objc[54401]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.

[dmd]

Putting this here so anyone else using rq with requests can find it.

On a brand new install of rq, e.g., create a new python3.9 virtualenv and pip install rq:

❯ python
Python 3.9.1 (default, Feb  3 2021, 07:38:02)
[Clang 12.0.0 (clang-1200.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from redis import Redis
>>> from rq import Queue
>>> q = Queue(connection=Redis())
>>> import requests
>>> q.enqueue(requests.get, 'http://example.com')
Job('2aa722f8-c408-4dfa-a74d-fe0b2934fced', enqueued_at=datetime.datetime(2021, 2, 18, 17, 30, 4, 443845))
>>>

Then,

❯ rq worker
12:36:37 Worker rq:worker:9375eef5aeb14c0da30782a71f48ff23: started, version 1.7.0
12:36:37 Subscribing to channel rq:pubsub:9375eef5aeb14c0da30782a71f48ff23
12:36:37 *** Listening on default...
12:36:37 default: requests.api.get('http://3e.org') (d334dc61-7ec3-4287-acd0-deea546be9ba)
objc[54724]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[54724]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
12:36:38 Moving job to FailedJobRegistry (work-horse terminated unexpectedly; waitpid returned 6)

The solution is:

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
rq worker

[manmat]

This helped me solve the same error when using functions_framework to test Google Cloud Functions locally. Many thanks

[amotl]

Dear Daniel,

thanks a stack, this saved my day when I was trying to invoke a worker function using Python's multiprocessing module.

With kind regards,
Andreas.

[supermandavid]

I have been searching every where for this

you are God send.

[asennoussi]

This doesn't seem to work under Monterey anymore.
Any idea how to solve it?

[stevenhaley]

This doesn't seem to work under Monterey anymore. Any idea how to solve it?

@Sshuichi: I'm using Monterey (12.3 21E230) and it still worked for me. 🎉 Unfortunately that probably means you've got a different issue to resolve.

[kernelguardian]

For anyone wondering why this works
Apple changed macOS fork() behaviour since High Sierra. The OBJC_DISABLE_INITIALIZE_FORK_SAFETY=yes variable turns off the immediate crash behaviour that their newer ObjectiveC framework usually enforces now by default. This can affect any language that is doing multithreading / multiprocessing using fork() on macOS >= 10.13, especially when "native extensions" / C code extensions are used.

Reference
StackOverflow Link

[odoublewen]

A relevant blog post that also suggests the same fix:
https://hynek.me/til/rq-macos/

The author includes this warning:

Be aware that this is akin to taking the batteries out of your smoke detector to stop the annoying beeping. fork() should only be used if you immediately exec() afterwards – if at all.

[mambajoe]

thanks for that info, it saved my day... was blocked for that error

[PranjalAgni]

Finally it got solved, that one export line took 1 day for me but now its fine