[Typescript] chore: list producer "on" event methods by event name

[hilleer]

What

Accordingly to the producer standard API documentation there are event listener methods available on the Producer instance but those are not currently listed in the typings, making it difficult to find programmatically as well as showing typescript type errors: Property 'on' does not exist on type 'Producer'.ts(2339):

From the docs:

This pull-request adds type definitions for the on event emitter for the event names ready and event.error described in the documentation. There might be more events available?

Checklist

• Contains customer facing changes? Including API/behavior changes
• Did you add sufficient unit test and/or integration test coverage for this PR?
  • If not, please explain why it is not required

Test & Review

Open questions / Follow-ups

• Are there any more event names to be listed?

[milindl]

Hey @hilleer , the 'on' methods aren't supported on the promisified producer (which is typed in kafkajs.d.ts). The documentation you've attached is from the "Callback-Based API" section, which is typed in rdkafka.d.ts, where there are typings for the events and Producer indirectly extends EventEmitter.

[hilleer]

Hey @hilleer , the 'on' methods aren't supported on the promisified producer (which is typed in kafkajs.d.ts). The documentation you've attached is from the "Callback-Based API" section, which is typed in rdkafka.d.ts, where there are typings for the events and Producer indirectly extends EventEmitter.

So we are considering the promisified API to work fully in sequential order and have no need for event listeners here?

[milindl]

Right, we're attempting to do that. For instance, if you await producer.connect(), it's actually internally using the same 'ready' event, so the waiting ends only when the producer is ready. Similarly, awaited methods throw/reject if there's an error.

There are some exceptions at the moment, for instance, for the consumer rebalances, you need to use a rebalance callback within the config. But, for the most part, you should be able to use the API in sequential order.