refactor(core): Flatten Redis pubsub class hierarchy (no-changelog) (#10616)

packages/cli/src/scaling/pubsub/subscriber.service.ts

@@ -0,0 +1,60 @@
+import type { Redis as SingleNodeClient, Cluster as MultiNodeClient } from 'ioredis';
+import { Service } from 'typedi';
+
+import config from '@/config';
+import { Logger } from '@/logger';
+import { RedisClientService } from '@/services/redis/redis-client.service';
+
+import type { ScalingPubSubChannel } from './pubsub.types';
+
+/**
+ * Responsible for subscribing to the pubsub channels used by scaling mode.
+ */
+@Service()
+export class Subscriber {
+	private readonly client: SingleNodeClient | MultiNodeClient;
+
+	// #region Lifecycle
+
+	constructor(
+		private readonly logger: Logger,
+		private readonly redisClientService: RedisClientService,
+	) {
+		// @TODO: Once this class is only ever initialized in scaling mode, throw in the next line instead.
+		if (config.getEnv('executions.mode') !== 'queue') return;
+
+		this.client = this.redisClientService.createClient({ type: 'subscriber(n8n)' });
+
+		this.client.on('error', (error) => this.logger.error(error.message));
+	}
+
+	getClient() {
+		return this.client;
+	}
+
+	// @TODO: Use `@OnShutdown()` decorator
+	shutdown() {
+		this.client.disconnect();
+	}
+
+	// #endregion
+
+	// #region Subscribing
+
+	async subscribe(channel: ScalingPubSubChannel) {
+		await this.client.subscribe(channel, (error) => {
+			if (error) {
+				this.logger.error('Failed to subscribe to channel', { channel, cause: error });
+				return;
+			}
+
+			this.logger.debug('Subscribed to channel', { channel });
+		});
+	}
+
+	addMessageHandler(handlerFn: (channel: string, msg: string) => void) {
+		this.client.on('message', handlerFn);
+	}
+
+	// #endregion
+}