Properly closing a connection in Node.JS

[Andras Barthazi]

Hi,

I'm wondering how can I properly close a connection with Node.JS and amqplib.

Here's my code: https://gist.github.com/boogie/79dc497f0b9fe80fad0aa0ef3ef52d98

If there are a lot of messages in the queue, and I'm terminating the connection, I can see this error:

 [x] Received '"jjdjdj"'

 [x] Received '"jjdjdj"'

 [x] Received '"jjdjdj"'

 [x] Received '"jjdjdj"'

 [*] Finished

(node:72547) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): IllegalOperationError: Channel closed

(node:72547) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Any ideas what am I doing wrong?

Thanks,

  Andras

[Michael Klishin]

I'm not an expert on promise libraries but the warning seems to say that you did not define

a handler for the error (rejection) path. However,

> IllegalOperationError: Channel closed

suggests that you may be double closing a channel? A channel can be closed by the server in case

of certain errors, they are easy to post in server logs.

To cleanly close a connection you need to close conn, not just the channel. That's not
technically required but will avoid noise in server logs.

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MK

Staff Software Engineer, Pivotal/RabbitMQ

[Andras Barthazi]

Hi Michael,

Thanks for your answer, it helped me figuring out the problem is with acking a message after the channel have been closed.

So if I catch the error with a try catch around ch.ack(msg);, then it's a bit better, but that message should be acked.

This is my latest code: https://gist.github.com/boogie/dbb8ca7e9f3168347d31cb0f082732ef

- introduced a counter variable processing -- if it's zero, then no messages are processed, so it's safe to close the channel

- added cancelling the consumer, it should stop new messages coming

- when no messages are processed anymore (retrying it every 100 ms), then I'm closing the channel and the connection

It seems to be working, but I'm interested in any thoughts about this solution.

Bye,

  Andras

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MK

Staff Software Engineer, Pivotal/RabbitMQ

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