The format of gunicorn's access log can be set in the configuration file. The configuration key is access_log_format.
The default configuration is:
access_log_format = '%(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s"'
We can add %(L)s header to the end. It means request time in decimal seconds.
access_log_format = '%(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s" %(L)s'
If you don't want to use a configuration file, you can add an argument access-logformat to the command line.
Here's an example:
gunicorn app:app --access-logfile /path/to/log --access-logformat '%(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s" %(L)s'
127.0.0.1 - - [16/Jun/2022:18:50:35 +0800] "GET / HTTP/1.1" 200 5 "-" "PostmanRuntime/7.29.0" 3.004339
At the end of the log line, 3.004339 is the request time. It's about 3 seconds.