feat: add cluster/node events (#1855) (#3083)

* add cluster/node events
* add test for cluster events positive branch
* add cluster events docs section

fixes: #1855

---------

Co-authored-by: Nikolay Karadzhov <nkaradzhov89@gmail.com>

docs/clustering.md

@@ -120,6 +120,24 @@ createCluster({
 
 > This is a common problem when using ElastiCache. See [Accessing ElastiCache from outside AWS](https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/accessing-elasticache.html) for more information on that.
 
+### Events
+
+The Node Redis Cluster class extends Node.js’s EventEmitter and emits the following events:
+
+| Name                    | When                                                                               | Listener arguments                                        |
+| ----------------------- | ---------------------------------------------------------------------------------- | --------------------------------------------------------- |
+| `connect`               | The cluster has successfully connected and is ready to us                          | _No arguments_                                            |
+| `disconnect`            | The cluster has disconnected                                                       | _No arguments_                                            |
+| `error`                 | The cluster has errored                                                            | `(error: Error)`                                          |
+| `node-ready`            | A cluster node is ready to establish a connection                                  | `(node: { host: string, port: number })`                  |
+| `node-connect`          | A cluster node has connected                                                       | `(node: { host: string, port: number })`                  |
+| `node-reconnecting`     | A cluster node is attempting to reconnect after an error                           | `(node: { host: string, port: number })`                  |
+| `node-disconnect`       | A cluster node has disconnected                                                    | `(node: { host: string, port: number })`                  |
+| `node-error`            | A cluster node has has errored (usually during TCP connection)                     | `(error: Error, node: { host: string, port: number })`    |
+
+> :warning: You **MUST** listen to `error` events. If a cluster doesn't have at least one `error` listener registered and
+> an `error` occurs, that error will be thrown and the Node.js process will exit. See the [ > `EventEmitter` docs](https://nodejs.org/api/events.html#events_error_events) for more details.
+
 ## Command Routing
 
 ### Commands that operate on Redis Keys

packages/client/lib/cluster/cluster-slots.ts

@@ -153,6 +153,7 @@ export default class RedisClusterSlots<
     this.#isOpen = true;
     try {
       await this.#discoverWithRootNodes();
+      this.#emit('connect');
     } catch (err) {
       this.#isOpen = false;
       throw err;
@@ -333,17 +334,26 @@ export default class RedisClusterSlots<
   }
 
   #createClient(node: ShardNode<M, F, S, RESP, TYPE_MAPPING>, readonly = node.readonly) {
+    const socket =
+      this.#getNodeAddress(node.address) ??
+      { host: node.host, port: node.port, };
+    const client = Object.freeze({
+      host: socket.host,
+      port: socket.port,
+    });
+    const emit = this.#emit;
     return this.#clientFactory(
       this.#clientOptionsDefaults({
         clientSideCache: this.clientSideCache,
         RESP: this.#options.RESP,
-        socket: this.#getNodeAddress(node.address) ?? {
+        socket,
-          host: node.host,
+        readonly,
-          port: node.port
+      }))
-        },
+      .on('error', error => emit('node-error', error, client))
-        readonly
+      .on('reconnecting', () => emit('node-reconnecting', client))
-      })
+      .once('ready', () => emit('node-ready', client))
-    ).on('error', err => console.error(err));
+      .once('connect', () => emit('node-connect', client))
+      .once('end', () => emit('node-disconnect', client));
   }
 
   #createNodeClient(node: ShardNode<M, F, S, RESP, TYPE_MAPPING>, readonly?: boolean) {
@@ -406,6 +416,7 @@ export default class RedisClusterSlots<
 
     this.#resetSlots();
     this.nodeByAddress.clear();
+    this.#emit('disconnect');
   }
 
   *#clients() {
@@ -443,6 +454,7 @@ export default class RedisClusterSlots<
     this.nodeByAddress.clear();
 
     await Promise.allSettled(promises);
+    this.#emit('disconnect');
   }
 
   getClient(

packages/client/lib/cluster/index.spec.ts

@@ -339,4 +339,43 @@ describe('Cluster', () => {
       minimumDockerVersion: [7]
     });
   });
+
+  describe('clusterEvents', () => {
+    testUtils.testWithCluster('should fire events', async (cluster) => {
+      const log: string[] = [];
+
+      cluster
+        .on('connect', () => log.push('connect'))
+        .on('disconnect', () => log.push('disconnect'))
+        .on('error', () => log.push('error'))
+        .on('node-error', () => log.push('node-error'))
+        .on('node-reconnecting', () => log.push('node-reconnecting'))
+        .on('node-ready', () => log.push('node-ready'))
+        .on('node-connect', () => log.push('node-connect'))
+        .on('node-disconnect', () => log.push('node-disconnect'))
+
+      await cluster.connect();
+      cluster.destroy();
+
+      assert.deepEqual(log, [
+        'node-connect',
+        'node-connect',
+        'node-ready',
+        'node-ready',
+        'connect',
+        'node-disconnect',
+        'node-disconnect',
+        'disconnect',
+      ]);
+    }, {
+      ...GLOBAL.CLUSTERS.OPEN,
+      disableClusterSetup: true,
+      numberOfMasters: 2,
+      numberOfReplicas: 1,
+      clusterConfiguration: {
+        minimizeConnections: false
+      }
+    });
+  });
+
 });

packages/test-utils/lib/index.ts

@@ -116,6 +116,7 @@ interface ClusterTestOptions<
   clusterConfiguration?: Partial<RedisClusterOptions<M, F, S, RESP, TYPE_MAPPING/*, POLICIES*/>>;
   numberOfMasters?: number;
   numberOfReplicas?: number;
+  disableClusterSetup?: boolean;
 }
 
 interface AllTestOptions<
@@ -554,10 +555,14 @@ export default class TestUtils {
               port
             }
           })),
-          minimizeConnections: true,
+          minimizeConnections: options.clusterConfiguration?.minimizeConnections ?? true,
           ...options.clusterConfiguration
         });
 
+      if(options.disableClusterSetup) {
+        return fn(cluster);
+      }
+
       await cluster.connect();
 
       try {