# ServerRedis

**Kind:** Class

**Source:** [`packages/microservices/server/server-redis.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/server/server-redis.ts#L30)

**Part of:** [Microservices](subsystem-packages-microservices)

`ServerRedis` is the Redis transport server implementation for NestJS microservices. It creates Redis publisher/subscriber clients, subscribes to message patterns, dispatches incoming requests to registered handlers, and publishes responses or events back through Redis.

**Extends:** `Server`

## Methods

| Method | Signature | Returns |
|---|---|---|
| `listen` | `listen(callback: (err?: unknown, ...optionalParams: unknown[]) => void)` | `void` |
| `start` | `start(callback: () => void)` | `void` |
| `bindEvents` | `bindEvents(subClient: Redis, pubClient: Redis)` | `void` |
| `close` | `close()` | `void` |
| `createRedisClient` | `createRedisClient()` | `Redis` |
| `getMessageHandler` | `getMessageHandler(pub: Redis)` | `void` |
| `handleMessage` | `handleMessage(channel: string, buffer: string, pub: Redis, pattern: string)` | `void` |
| `getPublisher` | `getPublisher(pub: Redis, pattern: any, id: string, ctx: RedisContext)` | `void` |
| `parseMessage` | `parseMessage(content: any)` | `Record<string, any>` |
| `getRequestPattern` | `getRequestPattern(pattern: string)` | `string` |
| `getReplyPattern` | `getReplyPattern(pattern: string)` | `string` |
| `registerErrorListener` | `registerErrorListener(client: any)` | `void` |
| `registerReconnectListener` | `registerReconnectListener(client: { on: (event: string, fn: () => void) => void; })` | `void` |
| `registerReadyListener` | `registerReadyListener(client: { on: (event: string, fn: () => void) => void; })` | `void` |
| `registerEndListener` | `registerEndListener(client: { on: (event: string, fn: () => void) => void; })` | `void` |
| `getClientOptions` | `getClientOptions()` | `Partial<RedisOptions['options']>` |
| `createRetryStrategy` | `createRetryStrategy(times: number)` | `undefined | number | void` |
| `unwrap` | `unwrap()` | `T` |
| `on` | `on(event: EventKey, callback: EventCallback)` | `void` |

## Properties

| Property | Type |
|---|---|
| `transportId` | `TransportId` |
| `subClient` | `Redis` |
| `pubClient` | `Redis` |
| `isManuallyClosed` | `any` |
| `wasInitialConnectionSuccessful` | `any` |
| `pendingEventListeners` | `Array<{ event: keyof RedisEvents; callback: RedisEvents[keyof RedisEvents]; }>` |

## Where it refuses work

- `ServerRedis` stops the work with `Error` when `!this.pubClient || !this.subClient` — “Not initialized. Please call the "listen"/"startAllMicroservices" method before accessing…”.
- `ServerRedis` stops the work with an early return when `this.isManuallyClosed`, in 3 places.
- `ServerRedis` stops the work with an early return when `isUndefined((packet as IncomingRequest).id)`.

## When something fails

- `ServerRedis` handles failure in 2 places: it logs it and continues in 1, and turns it into a return value in 1.

## Diagram

```mermaid
graph LR
  Client[Redis Microservice Client] -->|Publish request/event| Redis[(Redis)]
  Redis -->|Subscribed channel| ServerRedis[ServerRedis]
  ServerRedis -->|Parse message| Handler[Registered Message Handler]
  Handler -->|Response| ServerRedis
  ServerRedis -->|Publish response| Redis
  Redis --> Client
```

## AI Coding Instructions

- Register message handlers with `addHandler()` before calling `listen()` so Redis subscriptions can route incoming patterns correctly.
- Keep request patterns stable and serializable; `getRequestPattern()` uses the pattern to determine the Redis subscription channel.
- Ensure Redis connection options match the deployed Redis instance, including authentication, TLS, retry behavior, and database selection where required.
- Always call `close()` during application shutdown to disconnect both publisher and subscriber Redis clients cleanly.
- Avoid placing long-running synchronous work in handlers; Redis message processing should delegate expensive work to asynchronous services or workers.

## Relationships

- IMPORTS → `isUndefined`