Handle RabbitMQ disconnects

[xarg]

⚠️ Not ready to merge, please read below

Relates to #100

Features:

• Made exchange durable - the change is explained here: Channel not open after reconnect to RabbitMQ celery/kombu#763
• Always retry sending/consuming after connection errors.

Unresolved issues:

• Since in production environment the exchange and the queues are already declared as durable/non-durable - how can we redeclare them as durable? Is there a way to migrate them? If I just change the durability i get this error: PreconditionFailed: Exchange.declare: (406) PRECONDITION_FAILED - inequivalent arg 'durable' for exchange
• How do I test this?

[miguelgrinberg]

The issue you referenced contains the following statement:

So if you have a non-durable Exchange with some durable Queues attached to it then after restart it's just hangs there zombie like, not able to accept any new consumers

Have you considered making the queues non-durable instead? Doesn't that also solve the issue, without creating durable resources that will then have to be cleaned up by hand if you are just running a quick test?

[xarg]

I just tried making queues non-durable and it worked as expected.

[miguelgrinberg]

@xarg Awesome. Thank you so much!

[xarg]

Thanks for being responsive. I would like add some tests for this as well. I'm not familiar with Travis that much, but does it offer a RMQ server or something?

[miguelgrinberg]

The tests that I currently have on this repository are all unit tests, they do not have access to any real services, they mock the actual services to test that the code does the right thing. Travis does not provide anything to my knowledge, it would be a somewhat large effort to set up a system to run integration tests, at this point, and will likely incur in hosting costs for me, so I keep things limited to unit tests. If you would like to investigate mocking RabbitMQ to test this code, I would gladly accept that.

[xarg]

Got it. Do you think this one is included in the free plan? https://docs.travis-ci.com/user/database-setup/#RabbitMQ

If it's free, would you be open to integrations tests or still want to keep it simple with unittest mocking?

[miguelgrinberg]

Sure. I think there is quite a bit of work to set them up, but it would be good to have them, not only for RabbitMQ but for testing the package in general. Sounds like travis could provide enough infrastructure to get this done. You can create a new PR in which you edit the .travis.yml file to request those extra services, I think that's all you need to get the travis infrastructure in place.

[xarg]

Alright, I'm gonna do it.

[stuartspotlight]

Is this related to my issue with publisher disconnects? celery/kombu#857