ClassificationModel: predict() hangs forever in uwsgi worker

Describe the bug

When model.predict is invoked in a uwsgi worker, it never resolves (hangs on the line outputs = model(**inputs) )

To Reproduce Steps to reproduce the behavior:

• Train a roberta-base model with simpletransformers 0.48.9
• Run a uwsgi + flask server that loads the model with {"use_multiprocessing": False} before spawning workers, and then runs model.predict() when it receives a request (I used the docker image tiangolo/uwsgi-nginx-flask as a base, and install transformers, pytorch and simpletransformers)
• Emit a request, it hangs on the line outputs = model(**inputs)
• However, if model.predict() is called on the same server before the uwsgi workers are spawn (when the server loads, as opposed to when responding to a request), it returns normally with the expected result.
• Another way for predict() to return normally is to load the model inside each worker, meaning the first request handled by each worker is delayed by the loading of the model.

Desktop (please complete the following information):

• Docker image with Debian Buster + python 3.8 + flask + nginx + uwsgi
• transformers version 3.3.1
• simpletransformers version 0.48.9
• torch version 1.6.0
• uwsgi: tested with versions 2.0.17, 2.0.18, 2.0.19, 2.0.19.1

[sukrubezen]

I had the same problem and now I solved it.

My args dict is like below.

args={"use_multiprocessing": False, "use_multiprocessing_for_evaluation": False, "process_count": 1}

[ThilinaRajapakse]

Setting use_multiprocessing=False should fix it.