Which message pattern does the Pub/Sub library expose for effective routing

[kylehouston]

When using the NestJS hybrid approach what transport do we add to the @MessagePattern to ensure the events get routed to the correct callback?

export declare const MessagePattern: <T = string | PatternMetadata>(metadata?: T, transport?: Transport) => MethodDecorator;

@MessagePattern('test-topic', ???)
  async handlePubSubMessage(payload: any) {
    console.log(`Pub/Sub ----> ${JSON.stringify(payload)} created`);
  }

[kylehouston]

Looks like GCPPubSubServer Class needs to expose a transportId similar to https://github.com/nestjs/nest/blob/master/packages/microservices/server/server-redis.ts#L24

[ccoeurderoy]

Hey @kylehouston, that is a good question! And yes you are right, we should add the transportId property to this class. However, according to the CustomTransportStrategy interface, it expects a value from the Transport enum 😕 (even if we can hack this and disable typescript in this particular case, but I want to avoid this 😅)

It might be interesting to ask the question to the Nest Discord channel in order to know how we could handle hybrid applications with a custom microservice.

[kylehouston]

Thanks @ccoeurderoy - yeah the CustomTransportStrategy expecting the Transport enum was the bit that has me concerned. Out of interest, how would you hack this?

I'll reach out in the Discord for sure and see where things go!

[ccoeurderoy]

Out of interest, how would you hack this?

I could disable the TS check with a dirty // @ts-ignore since there is a condition on transportId here:

  /**
   * Transport ID required to bind transport when using hybrid applications
   * ⚠️ Custom number but could have conflict if Nest creates a new transport with this number
   */
  // @ts-ignore
  public readonly transportId: number = 10000;

But I don't like that honestly 😅 It also requires the MessagePattern decorator to ignore the TS build

[ccoeurderoy]

I'll keep this issue open until Nest provides a clean answer

[kylehouston]

Thanks @ccoeurderoy, looking again at the MessagePattern, there's a param for metadata - is there anything in the pub/sub library options I could use?

export declare const MessagePattern: <T = string | PatternMetadata>(metadata?: T, transport?: Transport) => MethodDecorator;

Logged a message in the support channel, hopefully someone will come back with a nice way to make this work :)

[ccoeurderoy]

is there anything in the pub/sub library options I could use?

Well, honestly I don't know since this signature has never been mentioned in the Nest documentation (sorry for the late answer)

By the way, did you get an answer from Discord?

[kylehouston]

No worries @ccoeurderoy - no reply in discord :/ I'll try following up, doesn't make sense that a custom strategy transport id should be a list of known nestjs enums

[ccoeurderoy]

Hey @kylehouston, I may be wrong, but it seems to be available since v8.3.0 (see this pull request) 🥳