github, restructuring and versioning
Jay Shaughnessy
jshaughn at redhat.com
Thu Mar 7 17:01:58 UTC 2013
Starting a new thread to consolidate some thoughts in the other two
threads...
After reading through the github migration threads and wiki, I see it
actually involves a few different things:
- The actual migration.
- Proposed pull-request workflows.
- The split to multiple repositories.
- Versioning schemes.
The actual migration plan is detailed and Heiko looks to have done a
good job of mapping out the details of how it will happen, including a
dry-run.
The new workflows look promising, especially from a code-review
perspective. I think we'll need that written up more formally for
ourselves and contributors. And maybe have a good demo for the team so
people (like me) get a good grasp of what we'll be doing. These
processes are also something we can modify as we go.
I'm OK with the idea of breaking RHQ into 3 pieces, core, plugins, and
helpers. I think it will be helpful to plugin developers to potentially
work with a smaller codebase, and a clearly identified helper project.
I also think the decision to avoid further granularity is a good one.
We will need to add some Jenkins jobs, but I don't think it will be an
unmanageable number (it's not 3 times the number we have today). And we
will likely need to update our release processes, again. Keeping the
platform plugin in core makes sense so that core can actually run on its
own, and also for anyone that plans to use only custom plugins.
It's the proposed dependency versioning that I'm questioning.
I'm not convinced there is real benefit to plugin writers or
contributors by having rhq-plugins/master depend on a released version
of rhq-core. In short, what's wrong with instead asking the developer to
git checkout rhq-plugins/release-X rather than rhq-plugins/master?
A plugin developer does not need to build rhq-plugins/master to develop
a new plugin. On the other hand, rhq-helpers/master, plugin-gen in
particular, would benefit from depending on released artifacts. In that
case the plugin dev could build the generator easily, against deps
published in central, and run a real server/agent of the same version,
installed from product dists.
As for working on an existing plugin; an enhancement or bug fix could be
built against rhq-plugins/release-X. Rhq-plugins/release-X is easily
built against central. The feature or fix would be compatible with the
published version of core.
Using 4.6 as an example, if we had an rhq-plugins/release-4.6 branch, a
developer could opt to build this branch against the published
artifacts, and make a fix or enhancement to the 4.6 plugin. Work
committed here could be cherry-picked to master as needed. If in fact
the developer or contributor elected to work with master they certainly
could, in the same manner as today, by building rhq-core/master and
working with the snapshot version.
As a further example, let's say someone finds a bug in the 4.6 AS7
plugin. It could be fixed against rhq-plugins/release-4.6 by anyone,
without having to build core. It could also be fixed in
rhq-plugins/master with a full dev environment, and cherry-picked back.
And rhq-plugins-4.6.1 could be released without a need to release a new
core/server.
The current proposal on the wiki is to have rhq-plugins/master depend on
rhq-core's current release version, and not on rhq-core/master's
snapshot version. This will certainly make development more difficult.
One immediate example will be the new provisioning implementation. This
feature development will involve new facets, change to the plugin
descriptor, and introduce other dependencies between plugin code and the
[core] container. A strategy that forces the plugin code to conform to
rhq-core's release version will make this very hard.
Let's talk a bit about plugin/core compatibility. As it stands today (I
believe) an agent plugin can be dropped into an RHQ server, and we don't
really validate it, we assume that it is compatible. Assuming the plugin
descriptor parses, and metadata updates succeed, we're good on the
server and the agent is free to pull it down. It's pretty loose. That
doesn't really have to change. Plugin release cadence is not really
dependent on rhq-server version. It simply has to be compatible.
Developing against a release version will give you that and (unless
using deprecated features that are going away) will give you
compatibility with the next release. But, to ensure timely release of a
plugin leveraging new features of core, it must be easily developed
against core's snapshot version. To prevent this will make things
difficult, likely force unnecessary core releases, and create lag times
between core and plugin releases.
The benefit of being able to check out and build rhq-plugins/master
without needing to also build rhq-core/master, does not seem to be
enough to merit the downside to plugin development and release.
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