fix(SENTINEL): actively failover detection under an option (#1363)

lib/connectors/SentinelConnector/index.ts

@@ -52,6 +52,7 @@ export interface ISentinelConnectionOptions extends ITcpConnectionOptions {
   natMap?: INatMap;
   updateSentinels?: boolean;
   sentinelMaxConnections?: number;
+  failoverDetector?: boolean;
 }
 
 export default class SentinelConnector extends AbstractConnector {
@@ -321,6 +322,9 @@ export default class SentinelConnector extends AbstractConnector {
   }
 
   private async initFailoverDetector(): Promise<void> {
+    if (!this.options.failoverDetector) {
+      return;
+    }
     // Move the current sentinel to the first position
     this.sentinelIterator.reset(true);
 

lib/redis/RedisOptions.ts

@@ -63,6 +63,7 @@ export const DEFAULT_REDIS_OPTIONS: IRedisOptions = {
   natMap: null,
   enableTLSForSentinelMode: false,
   updateSentinels: true,
+  failoverDetector: false,
   // Status
   username: null,
   password: null,

lib/redis/index.ts

@@ -98,6 +98,11 @@ const debug = Debug("redis");
  * @param {NatMap} [options.natMap=null] NAT map for sentinel connector.
  * @param {boolean} [options.updateSentinels=true] - Update the given `sentinels` list with new IP
  * addresses when communicating with existing sentinels.
+ * @param {boolean} [options.failoverDetector=false] - Detect failover actively by subscribing to the
+ * related channels. With this option disabled, ioredis is still able to detect failovers because Redis
+ * Sentinel will disconnect all clients whenever a failover happens, so ioredis will reconnect to the new
+ * master. This option is useful when you want to detect failover quicker, but it will create more TCP
+ * connections to Redis servers in order to subscribe to related channels.
 * @param {boolean} [options.enableAutoPipelining=false] - When enabled, all commands issued during an event loop
  * iteration are automatically wrapped in a pipeline and sent to the server at the same time.
  * This can dramatically improve performance.