Django 3.x / uwsgi is leaking connections

[Marcin Nowak]

Project upgraded from 2.x to 3.0.4 is leaking PostgreSQL database connections.
ATOMIC_REQUESTS=False, AUTOCOMMIT=True, CONN_MAX_AGE=0
UWSGi threads are enabled (--enable-threads)
Python 3.8.1 and 3.7.3

After few hours all posgtress connections are used (too many connections error).
pg_stat_activity is reporting idle connections with part of queries visible.

I would try to deliver more details later.

Facts:

• setting up CONN_MAX_AGE > 0 does not help
• CONN_MAX_AGE = 30, starting runserver and making many calls with ab -c 10 -n 100 http://127.0.0.1:8000/ uses all available connections and ends with error 500 (due to no available connections)
• CONN_MAX_AGE = 30, starting runserver --nothreading and making calls with ab -c 100 -n 100 http://127.0.0.1:8000/ works fine

CONN_MAX_AGE=30 + runserver + ab scenario is reproducible on clean install. View must call database.
CONN_MAX_AGE=0 + runserver + ab -> cannot reproduce.