On Fri, Jun 2, 2017 at 3:30 AM, Paul Belanger <pabelan...@redhat.com> wrote:
> On Wed, May 24, 2017 at 04:04:20PM -0700, James E. Blair wrote: > > Hi, > > > > As part of Zuul v3, we're adding support for GitHub (and later possibly > > other systems). We want these systems to have access to the full power > > of cross-project-dependencies in the same way as Gerrit. However, the > > current syntax for the Depends-On footer is currently the > > Gerrit-specific change-id. > > > > We chose this in an attempt to be future-compatible with some proposed > > changes to Gerrit itself to support cross-project dependencies. Since > > then, Gerrit has gone in a different direction on this subject, so I no > > longer think we should weigh that very heavily. > > > > While Gerrit change ids can be used to identify one or more changes > > within a Gerrit installation, there is no comparable identifier on > > GitHub, as pull request numbers are unique only within a project. > > > > The natural way to identify a GitHub pull request is with its URL. > > > > This can be used to identify Gerrit changes as well, and will likely be > > well supported by other systems. Therefore, I propose we support URLs > > as the content of the Depends-On footers for all systems. E.g.: > > > > Depends-On: https://review.openstack.org/12345 > > Depends-On: https://github.com/ansible/ansible/pull/12345 > > > Hopefully not to off-topic, would it also be possible to support the > reverse of > this? I know we've unofficially used the Needed-By footer for some > governance > patches. It has been helpful when looking at git logs to see the other > direction > dependency from time to time. > > Not a big deal if it is a no, just something that popped into my head when > reading this topic. > So at the moment if we're trying to figure out why something hasn't entered the gate we can see "oh it depends-on this other things". However if we do a need-by that becomes a lot less obvious. If we're logging how the changes/deps are queued/merged (as discussed in this thread) then I don't see why not. As it is though I'd probably recommend against it. Cheers, Josh > > > Similarly to the Gerrit change IDs, these identifiers are easily > > navigable within Gerrit (and Gertty), so that reviewers can traverse the > > dependency chain easily. > > > > One substantial aspect of this change is that it is more specific about > > projects and branches. A single Gerrit change ID can refer to more than > > one branch, and even more than one project. Zuul interprets this as > > "this change depends on *all* of the changes that match". Often times > > that is convenient, but sometimes it is not. Frequently users ask "how > > can I make this depend only on a change to master, not the backport of > > the change to stable?" and the answer is, "you can't". > > > > URLs have the advantage of allowing users to be specific as to which > > instances of a given change are actually required. If, indeed, a change > > depends on more than one, of course a user can still add multiple > > Depends-On headers, one for each. > > > > It is also easy for Zuul connections to determine whether a given URL is > > referring to a change on that system without actually needing to query > > it. A Zuul connected to several code review systems can easy determine > > which to ask for the change by examining the hostname. > > > > URLs do have two disadvantages compared to Gerrit change IDs: they can > > not be generated ahead of time, and they are not as easily found in > > offline git history. > > > > With Gerrit change IDs, we can write several local changes, and before > > pushing them to Gerrit, add Depends-On headers since the change id is > > generated locally. URLs are not known until the changes are pushed to > > Gerrit (or GitHub pull requests opened). So in some cases, editing of > > an already existing commit message may be required. However, the most > > common case of a simple dependency chain can still be easily created by > > pushing one change up at a time. > > > > Change IDs, by virtue of being in the commit message of the dependent as > > well as depending change, become part of the permanent history of the > > project, no longer tied to the code review system, once they merge. > > This is an important thing to consider for long-running projects. URLs > > are less suitable for this, since they acquire their context from > > contemporaneous servers. However, Gerrit does record the review URL in > > git notes, so while it's not as convenient, with some additional tooling > > it should be possible to follow dependency paths with only the git > > history. > > > > Of course, this is not a change we can make instantaneously -- the > > change IDs have a lot of inertia and developer muscle memory. And we > > don't want changes that have been in progress for a while to suddenly be > > broken with the switch to v3. So we will need to support both syntaxes > > for some time. > > > > We could, indeed, support both syntaxes indefinitely, but I believe it > > would be better to plan on deprecating the Gerrit change ID syntax with > > an eye to eventually removing it. I think that ultimately, the URL > > syntax for Depends-On is more intuitive to a new user, especially one > > that may end up being exposed to a Zuul which connects to multiple > > systems. Having a Gerrit change depend on a GitHub pull request (and > > vice versa) will be one of the most powerful features of Zuul v3, and > > the syntax for that should be approachable. > > > > In short, I think the value of consistency across multiple backends and > > ease of use for new users outweighs the small loss of functionality for > > Gerrit power users in this case. > > > > I propose we adopt support for URLs in all source drivers in v3, and > > declare Gerrit change IDs deprecated. We will continue to support both > > for a generous deprecation period (at least 6 months after the initial > > Zuul 3.0 release), and then remove support for them. > > > > How does that sound? > > > > -Jim > > > > _______________________________________________ > > OpenStack-Infra mailing list > > OpenStack-Infra@lists.openstack.org > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-infra > > _______________________________________________ > OpenStack-Infra mailing list > OpenStack-Infra@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-infra >
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