Gunicorn worker terminated with signal 9

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I am running a Flask application and hosting it on Kubernetes from a Docker container. Gunicorn is managing workers that reply to API requests.

The following warning message is a regular occurrence, and it seems like requests are being canceled for some reason. On Kubernetes, the pod is showing no odd behavior or restarts and stays within 80% of its memory and CPU limits.

[2021-03-31 16:30:31 +0200] [1] [WARNING] Worker with pid 26 was terminated due to signal 9

How can we find out why these workers are killed?

I encountered the same warning message.

[WARNING] Worker with pid 71 was terminated due to signal 9

I came across this faq, which says that “A common cause of SIGKILL is when OOM killer terminates a process due to low memory condition.”

I used dmesg realized that indeed it was killed because it was running out of memory.

Out of memory: Killed process 776660 (gunicorn)

In our case application was taking around 5-7 minutes to load ML models and dictionaries into memory. So adding timeout period of 600 seconds solved the problem for us.

gunicorn main:app --workers 1 --worker-class uvicorn.workers.UvicornWorker --bind --timeout 600

In my case the problem was in long application startup caused by ml model warm-up (over 3s)

I encountered the same warning message when I limit the docker’s memory, use like -m 3000m.

see docker-memory


gunicorn-Why are Workers Silently Killed?

The simple way to avoid this is set a high memory for docker or not set.

I was using AWS Beanstalk to deploy my flask application and I had a similar error.

  • In the log I saw:
  • web: MemoryError
  • [WARNING] Worker with pid XXXXX was terminated due to signal 9

I was using the t2.micro instance and when I changed it to t2.medium my app worked fine. In addition to this I changed to the timeout in my nginx config file.

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