Emit signal.worker_init in prefork pool child process

[milos-u]

Checklist

• I have checked the issues list
  for similar or identical enhancement to an existing feature.
• I have checked the pull requests list
  for existing proposed enhancements.
• I have checked the commit log
  to find out if the if the same enhancement was already implemented in the
  master branch.
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  (If there are none, check this box anyway).

Related Issues and Possible Duplicates

Related Issues

• None

Possible Duplicates

• None

Brief Summary

From my manual observation, child process from the prefork pool does not emit signal.worker_init under Windows when starting.

With this patch:

--- a/celery/concurrency/prefork.py
+++ b/celery/concurrency/prefork.py
@@ -78,6 +78,7 @@ def process_initializer(app, hostname):
                                       app=app)
     from celery.worker import state as worker_state
     worker_state.reset_state()
+    signals.worker_init.send(sender=None)
     signals.worker_process_init.send(sender=None)

first the Django worker_fixup is installed (in worker_init signal callback) and then Django fixup on_worker_process_init is called (in worker_process_init signal callback).

Without this patch, Django is not initialized inside the child process (django.setup() is not called).

Design

Architectural Considerations

None

Proposed Behavior

Proposed UI/UX

Diagrams

N/A

Alternatives

None

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[auvipy]

can you come with proposed patch with an integration & unit test?

[milos-u]

I can try, right now a lot of work elsewhere, will take a look at it.