Quick startΒΆ

Below is a quick little example of a simple locustfile.py:

from locust import Locust

def login(l):
    l.client.post("/login", {"username":"ellen_key", "password":"education"})

def index(l):

def profile(l):

class WebsiteUser(Locust):
    tasks = {index:2, profile:1}

    def on_start(self):

Here we define a number of locust tasks, which are normal Python callables that take one argument (a Locust class instance). These tasks are gathered under a Locust class in the task attribute.

Another way we could declare a Locust class, that might be more convenient, is to use the @task decorator. The following code is equivalent to the above:

from locust import Locust

class WebsiteUser(Locust):

    def on_start(self):
        """ on_start is called when a Locust start before any task is scheduled """

    def login(self):
        self.client.post("/login", {"username":"ellen_key", "password":"education"})

    def index(self):

    def profile(self):

The Locust class also allows one to specify minimum and maximum wait time - per simulated user - between the execution of tasks (min_wait and max_wait) as well as other user behaviours.

To run Locust with the above locust file, if it was named locustfile.py, we could run (in the same directory as locustfile.py):


or if the locust file is located elsewhere we could run:

locust -f ../locust_files/my_locust_file.py

To run Locust distributed across multiple processes we would start a master process by specifying –master:

locust -f ../locust_files/my_locust_file.py --master

and then we would start an arbitrary number of slave processes:

locust -f ../locust_files/my_locust_file.py --slave

If we want to run locust distributed on multiple machines we would also have to specify the master host when starting the slaves (this is not needed when running locust distributed on a single machine, since the master host defaults to

locust -f ../locust_files/my_locust_file.py --slave --master-host=


To see all available options type

locust –help

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