[#3127] Fix for Redis Sentinel client doesn't reconnect after connection failure

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

@@ -5,7 +5,7 @@ import { RESP_TYPES } from '../RESP/decoder';
 import { WatchError } from "../errors";
 import { RedisSentinelConfig, SentinelFramework } from "./test-util";
 import { RedisSentinelEvent, RedisSentinelType, RedisSentinelClientType, RedisNode } from "./types";
-import RedisSentinel from "./index";
+import RedisSentinel, { areSentinelListsEqual } from "./index";
 import { RedisModules, RedisFunctions, RedisScripts, RespVersions, TypeMapping, NumberReply } from '../RESP/types';
 import { promisify } from 'node:util';
 import { exec } from 'node:child_process';
@@ -30,6 +30,72 @@ describe('RedisSentinel', () => {
     assert.equal((sentinel as any).HOTKEYS_RESET, undefined);
   });
 
+  describe('areSentinelListsEqual', () => {
+    it('should return true for identical lists', () => {
+      const a = [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26380 }];
+      const b = [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26380 }];
+      assert.equal(areSentinelListsEqual(a, b), true);
+    });
+
+    it('should return true for empty lists', () => {
+      assert.equal(areSentinelListsEqual([], []), true);
+    });
+
+    it('should return false for different lengths', () => {
+      const a = [{ host: '127.0.0.1', port: 26379 }];
+      const b = [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26380 }];
+      assert.equal(areSentinelListsEqual(a, b), false);
+    });
+
+    it('should return false when hosts differ', () => {
+      const a = [{ host: '127.0.0.1', port: 26379 }];
+      const b = [{ host: '10.0.0.1', port: 26379 }];
+      assert.equal(areSentinelListsEqual(a, b), false);
+    });
+
+    it('should return false when ports differ', () => {
+      const a = [{ host: '127.0.0.1', port: 26379 }];
+      const b = [{ host: '127.0.0.1', port: 26380 }];
+      assert.equal(areSentinelListsEqual(a, b), false);
+    });
+
+    it('should return false when order differs (same elements)', () => {
+      const a = [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26380 }];
+      const b = [{ host: '127.0.0.1', port: 26380 }, { host: '127.0.0.1', port: 26379 }];
+      assert.equal(areSentinelListsEqual(a, b), false);
+    });
+
+    it('should detect change when same length but different content (regression: was only checking length)', () => {
+      const a = [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26380 }];
+      const b = [{ host: '127.0.0.1', port: 26379 }, { host: '127.0.0.1', port: 26381 }];
+      assert.equal(areSentinelListsEqual(a, b), false);
+    });
+  });
+
+  describe('sentinel root nodes preservation on failure', () => {
+    it('should preserve all sentinel root nodes after create (sentinels are not removed from config)', () => {
+      const sentinelRootNodes = [
+        { host: '127.0.0.1', port: 26379 },
+        { host: '127.0.0.1', port: 26380 },
+        { host: '127.0.0.1', port: 26381 }
+      ];
+
+      const sentinel = RedisSentinel.create({
+        name: 'mymaster',
+        sentinelRootNodes
+      });
+
+      // Verify all sentinel root nodes are preserved in the config
+      // (regression: #handleSentinelFailure used to splice nodes out of sentinelRootNodes)
+      assert.equal(sentinelRootNodes.length, 3, 'Original sentinelRootNodes array should not be modified');
+      assert.deepEqual(sentinelRootNodes, [
+        { host: '127.0.0.1', port: 26379 },
+        { host: '127.0.0.1', port: 26380 },
+        { host: '127.0.0.1', port: 26381 }
+      ]);
+    });
+  });
+
   describe('initialization', () => {
     describe('clientSideCache validation', () => {
       const clientSideCacheConfig = { ttl: 0, maxEntries: 0 };

packages/client/lib/sentinel/index.ts

@@ -18,6 +18,11 @@ import { TcpNetConnectOpts } from 'node:net';
 import { RedisTcpSocketOptions } from '../client/socket';
 import { BasicPooledClientSideCache, PooledClientSideCacheProvider } from '../client/cache';
 
+export function areSentinelListsEqual(a: ReadonlyArray<RedisNode>, b: ReadonlyArray<RedisNode>): boolean {
+  if (a.length !== b.length) return false;
+  return a.every((nodeA, i) => nodeA.host === b[i].host && nodeA.port === b[i].port);
+}
+
 interface ClientInfo {
   id: number;
 }
@@ -931,13 +936,7 @@ class RedisSentinelInternal<
     }
   }
 
-  #handleSentinelFailure(node: RedisNode) {
-    const found = this.#sentinelRootNodes.findIndex(
-        (rootNode) => rootNode.host === node.host && rootNode.port === node.port
-    );
-    if (found !== -1) {
-        this.#sentinelRootNodes.splice(found, 1);
-    }
+  #handleSentinelFailure(_node: RedisNode) {
     this.#reset();
   }
 
@@ -1347,7 +1346,7 @@ class RedisSentinelInternal<
       }
     }
 
-    if (analyzed.sentinelList.length != this.#sentinelRootNodes.length) {
+    if (!areSentinelListsEqual(analyzed.sentinelList, this.#sentinelRootNodes)) {
       this.#sentinelRootNodes = analyzed.sentinelList;
       const event: RedisSentinelEvent = {
         type: "SENTINE_LIST_CHANGE",