docs/use-as-lib.rst
.. _use-as-lib:
It is possible to start a load test from your own Python code, instead of running Locust using the locust command.
Start by creating an :py:class:Environment <locust.env.Environment> instance:
.. code-block:: python
from locust.env import Environment
env = Environment(user_classes=[MyTestUser])
The :py:class:Environment <locust.env.Environment> instance's
:py:meth:create_local_runner <locust.env.Environment.create_local_runner>,
:py:meth:create_master_runner <locust.env.Environment.create_master_runner> can then be used to start a
:py:class:Runner <locust.runners.Runner> instance, which can be used to start a load test:
.. code-block:: python
env.create_local_runner()
env.runner.start(5000, spawn_rate=20)
env.runner.greenlet.join()
It is also possible to bypass the dispatch and distribution logic, and manually control the spawned users:
.. code-block:: python
new_users = env.runner.spawn_users({MyUserClass.__name__: 2})
new_users[1].my_custom_token = "custom-token-2"
new_users[0].my_custom_token = "custom-token-1"
The above example only works on standalone/local runner mode and is an experimental feature. A more common/better approach would be to use init or test_start :ref:events to get/create a list of tokens and use :ref:on-start-on-stop to read from that list and set them on your individual User instances.
.. note::
While it is possible to create locust workers this way (using :py:meth:`create_worker_runner <locust.env.Environment.create_worker_runner>`), that almost never makes sense. Every worker needs to be in a separate Python process and interacting directly with the worker runner might break things. Just launch workers using the regular ``locust --worker ...`` command.
We could also use the :py:class:Environment <locust.env.Environment> instance's
:py:meth:create_web_ui <locust.env.Environment.create_web_ui> method to start a Web UI that can be used
to view the stats, and to control the runner (e.g. start and stop load tests):
.. code-block:: python
env.create_local_runner()
env.create_web_ui()
env.web_ui.greenlet.join()
Some packages such as boto3 may have incompatibility when using Locust as a library, where monkey patching is already applied. In this case monkey patching may be disabled by setting LOCUST_SKIP_MONKEY_PATCH=1 as env variable.
.. literalinclude:: ../examples/use_as_lib.py :language: python