Wait for drain when publish/sendToQueue returns false

[mattiekat]

I am trying to read through the code and I know for a fact I have not seen any waits for the drain event form channel, however, I am not sure if they are needed.

According to the amqplib docs, when publish or sendToQueue returns false, you should wait for the drain event before re-trying. It looks like the code currently just returns false and leaves it to the user to retry; but that requires accessing channelWrapper._channel.on('drain', cb) to do so.

You can find the docs on this at the bottom of this section.

[SimoneDagna]

The same goes for return event.
Accordingly with: https://www.rabbitmq.com/publishers.html

When a published message cannot be routed to any queue, and the publisher set the mandatory message property to true, the message will be returned to it. The publisher must have a returned message handler set up in order to handle the return (e.g. by logging an error or retrying with a different exchange)

channelWrapper.on('return', cb) doesn't work.

Directly attaching event listener using ConfirmChannel inside setup callback seems to work but feels wrong.

[navedmirCM]

Any update on channel drain event? I can see the drain event being fired but no messages are getting dropped. Not sure, whether it is handled in this library. I can't find the code where drain is handled

[richardklafter]

Reading the code if you always await chances are you will never hit the drain issue because this library significantly throttles how quickly you can publish messages. If you just publish 100K+ messages without await you will have a bad day.

//This will work fine because the internal setImmediate call will throttle your publishes to 1 per event loop cycle.
for (let index = 0; index < 500000; index++) {
  await channel.publish(exchange, topic, Buffer.from("yourmessage"+index)
}
//This will bust hard!
for (let index = 0; index < 5000000; index++) {
  channel..publish(exchange, topic, Buffer.from("yourmessage"+index)
}

I might open a PR to fix or I might just purge this library from our code base largely dependent on if its maintainer responds.

[jwalton]

I am more than happy to accept a PR.

[jwalton]

🎉 This issue has been resolved in version 3.2.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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