Locust errors

Introduction

In this article you will learn about popular Locust problems and their solutions

It is assumed that you work in Ubuntu Linux

I have aliases python - python3 and pip - pip3 set up, so I do not write the trailing 3. The article about it is called «Bash Python alias»

System open file limit '1024' is below minimum setting

You run the command

locust

And get the following warning

[2020-10-27 10:36:12,176] andrei-ubuntu/WARNING/locust.main: System open file limit '1024' is below minimum setting '10000'. It's not high enough for load testing, and the OS didn't allow locust to increase it by itself. See https://github.com/locustio/locust/wiki/Installation#increasing-maximum-number-of-open-files-limit for more info.

The minimum number of simultaneously open files must be 10 000 or more. Otherwise locust cannot work properly

To check the limit for your Linux use the command

cat /proc/sys/fs/file-max

9223372036854775807

9223372036854775807 is my absolute ceiling. But we care about limits for third-party programs

Study the limits with ulimit: -Hn for the hard limit and -Sn for the soft one setrlimit

ulimit -Sn

1024

1024 is exactly the value locust complained about

Raise the limit

ulimit -Sn 10001

ulimit -Sn

10001

locust

locust: error: unrecognized arguments: --no-web

You try to run the test without a UI and execute the command

locust -f locustfile.py --host=https://my-site.com --no-web -u 100 -r 10

And get the following warning

locust: error: unrecognized arguments: --no-web

Replace --no-web with --headless because that is what the Locust developers decided

NameError: name 'between' is not defined

You try to set wait_time

NameError: name 'between' is not defined

Most likely you simply forgot to plug in between

Add

from locust import between

libuv only supports millisecond timer resolution

You try to run the test with between and get

c:\users\andrei\pycharmprojects\locust_demo\lib\site-packages\gevent\hub.py:158: UserWarning: libuv only supports millisecond timer resolution; all times less will be set to 1 ms with loop.timer(seconds, ref=ref) as t:

Most likely you set the minimum value to 0, e.g. wait_time = between(0, 0.4)

Set a non-zero value, e.g. 0.01