My impression is that we have two opposing schools of thought here: 1. Backport as little as possible, to avoid unforeseen consequences 2. Backport as much as proves practical, to eliminate bugs in supported versions
Do other people agree with this assessment? If so, how can we find common ground? One possible solution would be to leave the decision on backporting up to the committer, without specifying a project-wide policy. This seems to be the status quo, and would lead to some variation across committers regarding what types of fixes are backported. We could also choose to delegate the decision to the release manager; I favor leaving the decision with the committer, to eliminate the burden on release managers. Here's a thought: rather than defining a prescriptive "policy" that we expect committers to abide by, we could enumerate in the documentation the competing concerns that we expect committers to consider when making decisions on backports. The committing docs could read something like: "When bug fixes are committed to master, the committer should evaluate the fix to determine whether or not it should be backported to supported versions. This is left to the committer, but they are expected to weigh the following concerns when making the decision: - Every backported change comes with a risk of unintended consequences. The change should be carefully evaluated to ensure that such side-effects are highly unlikely. - As the complexity of applying a backport increases due to merge conflicts, the likelihood of unintended consequences also increases. Bug fixes which require extensive rebasing should only be backported when the bug is critical enough to warrant the risk. - Users of supported versions benefit greatly from the resolution of bugs in point releases. Thus, whenever concerns #1 and #2 can be allayed for a given bug fix, it should be backported." Cheers, Greg On Mon, Jul 16, 2018 at 3:06 AM, Alex Rukletsov <a...@mesosphere.com> wrote: > Back porting as little as possible is the ultimate goal for me. My reasons > are closely aligned with what Andrew wrote above. > > If we agree on this strategy, the next question is how to enforce it. My > intuition is that committers will lean towards back porting their patches > in arguable cases, because humans tend to overestimate the importance of > their personal work. Delegating the decision in such cases to a release > manager in my opinion will help us enforce the strategy of minimal number > backports. As a bonus, the release manager will have a much better > understanding of what's going on with the release, keyword: "more > ownership". > > On Sat, Jul 14, 2018 at 12:07 AM, Andrew Schwartzmeyer < > and...@schwartzmeyer.com> wrote: > >> I believe I fall somewhere between Alex and Ben. >> >> As for deciding what to backport or not, I lean toward Alex's view of >> backporting as little as possible (and agree with his criteria). My >> reasoning is that all changes can have unforeseen consequences, which I >> believe is something to be actively avoided in already released versions. >> The reason for backporting patches to fix regressions is the same as the >> reason to avoid backporting as much as possible: keep behavior consistent >> (and safe) within a release. With that as the goal of a branch in >> maintenance mode, it makes sense to fix regressions, and make exceptions to >> fix CVEs and other critical/blocking issues. >> >> As for who should decide what to backport, I lean toward Ben's view of >> the burden being on the committer. I don't think we should add more work >> for release managers, and I think the committer/shepherd obviously has the >> most understanding of the context around changes proposed for backport. >> >> Here's an example of a recent bugfix which I backported: >> https://reviews.apache.org/r/67587/ (for MESOS-3790) >> >> While normally I believe this change falls under "avoid due to unforeseen >> consequences," I made an exception as the bug was old, circa 2015, >> (indicating it had been an issue for others), and was causing recurring >> failures in testing. The fix itself was very small, meaning it was easier >> to evaluate for possible side effects, so I felt a little safer in that >> regard. The effect of not having the fix was a fatal and undesired crash, >> which furthermore left troublesome side effects on the system (you couldn't >> bring the agent back up). And lastly, a dependent project (DC/OS) wanted it >> in their next bump, which necessitated backporting to the release they were >> pulling in. >> >> I think in general we should backport only as necessary, and leave it on >> the committers to decide if backporting a particular change is necessary. >> >> >> On 07/13/2018 12:54 am, Alex Rukletsov wrote: >> >>> This is exactly where our views differ, Ben : ) >>> >>> Ideally, I would like a release manager to have more ownership and less >>> manual work. In my imagination, a release manager has more power and >>> control about dates, features, backports and everything that is related >>> to >>> "their" branch. I would also like us to back port as little as possible, >>> to >>> simplify testing and releasing patch versions. >>> >>> On Fri, Jul 13, 2018 at 1:17 AM, Benjamin Mahler <bmah...