Tracking Gunicorn's busy worker count

I was investigating performance issues of a Django application running with Gunicorn behind a Nginx server. First, I added more timing information to Nginx access.log: log_format timing '$remote_addr - $remote_user [$time_local] ' '"$request" $status $body_bytes_sent ' '"$http_referer" "$http_user_agent" rt="$request_time" uct="$upstream_connect_time" uht="$upstream_header_time"…