Infer interruption adapter from queue adapter, take 2

[Mangara]

This PR is an attempt to redo #367 in a backwards compatible way. That will allow us to release this as 1.x, and remove the deprecations in 2.0.

Future behaviour

Like that PR, the desired interface going forward is:

• Interruption adapters get registered (automatically for ones that job-iteration knows about, manually for others):

# happens automatically if resque is available
JobIteration::InterruptionAdapters.register(:resque, JobIteration::InterruptionAdapters::ResqueAdapter) 

# the default can be overridden
JobIteration::InterruptionAdapters.register(:sidekiq, MyCustomSidekiqAdapter) 

# custom interruption adapter for queue adapters that job-iteration doesn't know about
JobIteration::InterruptionAdapters.register(:awesome_queue, AwesomeQueueAdapter) 

• At runtime, job-iteration looks up the interruption adapter based on the queue_adapter_name of the job class.

def interruption_adapter
  JobIteration::InterruptionAdapters.lookup(queue_adapter_name)
end

Backwards compatibility

The major differences are that:

• At lookup time, if JobIteration.interruption_adapter is set, we use that instead:

def interruption_adapter
  JobIteration.interruption_adapter || JobIteration::InterruptionAdapters.lookup(queue_adapter_name)
end

• Instead of removing JobIteration.interruption_adapter=, we print a deprecation warning:

> JobIteration.interruption_adapter = Foo.new
DEPRECATION WARNING: Setting JobIteration.interruption_adapter is deprecated. Use JobIteration::InterruptionAdapters.register(:foo, callable) instead to register the callable (a proc, method, or other object responding to #call) as the interruption adapter for queue adapter :foo.

• Instead of raising when we don't find a matching queue adapter (and JobIteration.interruption_adapter is not set), we log a deprecation warning:

DEPRECATION WARNING: No interruption adapter is registered for :fancy_queue; falling back to `NullAdapter`, which never interrupts.
Use `JobIteration::InterruptionAdapters.register(:fancy_queue, <adapter>) to register one.
This will raise starting in version 2.0 of JobIteration!"

[Mangara]

@bdewater Sorry it's taken us so long to get this change out. I hope this gives us a good way to move forward. I can't seem to tag you as reviewer, but I'd welcome your input.

[bdewater]

Left a few small comments but it's looking good! Thanks @Mangara and @sambostock. Also cc'ing @plasticine for the original PR I based my work on.

[sambostock]

Is this considered part of the public API? Seems unlikely someone would be referencing the constant though.

[Mangara]

The only references I can find in GitHub are RBI files: https://github.com/search?q=JobIteration%3A%3AIntegrationLoadError&type=code
I highly doubt anyone was rescuing this.

[sambostock]

Sounds good. Good reminder for us to ensure we're masking things as # @api private though, as we are with the built in adapters constant.

[sambostock]

Having this method as a class method allowed the job class to overwrite it, which feels like it would be useful in tests, if nothing else (since we plan to get rid of the global JobIteration.interruption_adapter).

By moving the logic into the private method marked as @private, we've made it so it can't be controlled without violating the privacy contract.

Is that something we should reconsider?

[Mangara]

Discussed offline, but I feel like for tests we can register a configurable TestAdapter for when the test queue adapter is used. For other cases, I agree there's a missing configuration option, but I'm not convinced the interruption adapter is the right place for that. I like keeping its scope small - to tell us when the job worker is stopping.

[sambostock]

I could have sworn there was a cop that forced trailing spaces and spaces before the \...

Suggested change

	Deprecation.warn("Setting JobIteration.interruption_adapter is deprecated."\
	" Use JobIteration::InterruptionAdapters.register(:foo, callable) instead"\
	" to register the callable (a proc, method, or other object responding to #call)"\
	" as the interruption adapter for queue adapter :foo.")
	Deprecation.warn("Setting JobIteration.interruption_adapter is deprecated. " \
	"Use JobIteration::InterruptionAdapters.register(:foo, callable) instead " \
	"to register the callable (a proc, method, or other object responding to #call) " \
	"as the interruption adapter for queue adapter :foo.")

[Mangara]

There is, LineContinuationLeadingSpace, and it should be enabled.

[Mangara]

Not sure why it wasn't flagging this, but I fixed the spaces.

[sambostock]

Ahh, while we do have it enabled on rubocop-shopify@main, it's still disabled in the latest release (v2.14.0), which is what this repo is using.