Re: [xwiki-devs] [Proposal] GitHub code reviews and protected branches

Hi, Very interesting discussion. Not much to add to what was already said. I have always questioned the fact that we keep the master branch as the main development branch and it is very easy for someone new to clone it at the wrong time (i.e. when the build is failing) and get confused fast. Most github projects I see use the master branch as a stable-development branch to which they merge reviewed code or code from other active-development branch(es). Side note: One really nice feature that I would like to see on GitHub would be the ability to review already pushed commits (i.e. a "post-mortem" review). You would then have a nice overview of code that was *never* reviewed by anyone and could easily develop a workflow that tolerates direct pushes, but requires that even they are eventually reviewed (possibly with some Review Percentage Coverage minimum limit). I`m not sure I`m such a big fan of PR-only commits. Ultimately, I think I would even be in favor of getting your code in faster and fixing/reverting in case of problems (i.e. the opposite direction) instead of raising even more barriers in front of the contribution/commit. General question about building-checking each PR: If PR1 is built by CI automatically and is marked as PASSED, but commit A is pushed into master and it would make PR1 now fail the build, is PR1 re-built after commit A is pushed to master? If so, does it mean that each commit to master also triggers a rebuild of all the N PRs waiting for review to make sure they are not broken? AFAIU, this is the way things should work, however, given the elegant behemoth that XWiki has become, the build times and the stress on the CI infrastructure would IMO kill any fun and joy of developing and actually making a change in the project. I`m all for Code Reviews and a system that improves the current state where nobody is really responsible with it and, if it happens, it is generally done by the same few people. The way I imagine the perfect review system is one where each commit and each PR gets a reviewer automatically assigned from the organization (other than the author, ofc). PRs are blocked by the reviewer's approval and direct commits should (maybe/somehow?) be blocked by a Review Coverage Threshold, similar to the TPC at build time. I believe that if we could achieve this, it would invalidate the need for more complex branch/fork management and other formalities. With a bit of an effort and maybe GitHub API magic, I believe it could even be achievable to a certain extent. As you`ve said, the ultimate goal is for people to see the code and avoid finding things introduced 7 years ago that nobody *ever* had a second look at. Hope this helps, somehow :) -Eduard On Tue, May 23, 2017 at 9:05 AM, Sergiu Dumitriu <sergiu(a)xwiki.org> wrote: > Hi Vincent, > > On 05/17/2017 09:30 AM, Vincent Massol wrote: > > Hi Sergiu, > > > >> On 16 May 2017, at 07:36, Sergiu Dumitriu <sergiu(a)xwiki.org> wrote: > >> > >> Hi devs, > >> > >> A while ago GitHub introduced several features that I think can help > >> boost even more the code quality, reduce the bus factor, and make it > >> more attractive to contribute to the project. > >> > >> = Protected branches = > >> > >> Branches can be configured as protected in several ways: > >> * Require pull request reviews before merging > >> ** no direct commits are allowed, everything must go through a pull > request > >> ** a pull request must be reviewed by at least one other trusted > >> committer before it is allowed to be merged > >> > >> * Require status checks to pass before merging > >> ** pull requests must pass automated checks, for example by being > >> successfully built by a CI service > >> > >> * Restrict who can push to this branch > >> ** official branches (master + stable-x.y) could be restricted to > >> approved committers, but we could grant write access to all other > >> interested developers more easily > >> > >> > >> = Reviews for pull requests = > >> > >> Comments on all commits as well on pull requests have been supported > >> since the early days of GitHub, but more recently it is easier to submit > >> (and request) actual reviews for pull requests. Instead of simply > >> commenting, and changing that special field on Jira, an official pull > >> request status is supported, with three states: > >> > >> - review required > >> - changes requested > >> - approved > >> > >> PR authors can either await for reviews from anybody, or request someone > >> in particular for a review. > >> > >> Committers can filter PRs by their status, and they can also show only > >> the PRs that require their review. > >> > >> > >> = Getting more eyeballs on the code = > >> > >> As Linus' Law states, "given enough eyeballs, all bugs are shallow". > >> We've been experimenting with mandatory pull requests for a while in my > >> other XWiki-based project, with great success so far. So here's a > >> proposal for a different development workflow: > >> > >> 1. Set up 2 teams, one with master (senior) committers, fully vetted > >> committers that have proven they understand the XWiki code, as well as > >> the XWiki product, and one with junior committers > > > > How is that different from what we’re currently doing? > > > > Right now we have: > > * Committers (they’ve been voted committers because they have proven > their knowledge on our platform + long term dedication to the project). > They’re the “senior” of your team > > * Contributors, who need to go through PR to get their code in. They’re > the “juniors” of your other team. > > It's different because: > - they are part of the XWiki organization, not just some forkers; people > may care about the list of organizations that's displayed on their profile > - they can commit code in the official repository, so everybody else can > see their commits in one place (including through notification emails), > and every other committer can contribute to their branches > > >> 2. Protect the master branch. Require pull requests and reviews before > >> any code is merged in it. Restrict push only to the master committers. > > > > Main pros for me: > > * we can ask for the CI to pass before merging, thus disturbing less > other committers. > > * easier to converge for releases but *only* if we’re ready to drop > features. If we’re not then it’s the opposite and makes it harder to > converge. > > > > Main cons: > > * takes a LOT of time before code is merged. You can be sure that it’ll > need several hours before it gets merged and that you’ll have moved on to > something else when the comment comes in. And since your new work has an > important chance of being related you might end up chaining the PRs. > > > >> 3. Everybody works on separate branches > > > > How does the CI ensure that all branches are merged before the tests are > executed? > > Why all branches? I'm not sure I understand this... > > Jenkins has a GitHubPullRequestBuilder plugin, which can build every > pull request, after every new push to the PR branch, and this should say > if the build will work after merging that particular pull request. It > used to be fragile several years ago, but it's working great now. > > > Example: I’m working on something and I’m modifying some @Unstable API. > Someone else is working with the previous API. We’ll only discover the > issue late when both PRs are merged. > > There's nothing new, the same thing may happen with everybody committing > directly to master. Either there's a conflict, in which case the last > pull request to be merged will have to be rebased and reviewed manually, > or there's no conflict, but in this case how does committing to master > help detect the problem? Other than rebuilding the whole project every > time after every pull, in which case someone could be stuck indefinitely > in a push->failed->pull->build->repeat loop, as long as others keep > pushing while building. > > That's why the master auto-builds will stay in place, building each PR > separately isn't a replacement for the current quality check procedures, > but an enhancement. > > >> 4. Once the code is almost done, make a pull request and require reviews > >> from two junior committers > > > > Why from junior committers? > > For their learning, and so that senior committers don't have to waste > time with "this isn't our codestyle" reviews and low hanging bad-fruits. > > If the senior committer doesn't make the obvious mistakes, then the > review will be quick. Nobody is saying that every review will reveal at > least 5 serious problems, most reviews _should_ be quick and painless. > > > So you’d be asking junior devs to review senior devs’s code? How can > they do it and achieve it? While the junior may learn stuff, they’ll most > likely have no knowledge to do a proper review. > > That's why the seniors have to do a review as well. > > > FYI just had lunch with some Docker guys today who had this setup in > place. It was a nightmare and they had to drop it after a few months. Was > just too painful to ask for 2 reviews. They’re now down to 1 reviewer. > > The numbers are up for discussion, if you think two juniors plus a > senior is too much, we can go to one junior and one senior, or just one > senior if you really don't believe that early reviews from juniors have > no value. I for one saw how many mistakes I'd have missed were spotted > by other reviewers, and I'm spending less time doing trivial reviews. > > > How do you require reviews? > > It's a GitHub feature, when viewing a pull request there's a "Reviewers" > field where you can choose members of the project. Someone set as > reviewer will get an email notification, and they can also see which > pull request require their review. > > > How can you ensure they’ll have the time right now? It seems this would > be painful. > > Why right now? Will you rather have buggy code in master than wait a > while for someone else to review? > > Not every individual commit needs a separate pull request with its > reviews. If you work on something, then what you'll be working on next > depends on that something, maybe they belong together in the same pull > request? If it's a bugfix to something very recently developed, maybe it > would have been found by a review, in which case it should go in the > pull request that's already open. If it's a bugfix for an old bug, is it > that critical to have it in master in 2 minutes, since it's been > unresolved for a long time so far? > > It is painful, indeed, but "no pain, no gain". Is speed that much more > important that no speed impediments are worth a bit of extra quality? > > >> 4a. Or, instead of requesting, let committers volunteer themselves, but > >> it's less likely that someone will volunteer on time > >> 5. The junior committers must then carefully review the code, and either > >> require changes, just comment, or approve the pull request > >> 6. Once the junior committers have approved the pull request, the PR > >> author must request review from a senior committer > > > > wow … so 3 reviewers! > > Did I tell you that in PhenoTips we also usually require a review from > the QA team, which involves building from the branch, and manually > testing what the PR is fixing/improving/adding? > > >> 7. The senior committer can either approve and merge the pull request, > >> or send it back to step 3. > >> e. We can define allowed exceptions: don't require PRs from senior > >> committers if the fixes are really small and obvious, like fixing typos, > >> or small and important bugfixes that