async function checkRedisHealth(): Promise<boolean> {
+    try {
+        await redisClient.set('health', 'ok');
+        const reply = await redisClient.get('health');
+        return reply === 'ok';
+    } catch (error) {
+        getLogger().error('Redis Health Check Failed:', error);
+        return false;
+    }
+}

backend/src/util/envVars.ts

@@ -5,6 +5,7 @@ const STUDENT_IDP_PREFIX = IDP_PREFIX + 'STUDENT_';
 const TEACHER_IDP_PREFIX = IDP_PREFIX + 'TEACHER_';
 const CORS_PREFIX = PREFIX + 'CORS_';
 const LOGGING_PREFIX = PREFIX + 'LOGGING_';
+const CACHE_PREFIX = PREFIX + 'CACHE_';
 
 interface EnvVar {
     key: string;
@@ -39,6 +40,11 @@ export const envVars: Record<string, EnvVar> = {
 
     LogLevel: { key: LOGGING_PREFIX + 'LEVEL', defaultValue: 'info' },
     LokiHost: { key: LOGGING_PREFIX + 'LOKI_HOST', defaultValue: 'http://localhost:3102' },
+
+    CacheHost: { key: CACHE_PREFIX + 'HOST', defaultValue: 'localhost' },
+    CachePort: { key: CACHE_PREFIX + 'PORT', defaultValue: 6379 },
+    CacheTTL: { key: CACHE_PREFIX + 'TTL', defaultValue: 60 * 60 * 24 }, // 24 hours
+    CacheKeyPrefix: { key: CACHE_PREFIX + 'KEY_PREFIX', defaultValue: 'dwengo' },
 } as const;
 
 /**