How To Contribute a driver to Cinder
Deadline for Kilo
For clarification, a patch is considered a new driver when it's introducing a new protocol into the driver. For example, if your driver supports ISCSI, but your patch proposes support for FibreChannel, that's a new driver patch. Another example, if your driver has some proprietary protocol version 1 and your patch introduces proprietary protocol version 2, that's a new driver.
Review the OpenStack dev mailing list post about his for more information.
Third Party CI Requirement Policy
See third party CI wiki.
Before you write any code
- Read the How To Contribute Page.
- Read the Cinder wiki page.
- Understand how Cinder works, what it's used for, why the other projects in OpenStack may or may not use it. Fully understand the difference between ephemeral storage on the Nova side versus the persistent storage offered by Cinder
- Cinder offers a reference implementation that should be used as a model. The reference implementation driver file is cinder/volume/drivers/lvm.py, not to be mistaken for cinder/volume/driver.py which is the base class that all of the drivers inherit from. Note that there are a lot of options that show up there regarding iSCSI targets etc, but this gives you an idea of the expectations in terms of features that are implemented and some of the behaviors. I strongly recommend loading up devstack (you're going to need it to test your driver anyway) and play around with the default LVM. It's really important that you get a feel for how Cinder works and interacts with the other OpenStack projects before you get too far along.
- You don't need a cinder spec for most drivers. You always need to submit a blueprint in Launchpad introducing your driver, so that it can be targeted for a release.
- We have a development channel on freenode: #openstack-cinder. There are developers here round the clock, it's a great resource for you get started. Log in, ask questions, don't stare at code in isolation for a week... if you're stuck on something just ask. There's also no need to start off with "Can I ask a question"... you likely won't get a response. Just type in your question, that way anybody monitoring the channel that might know the answer can step in and answer.
- You must implement all of the methods that exist as core features.
- Your driver should not make any state changes. (e.g. make Cinder database calls). The volume manager is responsible for making state changes after the driver is done talking to the storage backend.
- Unit tests for new code are required. We're in the process of converting everything to use mock (rather than mox) for our unit tests. Be sure when writing unit tests and setting up fakes to use mock, examples of it's usage can be found in the existing tests like cinder/tests/test_volume.py.
- Make sure you're not duplicating a configuration option that already exists. To verify this, you'll need to need look at the cinder/etc/cinder.conf.sample file. To generate this file:
- Install tox
- Run tox -egenconfig
- Make sure to follow the OpenStack Style Guide. Very likely you'll get nit pick reviews otherwise, which is not productive either way.
Submitting Driver For Review
- Do NOT bother the Cinder core team for reviews. We are aware of your patch being posted.
- Make sure your commit message follows the OpenStack project guidelines.
- Make sure your driver has appropriate third party testing done.
After Your Driver Is Added
Congratulations! You're not done yet though. After your driver has been merged there are still some things that need to be done.
- Make sure there is documentation for your driver
- Read and understand third party driver docs and work with OpenStack-Manuals on any concerns
- Continue to be available on IRC and attend the weekly meetings in case questions come up.
- Watch https://bugs.launchpad.net/openstack/cinder/+bugs for bugs with your driver.