fix: disable retries on cluster subscriber connections. See discussio…

…n in #1589

lib/cluster/ClusterSubscriber.ts

@@ -15,6 +15,14 @@ export default class ClusterSubscriber {
     private connectionPool: ConnectionPool,
     private emitter: EventEmitter
   ) {
+    // If the current node we're using as the subscriber disappears
+    // from the node pool for some reason, we will select a new one
+    // to connect to.
+    // Note that this event is only triggered if the connection to
+    // the node has been used; cluster subscriptions are setup with
+    // lazyConnect = true. It's possible for the subscriber node to
+    // disappear without this method being called!
+    // See https://github.com/luin/ioredis/pull/1589
     this.connectionPool.on("-node", (_, key: string) => {
       if (!this.started || !this.subscriber) {
         return;
@@ -97,6 +105,10 @@ export default class ClusterSubscriber {
       connectionName: getConnectionName("subscriber", options.connectionName),
       lazyConnect: true,
       tls: options.tls,
+      // Don't try to reconnect the subscriber connection. If the connection fails
+      // we will get an end event (handled below), at which point we'll pick a new
+      // node from the pool and try to connect to that as the subscriber connection.
+      retryStrategy: null
     });
 
     // Ignore the errors since they're handled in the connection pool.
@@ -105,14 +117,19 @@ export default class ClusterSubscriber {
     // The node we lost connection to may not come back up in a
     // reasonable amount of time (e.g. a slave that's taken down
     // for maintainence), we could potentially miss many published
-    // messages so we should reconnect as quickly as possible.
+    // messages so we should reconnect as quickly as possible, to
+    // a different node if needed.
     const currentSub = this.subscriber;
-    this.subscriber.once("close", () => {
+    this.subscriber.once("end", () => {
+        if (!this.started) {
+          debug("subscriber has disconnected, but ClusterSubscriber is not started, so not reconnecting.");
+          return;
+        }
       // If the subscriber closes whilst it's still the active connection,
       // we might as well try to connecting to a new node if possible to
       // minimise the number of missed publishes.
-      if (this.started && currentSub === this.subscriber) {
-        debug("current subscriber closed, selecting a new node.");
+      if (currentSub === this.subscriber) {
+          debug("subscriber has disconnected, selecting a new one...");
         this.selectSubscriber();
       }
     });