Fix metric emitting for triggerer and dag processor

[o-nikolas]

After a recent refactoring (#53722) a call to an initializer for stats is required but was not done for the dag processor or triggerer. I noticed this when going to manually test some of my metrics related changes in breeze.

Tested manually in Breeze with and without these changes and metrics appear with these fixes.

I'm curious to hear from @xBis7 since he was the original author of the above changes.

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[xBis7]

Hi @o-nikolas, thanks for pinging me. The initialize method was the best approach we could come up with, me and @potiuk in order to decouple the code from core.

The result is that every new process has to call Stats.initialize during startup. I was able to identify only 3 places based on the existing tests but I was sure there were more. I see now that it was naive of me to not run further manual tests.

[o-nikolas]

Hi @o-nikolas, thanks for pinging me. The initialize method was the best approach we could come up with, me and @potiuk in order to decouple the code from core.

The result is that every new process has to call Stats.initialize during startup. I was able to identify only 3 places based on the existing tests but I was sure there were more. I see now that it was naive of me to not run further manual tests.

Thanks for the context @xBis7 I figured that was the case. Do you mind giving these changes a review?

[xBis7]

@o-nikolas What are you using for testing? StatsD?

[o-nikolas]

@o-nikolas What are you using for testing? StatsD?

Yup!

breeze start-airflow --backend postgres --integration statsd

[xBis7]

Changes LGTM! I tested it manually and I was able to reproduce the issue and verify that the changes in this patch, fix it. Thanks!