fix(redis): handle BullMQ connection error events to prevent worker crash on Redis loss

[saidai-bhuvanesh]

Summary

Fixes #1291

When Redis experiences a transient failover / socket disconnect, the BullMQ worker process crashes with an unhandled error event (surfaced as UnhandledPromiseRejectionError), halting all background blockchain transaction processing:

[INFO] [BlockchainWorker]: Worker initialized listening on queue 'blockchain-tx'
ERROR [ioredis]: Connection to 127.0.0.1:6379 failed - connect ECONNREFUSED
node:events:497
      throw er; // Unhandled 'error' event
Error: Connection is closed.
    at Redis.sendCommand (.../ioredis/built/redis/index.js:636:24)
    at Worker.retry (.../bullmq/dist/cjs/classes/worker.js:154:18)
Emitted 'error' event at:
    at Redis.emit (.../ioredis/built/redis/index.js:342:14)

Root cause

createQueueConnection() (backend/config/redis.js) returns a raw new Redis({...}) with no 'error' listener attached. BullMQ does not attach one to the user-provided connection either. In Node, an EventEmitter that emits 'error' with no listener throws and crashes the process. During a Redis drop, BullMQ's internal Worker.retry triggers an 'error' emission on the ioredis client → no listener → crash.

Note: getRedisConnection() (the shared app connection) already attaches an 'error' handler — only the BullMQ-specific createQueueConnection() (used by the Worker, Queue, and QueueEvents) was missing it.

Fix

Attach 'error' / 'close' / 'reconnecting' listeners to each BullMQ connection created by createQueueConnection(). The 'error' listener logs the failure instead of crashing the process, and ioredis then recovers via the existing retryStrategy / reconnectOnError with backoff.

function createQueueConnection() {
- return new Redis({
-   ...connectionOptions,
-   maxRetriesPerRequest: null,
- });
+ const connection = new Redis({
+   ...connectionOptions,
+   maxRetriesPerRequest: null,
+ });
+ connection.on("error", (err) => {
+   logger.error("❌ BullMQ Redis connection error", { error: err.message });
+ });
+ connection.on("close", () => { logger.warn("⚠️ BullMQ Redis connection closed"); });
+ connection.on("reconnecting", (delay) => { logger.warn(`🔄 BullMQ Redis reconnecting in ${delay}ms...`); });
+ return connection;
}

This covers the Worker, Queue, and QueueEvents connections (all built via createQueueConnection()).

Behavior

Event	Before	After
Redis drop / failover	process crash (UnhandledPromiseRejectionError)	logged + ioredis reconnects with backoff

Files

• backend/config/redis.js

---

This PR was created by an AI agent (OpenHands) on behalf of @saidai-bhuvanesh.

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