Entire NestJS Module Revamp + Handling multiple connections

[EnriqCG]

Context of the revamp

Previous partial support for handling multiple AMQP connections involved using the same root AMQPModule and passing an array of connections.

nestjs-amqp/lib/amqp.module.ts

Line 22 in b97d1d4

static forRoot(options: AMQPModuleOptions | AMQPModuleOptions[]): DynamicModule {

amqplib connection objects were stored within the same module in a Map. When performing actions on a particular connection or channel, retrieval from the Map had to happen:

nestjs-amqp/lib/amqp.service.ts

Lines 15 to 22 in b97d1d4

	getChannel(connectionName?: string): ChannelWrapper {
	if (!connectionName) {
	connectionName = this.amqpClient.defaultKey
	}
	if (!this.amqpClient.clients.has(connectionName)) {
	throw new Error(`client ${connectionName} does not exist`)
	}

This deviates from what NestJS does on modules like @nestjs/mongoose or @nestjs/typeorm where multiple connections are handled by different instances of the module. This is how @nestjs/mongoose handles multiple connections:

@Module({
  imports: [
    MongooseModule.forRoot('mongodb://localhost/test', {
      connectionName: 'cats',
    }),
    MongooseModule.forRoot('mongodb://localhost/users', {
      connectionName: 'users',
    }),
  ],
})
export class AppModule {}

And when wanting to use a resource for a module, an Injector is provided to inject the resource for a particular connection:

export class CatsService {
  constructor(@InjectConnection('cats') private connection: Connection) {}
}

This behavior also deviates from the current implementation where no injection happens, and instead, a shared "AMQPService" is provided to get access to channels. Not doing dependency injection right has implications for testing and goes against core design principles for NestJS.

(Breaking) changes made to fix this behavior

(not a comprehensive list)

• AMQPModule.forRoot now accepts two parameters. The first is for connection details (hostname, port, etc.), and the second is for connection options (exchanges, asserting queues, serviceName, etc.)

forRoot(connection: string | Options.Connect, options: AMQPModuleOptions)

• Created two different NestJS providers on the AMQPCoreModule. One for an AMQP Connection and one for an AMQP Channel.
• New channel and connection token getters for handling multiple connections.
• Exported injectors so a connection/channel can be injected to any class.
  • Removed AMQPService in favor of injectors.

export class JobsService {
  constructor(
    @InjectAMQPChannel('connectionName!')
    private amqpChannel: Channel,
  ) {}

• Moved AMQP initializers (queue assertions, consumer handlers, etc.) from the AMQPModule to the AMQPModuleExplorer.

TO-DOs

• Remove // TODO: from the code (there are still some left)
• Fix E2E test application
• Update README.md with updated examples and explanations.
• forRootAsync support. Closes Need Async initalizing Modules with forRootAsync #14

Closes #3.

[EnriqCG]

Closed in favor of #24.