Locust is an easy-to-use, distributed, user load testing tool. It is
intended for load-testing web sites (or other systems) and figuring out
how many concurrent users a system can handle.

The behavior of each locust (or test user if you will) is defined by you
and the swarming process is monitored from a web UI in real-time. This
will help you battle test and identify bottlenecks in your code before
letting real users in.

WWW: https://locust.io/