Server

Kind: Class

Source: packages/microservices/server/server.ts

Part of: Microservices

Server is the base class for microservice transport servers. It manages message-handler registration and lookup, transport identification, and processing lifecycle hooks while allowing concrete transport implementations to provide connection, listening, shutdown, and native-client behavior.

Methods

Properties

Where it refuses work

• Server stops the work with an early return when !handler.
• Server stops the work with an early return when resultOrDeferred instanceof Promise.
• Server stops the work with an early return when isObservable(resultOrDeferred).

When something fails

• Server handles failure in 1 place: it logs it and continues in all 1.

Diagram

mermaid
graph LR
  Client[Microservice Client] --> Transport[Concrete Server Transport]
  Transport --> Server[Server Base Class]
  Server --> Handlers[Message Handler Map]
  Server --> StartHook[Processing Start Hook]
  Server --> EndHook[Processing End Hook]
  Handlers --> Handler[Message Handler]
  Handler --> Response[Response or Event Processing]

Usage

ts
import { Server } from '@nestjs/microservices';

class CustomServer extends Server {
  async listen(callback: () => void) {
    // Connect to the underlying transport here.
    callback();
  }

  async close() {
    // Close transport connections and release resources.
  }

  unwrap<T>() {
    // Return the underlying transport client/server instance.
    return {} as T;
  }
}

const server = new CustomServer();

server.setTransportId('custom-transport');

server.setOnProcessingStartHook(() => {
  console.log('Started processing message');
});

server.setOnProcessingEndHook(() => {
  console.log('Finished processing message');
});

server.addHandler('users.find', async (payload) => {
  return { id: payload.id, name: 'Ada Lovelace' };
});

await server.listen(() => {
  console.log('Custom microservice server is listening');
});

const handler = server.getHandlerByPattern('users.find');

if (handler) {
  const result = await handler({ id: 'user-1' });
  console.log(result);
}

await server.close();

AI Coding Instructions

• Extend Server when implementing a new transport; provide transport-specific listen(), close(), and unwrap() implementations.
• Register request and event handlers through addHandler() rather than mutating the handler map returned by getHandlers().
• Use the same normalized message pattern when registering handlers and retrieving them with getHandlerByPattern().
• Set a transport ID with setTransportId() when the transport must be identified by framework integrations or diagnostics.
• Keep processing hooks lightweight; use setOnProcessingStartHook() and setOnProcessingEndHook() for instrumentation, tracing, or metrics rather than business logic.