Nestjs CQRS - CommandHandlerNotFoundException - node.js

Question

I am trying to use events in my nestjs app.
However when I attempt to trigger command, I get CommandHandlerNotFoundException.
I have message-bus.module:
#Module({
imports: [CqrsModule],
providers: [
MessageBusLocalService,
StartWorkflowHandler
],
exports: [MessageBusLocalService]
})
export class MessageBusModule {
}
message-bus-local.service
#Injectable()
export class MessageBusLocalService {
constructor(private readonly commandBus: CommandBus, private eb: EventBus) {
}
startWorkflow(workflowId: string, payload: any) {
return this.commandBus.execute(
new StartWorkflowCommand(workflowId, payload)
);
}
}
and start-workflow.handler
#CommandHandler(StartWorkflowCommand)
export class StartWorkflowHandler implements ICommandHandler<StartWorkflowCommand> {
constructor() {}
async execute(command: StartWorkflowCommand) {
console.log('Workflow started', command.jobId);
return true;
}
}
I am trying to trigger command when app is bootstrapped:
const app = await NestFactory.create(ApplicationModule);
const service = app.get(MessageBusLocalService);
try {
const c = await service.startWorkflow('abcde', {just: "test"});
console.log('And returned', c);
} catch (e) {
console.error(e)
}
and... I get the CommandHandlerNotFoundException there although I believe it is declared... What did I do wrong?
Thanks in advance.

Answer 1

Since you want to use the handler in another module (e.g. appModule ) you need to add the #Injectable() decorator to the StartWorkflowHandler class.
And call app.init() in the main.ts. Before starting the application.

Answer 2

Your MessageBusModule does not re-export handlers, thus they are not "visible" on app.module level (at least this is what I understand on my own)
I got similar scenario like that:
const commands = [NewOrder, ChargeForOrder]
const events = [ChargeOrder, OrderProcessed]
const sagas = [AdjustWalletFunds]
#Module({
imports: [
CqrsModule,
WalletsModule,
TypeOrmModule.forFeature([...]),
],
providers: [...commands, ...events, ...sagas],
exports: [CqrsModule, ...commands, ...events, ...sagas],
})
export class RxModule {}
so, assuming you import your MessageBusModule in the main app.module, try the following:
#Module({
imports: [CqrsModule],
providers: [
MessageBusLocalService,
StartWorkflowHandler
],
exports: [MessageBusLocalService, StartWorkflowHandler]
})
export class MessageBusModule {
}

Answer 3

As it turns out, the method I used in the question does not work.
However it does work as expected if I inject the MessageBusLocalService in controller.
It seems odd to answer my own question but it might help someone eventually.

Answer 4

Ensure you imported have CqrsModule imported. Also import the MessageBusModule into any other module where it is called from.