High cpu when using Gunicorn with multiprocess

I run flask app on Gunicorn 20.0.4 and Kubernetes. My python is v3.7.5. I have a problem with increasing CPU over a time.

After investigating stack traces using py-spy I noticed that the issue is caused by prometheus metrics lib.
It doesn't clean up metric files from old workers. Therefore over a time merge process take more and more CPU.

After deleting following files the CPU usages dropped significantly:

ll -lh
total 7.0M
drwxr-xr-x 2 root root 4.0K Jul 24 06:13 ./
drwxrwxrwt 1 root root 4.0K Jul 19 14:14 ../
-rw-r--r-- 1 root root 1.0M Jul 24 08:14 counter_106.db
-rw-r--r-- 1 root root 1.0M Jul 23 18:41 counter_112.db
-rw-r--r-- 1 root root 1.0M Jul 24 04:07 counter_118.db
-rw-r--r-- 1 root root 1.0M Jul 24 04:54 counter_136.db
-rw-r--r-- 1 root root 1.0M Jul 24 08:40 counter_142.db
-rw-r--r-- 1 root root 1.0M Jul 20 16:44 counter_16.db
-rw-r--r-- 1 root root 1.0M Jul 20 11:24 counter_17.db
-rw-r--r-- 1 root root 1.0M Jul 21 01:40 counter_18.db
-rw-r--r-- 1 root root 1.0M Jul 21 20:14 counter_40.db
-rw-r--r-- 1 root root 1.0M Jul 21 17:17 counter_52.db
-rw-r--r-- 1 root root 1.0M Jul 21 21:29 counter_58.db
-rw-r--r-- 1 root root 1.0M Jul 23 07:19 counter_70.db
-rw-r--r-- 1 root root 1.0M Jul 22 19:49 counter_82.db
-rw-r--r-- 1 root root 1.0M Jul 22 18:59 counter_88.db
-rw-r--r-- 1 root root 1.0M Jul 24 08:43 histogram_106.db
-rw-r--r-- 1 root root 1.0M Jul 24 04:15 histogram_112.db
-rw-r--r-- 1 root root 1.0M Jul 24 05:02 histogram_118.db
-rw-r--r-- 1 root root 1.0M Jul 24 08:43 histogram_136.db
-rw-r--r-- 1 root root 1.0M Jul 24 08:43 histogram_142.db
-rw-r--r-- 1 root root 1.0M Jul 20 16:46 histogram_16.db
-rw-r--r-- 1 root root 1.0M Jul 20 11:45 histogram_17.db
-rw-r--r-- 1 root root 1.0M Jul 21 01:51 histogram_18.db
-rw-r--r-- 1 root root 1.0M Jul 21 22:41 histogram_40.db
-rw-r--r-- 1 root root 1.0M Jul 21 17:45 histogram_52.db
-rw-r--r-- 1 root root 1.0M Jul 22 01:44 histogram_58.db
-rw-r--r-- 1 root root 1.0M Jul 23 07:37 histogram_70.db
-rw-r--r-- 1 root root 1.0M Jul 23 01:01 histogram_82.db
-rw-r--r-- 1 root root 1.0M Jul 22 23:40 histogram_88.db

The issue is related to https://github.com/prometheus/client_python/issues/275

Can we avoid that somehow without periodically restating the k8s pod? Maybe multiprocess should use PID + UUID generated on worker rather than just PID for file names? So master could remove/merge files from dead workes?

Commencez par reproduire la configuration multiprocessus de Gunicorn décrite dans l’issue et examinez comment le processus de merge gère les fichiers counter_.db et histogram_.db listés provenant d’anciens workers. L’issue renvoie à client_python#275 pour le contexte associé. Le travail est considéré comme terminé lorsqu’il empêche les fichiers obsolètes des workers de provoquer une augmentation de l’utilisation du CPU sans nécessiter de redémarrages périodiques des pods Kubernetes.