Starting from DRBD kernel module version 9.0.20 we use spatch to generate compatibility patches that are required to build the kernel module on a host machine. Older kernels need different and more patches than new ones as we try to use latest Linux upstream features as our base line in DRBD.
While using spatch makes maintenance a lot easier, it slightly complicates things for users just trying to
compile one of our release-tarballs on their machine.
Our tarballs ship with a wide range of pre-generated patches, but we can never build for everybody (e.g., locally patched kernels, distribution kernels of distributions we don't build for in the first place,...).
Additionally, spatch is a beast on its own. As of now we require a very current version that is not packaged
in any distribution, and even if, we actually don't like to force a ton of OCaml dependencies on everybody
trying to build a release-tarball.
This is where saas comes into the picture. It is a web service, hosted by LINBIT,
that takes as input a "DRBD tarball version", and a "compat.h" (which describes the capabilities of your
kernel). From that, it generates a patch with spatch, and returns it.
For the regular user, this is handled transparently by our Makefiles. A manual call looks similar to this:
curl -d "$(cat compat.h | base64 -)" -X POST http://localhost:8080/api/v1/spatch/9.0.20-0rc2