How to Update Dependencies on OpenShift

If you are already running some cool application on OpenShift it could be the case that you have to update some of the packages installed as dependencies. Here is an example for an application using the python-2.6 cartridge.

Pull latest upstream packages

The most simple method is to update everything to the latest upstream versions.

1. Backup! Backup! Backup!

   rhc-snapshot -a mycoolapp
   mv mycoolapp.tar.gz mycoolapp-backup-before-update.tar.gz
   

2. If you haven't specified any particular version in setup.py it will look like this:

   ...
   install_requires=[
                   'difio-openshift-python',
                   'MySQL-python',
                   'Markdown',
                  ],
   ...
   

3. To update simply push to OpenShift instructing it to rebuild your virtualenv:

   cd mycoolapp/
   touch .openshift/markers/force_clean_build
   git add .openshift/markers/force_clean_build
   git commit -m "update to latest upstream"
   git push
   

Voila! The environment hosting your application is rebuilt from scratch.

Keeping some packages unchanged

Suppose that before the update you have Markdown-2.0.1 and you want to keep it! This is easily solved by adding versioned dependency to setup.py

-       'Markdown',
+       'Markdown==2.0.1',

If you do that OpenShift will install the same Markdown version when rebuilding your application. Everything else will use the latest available versions.

Note: after the update it's recommended that you remove the .openshift/markers/force_clean_build file. This will speed up the push/build process and will not surprise you with unwanted changes.

Update only selected packages

Unless your application is really simple or you have tested the updates, I suspect that you want to update only selected packages. This can be done without rebuilding the whole virtualenv. Use versioned dependencies in setup.py :

-       'Markdown==2.0.1',
-       'django-countries',
+       'Markdown>=2.1',
+       'django-countries>=1.1.2',

No need for force_clean_build this time. Just

    git commit && git push

At the time of writing my application was using Markdown-2.0.1 and django-countries-1.0.5. Then it updated to Markdown-2.1.1 and django-countires-1.1.2 which also happened to be the latest versions.

Note: this will not work without force_clean_build

-       'django-countries==1.0.5',
+       'django-countries',

Warning

OpenShift uses a local mirror of Python Package Index. It seems to be updated every 24 hours or so. Have this in mind if you want to update to a package that was just released. It will not work! See How to Deploy Python Hotfix on OpenShift if you wish to work around this limitation.