Locust: Question: debugging in pycharm (or other arbitrary IDE)

[paul-nelson-baker]

Hello, so quick question. I have locust installed in a venv on python 3 (locustio==0.8a2). I've been building and testing a locust python script, but I'm trying to traverse some complicated json responses. In order to run a locust script, you have to run locust loadtest-file.py

Is it possible to attach a debugger while running a locust script?

[cgoldberg]

not really an answer, but a few comments:

Is it possible to attach a debugger while running a locust script?
I've been building and testing a locust python script, but

a locustfile is a normal python file, so you can debug it directly without the rest of the framework. It's easier to debug a single Locust than a swarm.

I'm trying to traverse some complicated json responses.

add code so your Locust class gets created when locustfile is run as a script (not imported) ... you can usually do most script development against a single instance of a Locust.

[MattF-NSIDC]

Took me a minute to get there (specifically to realize I had to call .run()) so I figured I'd share:

I create a subclass of HttpLocust called WebsiteUser. To execute a single instance from the CLI, I added:

if __name__ == '__main__':
    x = WebsiteUser()
    x.run()

Then run python locustfily.py. If I have a pdb breakpoint in one of my tasks, this triggers the breakpoint. Full example locustfile.py:

from locust import HttpLocust, TaskSet, task

class UserBehavior(TaskSet):
    @task
    def index(self):
        import pdb; pdb.set_trace()
        self.client.get("/")

class WebsiteUser(HttpLocust):
    task_set = UserBehavior 
    host = 'http://google.com'
    min_wait = 1000
    max_wait = 2000

if __name__ == '__main__':
    WebsiteUser().run()

[GabLeRoux]

Here I managed to get Intellij Idea (Similar to PyCharm) to break while locust is running.

I used python remote debug run configuration, followed instructions. In my case, I just used a virtualenv and installed locustio and pydevd directly. 🎉

It should break automatically right under the following line (I think break point is optional):

pydevd.settrace('localhost', port=12345, stdoutToServer=True, stderrToServer=True)

👍

[nelsonjchen]

1. Turn on the gevent compatible option in the debugger
2. Run the locust executable as the script, (which locust)

This seems to work for me. Also, note that the remote debug suggestion above requires a paid version of PyCharm or its cousin of a plugin in IntelliJ. I think the steps I have above will work for PyCharm CE as well.

[ad34]

is there a similar tip for visual studio code ?

[dalegaspi]

just to add to what @nelsonjchen has stated, for IntelliJ set the "Script path" to what which locust returns from the command line then set the "Parameters" to -f script_you_want_to_debug.py --host http://whatever. you should be able hit breakpoints where you placed them in script_you_want_to_debug.py

[r3dlin3]

@ad34

is there a similar tip for visual studio code ?

This is what I put in my .vscode\launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Locust",
            "type": "python",
            "request": "launch",
            "module": "locust",
            "args": [
                "-f",
                "${file}",
            ],
            "gevent": true,
            "console": "integratedTerminal"
        }
    ]
}

You can parameters to the args array, if you want an headless experience, set user and hatche rate, the host, etc.

[ffedoroff]

Debug doesn't work in locust >= 1.2.3
To enable debug add env variable:
GEVENT_SUPPORT=True

[ffedoroff]

In locust-plugins you can find debug example:
https://github.com/SvenskaSpel/locust-plugins/blob/master/examples/debug_ex_advanced.py

[GugliEyes]

I use Eclipse with Pydev. In Preferences->PyDev->Debug the 2nd to last option is "Gevent compatible debugging?".

Gevent has to do with the lightweight threading used by Locust ( greenlets ) and I am too ignorant to know much more than that. Once I clicked that, I was able to stop at a breakpoint in my code.

Thanks to all who provided the information and the person who wrote the Single User locust-plugin.