Running Locust without the web UI

You can run locust without the web UI - for example if you want to run it in some automated flow, like a CI server - by using the --headless flag together with -u and -r:

$ locust -f locust_files/my_locust_file.py --headless -u 1000 -r 100

-u specifies the number of Users to spawn, and -r specifies the spawn rate (number of users to start per second).

Setting a time limit for the test

If you want to specify the run time for a test, you can do that with --run-time or -t:

$ locust -f --headless -u 1000 -r 100 --run-time 1h30m

Locust will shutdown once the time is up.

Allow tasks to finish their iteration on shutdown

By default, locust will stop your tasks immediately (without even waiting for requests to finish). If you want to allow your tasks to finish their iteration, you can use --stop-timeout <seconds>.

$ locust -f --headless -u 1000 -r 100 --run-time 1h30m --stop-timeout 99

Running Locust distributed without the web UI

If you want to run Locust distributed without the web UI, you should specify the --expect-workers option when starting the master node, to specify the number of worker nodes that are expected to connect. It will then wait until that many worker nodes have connected before starting the test.

Controlling the exit code of the Locust process

When running Locust in a CI environment, you might want to control the exit code of the Locust process. You can do that in your test scripts by setting the process_exit_code of the Environment instance.

Below is an example that’ll set the exit code to non zero if any of the following conditions are met:

• More than 1% of the requests failed

• The average response time is longer than 200 ms

• The 95th percentile for response time is larger than 800 ms

import logging
from locust import events

@events.quitting.add_listener
def _(environment, **kw):
    if environment.stats.total.fail_ratio > 0.01:
        logging.error("Test failed due to failure ratio > 1%")
        environment.process_exit_code = 1
    elif environment.stats.total.avg_response_time > 200:
        logging.error("Test failed due to average response time ratio > 200 ms")
        environment.process_exit_code = 1
    elif environment.stats.total.get_response_time_percentile(0.95) > 800:
        logging.error("Test failed due to 95th percentile response time > 800 ms")
        environment.process_exit_code = 1
    else:
        environment.process_exit_code = 0

(this code could go into the locustfile.py or in any other file that is imported in the locustfile)