refactor(socket): Add maintenance mode support and dynamic timeout handling

- Introduced `#inMaintenance` property and setter to track maintenance mode state in `RedisSocket`.
- Added `#maintenanceTimeout` and `setMaintenanceTimeout` method to dynamically adjust socket timeouts during maintenance.
- Enhanced timeout error handling to differentiate between regular timeouts (`SocketTimeoutError`) and maintenance-specific timeouts (`SocketTimeoutDuringMaintananceError`).

Author: nkaradzhov

packages/client/lib/client/socket.ts

@@ -1,7 +1,7 @@
 import { EventEmitter, once } from 'node:events';
 import net from 'node:net';
 import tls from 'node:tls';
-import { ConnectionTimeoutError, ClientClosedError, SocketClosedUnexpectedlyError, ReconnectStrategyError, SocketTimeoutError } from '../errors';
+import { ConnectionTimeoutError, ClientClosedError, SocketClosedUnexpectedlyError, ReconnectStrategyError, SocketTimeoutError, SocketTimeoutDuringMaintananceError } from '../errors';
 import { setTimeout } from 'node:timers/promises';
 import { RedisArgument } from '../RESP/types';
 
@@ -60,6 +60,8 @@ export default class RedisSocket extends EventEmitter {
   readonly #socketFactory;
   readonly #socketTimeout;
 
+  #maintenanceTimeout: number | undefined;
+
   #socket?: net.Socket | tls.TLSSocket;
 
   #isOpen = false;
@@ -82,6 +84,12 @@ export default class RedisSocket extends EventEmitter {
     return this.#socketEpoch;
   }
 
+  #inMaintenance = false;
+
+  set inMaintenance(value: boolean) {
+    this.#inMaintenance = value;
+  }
+
   constructor(initiator: RedisSocketInitiator, options?: RedisSocketOptions) {
     super();
 
@@ -238,6 +246,18 @@ export default class RedisSocket extends EventEmitter {
     } while (this.#isOpen && !this.#isReady);
   }
 
+  setMaintenanceTimeout(ms?: number) {
+    if (this.#maintenanceTimeout === ms) return;
+
+    this.#maintenanceTimeout = ms;
+
+    if(ms !== undefined) {
+      this.#socket?.setTimeout(ms);
+    } else {
+      this.#socket?.setTimeout(this.#socketTimeout ?? 0);
+    }
+  }
+
   async #createSocket(): Promise<net.Socket | tls.TLSSocket> {
     const socket = this.#socketFactory.create();
 
@@ -260,7 +280,10 @@ export default class RedisSocket extends EventEmitter {
 
     if (this.#socketTimeout) {
       socket.once('timeout', () => {
-        socket.destroy(new SocketTimeoutError(this.#socketTimeout!));
+        const error = this.#inMaintenance
+          ? new SocketTimeoutDuringMaintananceError(this.#socketTimeout!)
+          : new SocketTimeoutError(this.#socketTimeout!)
+        socket.destroy(error);
       });
       socket.setTimeout(this.#socketTimeout);
     }