fix: channel deadlock in regexp consumer

[goncalo-rodrigues]

Motivation

When using a regexp consumer, there's a race condition between producing and consuming new discovered topics. If the discover topic takes too long or the auto discovery period is too short, then multiple ticker.C messages may be processed in a row which will block on the subcsribe/unsubscribe channels as they only have a buffer size of 1. This will block new topics from being discovered forever.

Modifications

Moved the consumers into their own goroutines and use an unbuffered channel. There's multiple ways to go about it but it's good practice to keep consumers and producers separate. Consumers are run until the channels they are consumed from are closed, which happens when the producer (monitor) returns.

Verifying this change

• [ x ] Make sure that the change passes the CI checks.

  • *Added integration tests that fail when the patch is not there. There's 2-3 discover calls and then the monitor blocks indefinitely and the topics are not discovered.

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable
• If a feature is not applicable for documentation, explain why? not a feature
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[RobertIndie]

LGTM. Thanks for your contribution.