What is Freshmaker?

Freshmaker is a service which:

• Rebuilds various artifacts after its dependencies changed. For example:
  • Rebuilds module when .spec file of RPM in a module is updated or the RPM is pushed to stable using Bodhi.
  • Rebuilds container image when RPM in a container is updated or pushed to stable using Bodhi.
  • ...
• Provides a REST API to retrieve information about artifact rebuilds and the reasons for these rebuilds and sends messages to the message bus about these event.
• Is based on Event-Handler architecture:
  • Events are fedmsg messages received from other services like dist-git, Koji, Bodhi, ...
  • Handlers are small classes using the high-level API provided to them by Freshmaker core to rebuild artifacts.
• Provides high-level API to track dependencies between artifacts and make rebuilding of them easy.

How does it work?

Freshmaker waits for new fedmsg messages about artifact being updated, this happens in consumer.py. Every fedmsg message handled by a Freshmaker is parsed by one of the parsers which can be found in the parsers directory. This parser converts the fedmsg to Event object (inherits from BaseEvent). All the events are defined in the events.py.

This Event object is then handled by one or more handlers defined in the handlers directory.

The handlers typically do following:

• Find out the list of artifacts like RPMs, Container images, ... which must be rebuilt as result of Event.
  • There are built-in classes to find these information in PDC or Lightblue.
• Plan the rebuild of artifacts and store them in Freshmaker database in tree-like structure.
  • Artifacts can depend on each other and Freshmaker ensures they are built in the right order.
• Prepare the prerequisites for a rebuild.
  • This can for example mean generating RPM repository with updated packages using ODCS.
• Start the rebuild.

Most of the common tasks for handlers are already implemented in Freshmaker including:

• Database and methods to store artifacts, their dependencies and all the information to build them there.
• Classes to get the information about artifacts from Koji, Lightblue, PDC, MBS, ...
• Classes to start the builds in Koji, ODCS, MBS, ...

The handler which rebuilds all the modules after the .spec file of RPM including in a module is updated can look like this:

class RebuildImagesOnGitRPMSpecChange(BaseHandler):
    name = "RebuildImagesOnGitRPMSpecChange"

    def can_handle(self, event):
        return isinstance(event, GitRPMSpecChangeEvent)

    def handle(self, event):
        # Get the list of modules with this package from this branch using PDC.
        pdc = PDC(conf)
        modules = pdc.get_latest_modules(component_name=event.rpm,
                                        component_branch=event.branch,
                                        active='true')

        for module in modules:
            name = module['variant_name']
            version = module['variant_version']

            # Check if Freshmaker is configured to rebuild this module.
            if not self.allow_build(ArtifactType.MODULE, name=name, version=version):
                continue

            # To rebuild a module, we need to bump its release in dist-git repo.
            commit_msg = "Bump to rebuild because of %s rpm spec update (%s)." % (event.rpm, event.rev)
            rev = utils.bump_distgit_repo('modules', name, branch=version, commit_msg=commit_msg, logger=log)

            # We start the rebuild of a module and store it in Freshmkaer DB.
            build_id = self.build_module(name, version, rev)
            if build_id is not None:
                self.record_build(event, name, ArtifactType.MODULE, build_id)