Avoid metrics collection workers unless endpoint

[moolitayer]

Starting with k8s since container_manager_mixin is shared with openshift.
We will then need to do one of:

• copy emses_in_zone to openshift's metrics_collector_worker.rb
  OR
• create a common component for both metrics collectors

supports_metrics? aims to be replaced by a support feature.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1437138#c0

[moolitayer]

cc @durandom @yaacov @cben @simon3z

[yaacov]

LGTM 👍

Note:
The check connection_configurations.hawkular != nil will not work on systems where we have a hawkular with nil hostname, which is the way we check for supports_metrics? now.

[durandom]

• I would not call the arg hawkular, because supports_metrics? just returns a boolean. How about available or supported
• the ()are not needed
• Typo: supporty vs supports

[durandom]

I'm ok with adding the method before adding a feature. @moolitayer just be sure to push adding the feature once you have a full featured and working implementation

[miq-bot]

Checked commit moolitayer@3d26da2 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
2 files checked, 0 offenses detected
Everything looks fine. 🍰

[cben]

Nice.
@yaacov is right. Backward compatibility is hard, depends on when provider was Added (or last Edited):

• ≤capablanca was creating single-endpoint providers. their metrics did work on ≥darga if they had it on master port 5000 (or by changing metrics_port setting). though on capablanca itself I don't see this code (no hawkular_client_mixin.rb, no metrics_port).
  Are you OK with such providers no longer getting metrics (requiring manual Edit to fix)?

• ≥darga always created hawkular endpoints, sometimes with empty hostname.
  I suppose such providers will just continue to try (and fail) getting metrics, we can later do a migration deleting empty-hostname endpoints...

[durandom]

👍

[simon3z]

@moolitayer @cben any label? (bug? enhancement? backport? etc.)

[moolitayer]

@simon3z should reach 5.8.1
@miq-bot add_label enhancement, fine/yes

[simaishi]

@moolitayer @simon3z BZ 1437138 is now for 'master' only. In the BZ, it says it's safe to backport this alone, but not sure what issue this will fix. Should this still be backported?

[moolitayer]

I was just on my way here... Better not to backport

@miq-bot add_label fine/no