@apache.org> >>> wrote: >>> >>> +user, I probably it would be good to hear from users as well. >>>> >>>> Please see the original proposal as well as Alex's proposal and let us >>>> know >>>> your thoughts. >>>> >>>> To continue the discussion from where Alex left off: >>>> >>>> > Other bugs and significant improvements, e.g., performance, may be >>>> back >>>> ported, >>>> the release manager should ideally be the one who decides on this. >>>> >>>> I'm a little puzzled by this, why is the release manager involved? As we >>>> already document, backports occur when the bug is fixed, so this >>>> happens in >>>> the steady state of development, not at release time. The release >>>> manager >>>> only comes in at the time of the release itself, at which point all >>>> backports have already happened and the release manager handles the >>>> release >>>> process. Only blocker level issues can stop the release and while the >>>> release manager has a strong say, we should generally agree on what >>>> consists of a release blocking issue. >>>> >>>> Just to clarify my workflow, I generally backport every bug fix I commit >>>> that applies cleanly, right after I commit it to master (with the >>>> exceptions I listed below). >>>> >>>> On Thu, Jul 12, 2018 at 8:39 AM, Alex Rukletsov <a...@mesosphere.com> >>>> wrote: >>>> >>>> > I would like to back port as little as possible. I suggest the >>>> following >>>> > criteria: >>>> > >>>> > * By default, regressions are back ported to existing release >>>> branches. A >>>> > bug is considered a regression if the functionality is present in the >>>> > previous minor or patch version and is not affected by the bug there. >>>> > >>>> > * Critical and blocker issues, e.g., a CVE, can be back ported. >>>> > >>>> > * Other bugs and significant improvements, e.g., performance, may be >>>> back >>>> > ported, the release manager should ideally be the one who decides on >>>> this. >>>> > >>>> > On Thu, Jul 12, 2018 at 12:25 AM, Vinod Kone <vinodk...@apache.org> >>>> wrote: >>>> > >>>> > > Ben, thanks for the clarification. I'm in agreement with the points >>>> you >>>> > > made. >>>> > > >>>> > > Once we have consensus, would you mind updating the doc? >>>> > > >>>> > > On Wed, Jul 11, 2018 at 5:15 PM Benjamin Mahler <bmah...@apache.org >>>> > >>>> > > wrote: >>>> > > >>>> > > > I realized recently that we aren't all on the same page with >>>> > backporting. >>>> > > > We currently only document the following: >>>> > > > >>>> > > > "Typically the fix for an issue that is affecting supported >>>> releases >>>> > > lands >>>> > > > on the master branch and is then backported to the release >>>> branch(es). >>>> > In >>>> > > > rare cases, the fix might directly go into a release branch >>>> without >>>> > > landing >>>> > > > on master (e.g., fix / issue is not applicable to master)." [1] >>>> > > > >>>> > > > This leaves room for interpretation about what lies outside of >>>> > "typical". >>>> > > > Here's the simplest way I can explain what I stick to, and I'd >>>> like >>>> to >>>> > > hear >>>> > > > what others have in mind: >>>> > > > >>>> > > > * By default, bug fixes at any level should be backported to >>>> existing >>>> > > > release branches if it affects those releases. Especially >>>> important: >>>> > > > crashes, bugs in non-experimental features. >>>> > > > >>>> > > > * Exceptional cases that can omit backporting: difficult to >>>> backport >>>> > > fixes >>>> > > > (especially if the bugs are deemed of low priority), bugs in >>>> > experimental >>>> > > > features. >>>> > > > >>>> > > > * Exceptional non-bug cases that can be backported: performance >>>> > > > improvements. >>>> > > > >>>> > > > I realize that there is a ton of subtlety here (even in terms of >>>> which >>>> > > > things are defined as bugs). But I hope we can lay down a policy >>>> that >>>> > > gives >>>> > > > everyone the right mindset for common cases and then discuss >>>> corner >>>> > cases >>>> > > > on-demand in the future. >>>> > > > >>>> > > > [1] http://mesos.apache.org/documentation/latest/versioning/ >>>> > > > >>>> > > >>>> > >>>> >>>> >> >
