How to pin all of your Aldryn Django project’s Python dependencies¶
Pinning dependencies is good practice¶
If a dependency is unpinned (that is, a particular version is not specified in the project’s requirements) pip will install the latest version it finds, even if a different version was previously installed. This can cause your your project to fail with an deployment error or worse, a runtime error, the next time it is built - even if you didn’t change anything in it yourself.
We strongly recommend that when you add a dependency to a project via its
requirements.in that you pin it to a
particular version, by specifying its version number.
For example, if you use
rsa and know that version
1.3.4 works, specify it:
That way if a newer, incompatible version of the package is released, your project will still install the correct version the next time you build or redeploy it.
What about dependencies of dependencies?¶
However, dependencies can in turn themselves have dependencies. Even if you pin your requirements, their dependencies may be unpinned.
For example, your project may specify
some-package==1.2.3, but if
rsa in its
requirements, then the next time the project is built, it will attempt to do so using the latest version of
which might not be compatible.
The solution is to pin all the dependencies in your project.
First, you need to have a working local set-up.
Now you can run:
docker-compose run --rm web pip-reqs compile
You won’t see any output, but you will now find a
requirements.txt file in the project,
containing a list of all the packages in the environment, along with their versions.
When your project is built using the new
requirements.txt instead of
you’ll have a guarantee that no unexpected changes will be permitted to find their way in to the
In order to have your project built using
requirements.txt instead of
need to remove the
pip-reqs compile instruction from your project’s
You can do this in two different ways:
- Locally: edit the
Dockerfileto remove the
- Let the Control Panel do it: push your
requirements.txtfile to the project’s repository. At the next deployment, the Control Panel will recognise the file and amend the
If you later remove the
requirements.txt file, the Control Panel will recognise this and will
pip-reqs compile instruction to the
Dockerfile when the project is next
deployed. Alternatively you can restore it locally yourself.
If the relevant sections in the
Dockerfile are surrounded by the Divio-specific comment tags:
# <PYTHON> ... # </PYTHON>
remove these tags - otherwise the Control Panel will simply overwrite your changes.
See the Dockerfile reference for more information about how
the Control Panel populates the
Re-compile when required¶
Any time a change is made to
requirements.in, or to any addons in the project, you will need to
requirements.txt. If the change is made to an addon via the Divio Control Panel, you
will need to:
- pull the latest changes to your local repository
docker-compose run --rm web pip-reqs compileto compile the pinned requirements
- rebuild it locally to check that it works as expected
- push the updated
requirements.txtback to the cloud.