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Alexis Métaireau
91159ecc80
- More categories are displayed - Change the URL Scheme for categories - Add a view for weeknotes, readings and code.
57 lines
2 KiB
Markdown
57 lines
2 KiB
Markdown
---
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tags: django, pytest
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---
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# Profiling and speeding up Django and Pytest
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[Éloi](https://yaal.coop/) made [a pull request on
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IHateMoney](https://github.com/spiral-project/ihatemoney/issues/1214) to
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speedup the tests, with some great tooling for pytest that I wasn't aware of:
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- [pytest-xdist](https://pypi.org/project/pytest-xdist/) allows to run tests in
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parallel, using `-n auto`
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- [pytest-profiling](https://pypi.org/project/pytest-profiling/) makes it easy
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to get the call stack and time the function calls that take most of the time.
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- You can them analyse the `.prof` files with
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[Snakeviz](https://pypi.org/project/snakeviz/)
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So, I spent some time using these on the tests for [La
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Chariotte](https://chariotte.fr), because they were slow.
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I found two things :
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- Login calls are costly in the test, and it's possible to speed things up ;
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- On my machine, calls to resolve my hostname were slow, using 5s during the
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tests for a lookup that wasn't even useful.
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## Changing the hashing algorithm to speedup tests
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By default, Django uses a slow (but secure !) hashing mechanism for checking
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the user credentials. In the tests, we don't need this security, but we need
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the speed.
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Changing them to use MD5 turns out to be a way to greatly speed them up! Here
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is how to do it with a pytest fixture :
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```python
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@pytest.fixture(autouse=True)
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def password_hasher_setup(settings):
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# Use a weaker password hasher during tests, for speed
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settings.PASSWORD_HASHERS = [
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"django.contrib.auth.hashers.MD5PasswordHasher",
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]
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```
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## Speeding DNS lookups
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I'm currently using a MacOSX machine, and for for whatever reason, the local
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lookup was not configured properly on my machine. I don't think I did anything
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specific to get this wrong, so it might be your case too. Calls to resolve the
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local domain were tooking 5s.
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If the answer to `scutil --get LocalHostName`, `hostname` and `scutil --get
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HostName` differ, then you might be in this case. Here is the fix :
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```bash
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sudo scutil --set HostName <YourHostName>
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```
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