mirror of https://github.com/locustio/locust.git
117 lines
4.2 KiB
ReStructuredText
117 lines
4.2 KiB
ReStructuredText
.. _running-in-debugger:
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===========================
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Running tests in a debugger
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===========================
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Running Locust in a debugger is extremely useful when developing your tests. Among other things, you can examine a particular response or check some User instance variable.
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But debuggers sometimes have issues with complex gevent-applications like Locust, and there is a lot going on in the framework itself that you probably aren't interested in. To simplify this, Locust provides a method called :py:func:`run_single_user <locust.debug.run_single_user>`:
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.. literalinclude:: ../examples/debugging.py
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:language: python
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It implicitly registers an event handler for the :ref:`request <extending_locust>` event to print some stats about every request made:
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.. code-block:: console
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type name resp_ms exception
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GET /hello 38 ConnectionRefusedError(61, 'Connection refused')
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GET /hello 4 ConnectionRefusedError(61, 'Connection refused')
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You can configure exactly what is printed by specifying parameters to :py:func:`run_single_user <locust.debug.run_single_user>`.
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Make sure you have enabled gevent in your debugger settings.
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Debugging Locust is quite easy with Vscode:
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- Place breakpoints
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- Select a python file or a scenario (ex: ```examples/basic.py``)
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- Check that the desired virtualenv is correctly detected (bottom right)
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- Open the action *Debug using launch.json*. You will have the choice between debugging the python file, the scenario with WebUI or in headless mode
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- It could be rerun with the F5 shortkey
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VS Code's ``launch.json`` looks like this:
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.. literalinclude:: ../.vscode/launch.json
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:language: json
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If you want to the whole Locust runtime (with ramp up, command line parsing etc), you can do that too:
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.. literalinclude:: ../.vscode/launch_locust.json
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:language: json
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There is a similar setting in `PyCharm <https://www.jetbrains.com/help/pycharm/debugger-python.html>`_.
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.. note::
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| VS Code/pydev may give you warnings about:
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| ``sys.settrace() should not be used when the debugger is being used``
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| It can safely be ignored (and if you know how to get rid of it, please let us know)
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You can execute run_single_user multiple times, as shown in `debugging_advanced.py <https://github.com/locustio/locust/tree/master/examples/debugging_advanced.py>`_.
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Print HTTP communication
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========================
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Sometimes it can be hard to understand why an HTTP request fails in Locust when it works from a regular browser/other application. Here's how to examine the communication in detail:
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For ``HttpUser`` (`python-requests <https://requests.readthedocs.io/>`_):
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.. code-block:: python
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# put this at the top of your locustfile (or just before the request you want to trace)
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import logging
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from http.client import HTTPConnection
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HTTPConnection.debuglevel = 1
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logging.basicConfig()
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logging.getLogger().setLevel(logging.DEBUG)
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requests_log = logging.getLogger("requests.packages.urllib3")
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requests_log.setLevel(logging.DEBUG)
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requests_log.propagate = True
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For ``FastHttpUser`` (`geventhttpclient <https://github.com/gwik/geventhttpclient/>`_):
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.. code-block:: python
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import sys
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...
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class MyUser(FastHttpUser):
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@task
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def t(self):
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self.client.get("http://example.com/", debug_stream=sys.stderr)
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Example output (for FastHttpUser):
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.. code-block:: console
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REQUEST: http://example.com/
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GET / HTTP/1.1
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user-agent: python/gevent-http-client-1.5.3
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accept-encoding: gzip, deflate, br, zstd
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host: example.com
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RESPONSE: HTTP/1.1 200
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Content-Encoding: gzip
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Accept-Ranges: bytes
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Age: 460461
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Cache-Control: max-age=604800
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Content-Type: text/html; charset=UTF-8
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Date: Fri, 12 Aug 2022 09:20:07 GMT
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Etag: "3147526947+ident"
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Expires: Fri, 19 Aug 2022 09:20:07 GMT
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Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
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Server: ECS (nyb/1D20)
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Vary: Accept-Encoding
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X-Cache: HIT
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Content-Length: 648
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<!doctype html>
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<html>
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<head>
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...
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These approaches can of course be used when doing a full load test, but you might get a lot of output :) |