init commit

src/pubsub/redis.js

@@ -0,0 +1,70 @@
+import { EventEmitter } from 'events';
+import { v4 as uuidv4 } from 'uuid';
+
+const LOGGER = require('@calzoneman/jsli')('redis-messagebus');
+
+class RedisMessageBus extends EventEmitter {
+    constructor(pubClient, subClient, channel) {
+        super();
+
+        this.pubClient = pubClient;
+        this.subClient = subClient;
+        this.channel = channel;
+        this.publisherID = uuidv4();
+
+        subClient.once('ready', this.subscribe.bind(this));
+    }
+
+    subscribe() {
+        this.subClient.subscribe(this.channel);
+        this.subClient.on('message', this.onMessage.bind(this));
+
+        LOGGER.info('Subscribed to Redis messages on channel %s', this.channel);
+    }
+
+    onMessage(channel, message) {
+        if (channel !== this.channel) {
+            LOGGER.warn('Ignoring message from mismatched channel "%s"', channel);
+            return;
+        }
+
+        try {
+            const { event, payload } = JSON.parse(message);
+
+            this._emit(event, payload);
+        } catch (error) {
+            if (error instanceof SyntaxError) {
+                LOGGER.error(
+                        'Malformed message received: %s (message: "%s")',
+                        message,
+                        error
+                );
+            } else {
+                LOGGER.error('Unexpected error decoding message: %s', error.stack);
+            }
+
+            return;
+        }
+    }
+
+    async emit(event, payload) {
+        try {
+            const message = JSON.stringify({
+                time: new Date(),
+                publisher: this.publisherID,
+                event,
+                payload
+            });
+
+            await this.pubClient.publish(this.channel, message);
+        } catch (error) {
+            LOGGER.error('Unable to send event %s: %s', event, error);
+        }
+    }
+}
+
+Object.assign(RedisMessageBus.prototype, {
+    _emit: EventEmitter.prototype.emit
+});
+
+export { RedisMessageBus };