Stop Redis connection from preventing shutting down the service

[hectorgomezv]

Closes #73

This PR aims to prevent Redis connection retries from stopping service shutdown.

I think the main problem was the service used client.quit() to gracefully disconnect from Redis instance, and this forces the app to wait until the Redis instance acknowledges the connection end. The problem arises when the Redis instances is not reachable for any reason (socket issues, the instance is not running, etc.), there is a similar issue open in the node-redis repository.

So the solution I implemented is to define a timeout which will fire a client.disconnect() if the instance doesn't respond in time. I've set a 2 seconds grace period for the server to respond, but we could change this if you think so, or even we could extract this into a configuration param/env variable.

[coveralls]

Coverage decreased (-0.3%) to 88.728% when pulling 968af6e on 73-shutdown-hook-not-working-while-trying-to-connect-to-redis into 905f6fe on main.

[fmrsabino]

disconnect returns a Promise shouldn't we make forceQuit async? How does that play with the bind() in setTimeout?

[hectorgomezv]

Yes, maybe it's more correct to define it as async and wait for the Promise to be resolved. Solved here. Thanks.

bind() creates a new function but doing a closure over this (i.e. saving the caller context). Otherwise setTimeout callback (forceQuit function) won't have access to the context when fired. This is necessary to still having access to this.client to invoke disconnect.

[fmrsabino]

Do you know about: https://nodejs.org/api/timers.html#timers-promises-api

I did a quick mockup with the following:

import { setTimeout } from 'timers/promises';

...

async onModuleDestroy(): Promise<void> {
  const abortController = new AbortController();
  this.logger.verbose('Closing Redis connection');

  (async () => {
    await setTimeout(this.quitTimeoutInSeconds * 1000, this.forceQuit(), {
      signal: abortController.signal,
    });
  })();

  await this.client.quit();
  abortController.abort();
  this.logger.verbose('Redis connection closed');
}