must be merged quickly, but these > >> should really be rare exceptions > >> > >> While it does sound like more work for an already overworked team, > > > > It’s a lot more work indeed. > > > >> this > >> has many benefits: > >> * the code will have better quality > >> * awareness of: > >> ** what's new / changing > >> ** how others are approaching a problem (especially juniors learning > >> from seniors by being exposed to more code) > >> ** the existing code, since the codebase is large and otherwise people > >> have few occasions to look at many of the parts of XWiki > >> * this means a larger bus factor for new code, and slowly increasing it > >> for existing code that's being touched by one and reviewed by many > >> * theoretically, less time spent doing reviews, since all committers > >> should look over every commit anyway, but this way they are explicitly > >> told when they should look, instead of wasting time reviewing work in > >> progress > > > > In theory I agree. In practice I have the feeling this means slowing > down the pace of development in favor of more shared knowledge. > > Aren't commits supposed to be reviewed anyway? See my last bullet above. > > > Personally I know that I cannot review any PR if I don’t understand what > the dev is doing and the code alone is almost never enough. I need to talk > to the person to understand the goal. Otherwise I just do cosmetic comments > which don’t help spread the knowledge. That’s unless it’s on a topic that I > completely master. > > Aren't new features supposed to be discussed before the implementation > starts? As I can see, there are design pages and ML discussions for > every major new feature, so this should ensure that every committer has > at least a general idea of what the goals are. > > As for talking with the dev to understand the goal, at PhenoTips we have > a weekly status meeting where we discuss what we're working on, so > everybody in the team knows what everybody else is working on. > > And these reviews are supposed to help everybody understand better what > everybody else is doing, so after a while you shouldn't have a problem > with not knowing what others are doing. > > And reviewers shouldn't be picked randomly, pick someone who is more > likely to know the domain. > > > Globally I have the feeling it would slow us down substantially (or it > doesn’t that it wouldn’t bring anything more at the expense of more > constraints). I like the idea of spreading the knowledge but I’m not sure > this would work for us. However, I like to try new stuff and decide based > on real feedback. > > > >> * larger community, since people can more quickly become junior > >> committers instead of having to invest many months of years of forkwork > >> before committership > > > > This I don’t understand. Contributors can already do PR so I don’t see a > difference (see my point above). Also this would mean defining on what new > rule you make someone a committer and the committership rules would > probably need to change (voting, etc). > > The difference is where the code is. Right now a non-committer can only > commit in a personal fork, which, as stated above: > > - other people can't write to, if they want to collaborate, unless > explicitly granted access to that fork > - doesn't send notifications when new commits are added > > Perhaps two examples will make it clearer why it's relevant: > > - For bigger features that take a while to be finished, sometimes the > original developer moves to a different task that's more urgent, and > someone else has to step in and take over the code. That wouldn't be > easy with a fork, but it's very simple when the code is in an "origin" > branch (even before the PR is ready to be opened) > - Sometimes it's easier for me to go and commit some changes directly > than to write in the pull request review what needs to be done, which > involves writing the code, copy-paste it to github, then the other > person copy-pastes from github to the IDE, then commits. > > > Also right now we have xwiki-contrib which is open to anyone in term of > committership and we’re pushing more and more to it so all this might not > be actually needed (except maybe on contrib if too many errors are > introduced by code that is not reviewed - I’m more worried about this than > for the xwiki repos TBH). > > > >> * easier collaboration on code, since it's very hard to work on someone > >> else's fork branches, but easy to work on an origin branch > >> > >> > >> So, what do you think? > > > > Sounds pretty ambitious to me :) > > > > The part that I prefer is the part about the CI building before merging > (see above) but even that is not so simple. Can we make dependent jobs also > build so that all tests are executed including functional tests in > xwiki-enterprise? > > > > I really don’t like the 3 reviews asked (even 2). One would already be a > lot IMO. It’d mean a lot of pinging around to find someone to review your > PR :) > > > > I’d be willing to try it out if others are interested but for a limited > amount of time based on these changes: > > * Same committership rules as now > > * Master is protected and all code needs to go through PR > > * Only 1 reviewer is required. This reviewer would do the merge. > > * The onus is on the committer to find a reviewer but everyone should > play the game. IMO that’s the hard part and we risk seeing always the same > person being asked to review. > > * We continue to do time-boxing for releases and we stop merging PRs 2 > days before the release. > > * We try this for 3 releases (i.e. 3 months - June-August) and then do a > postmortem to decide if we continue or not > > Sounds like a good start. > > > * We need to define some PR rules and reviewer "power". What if I > comment to an existing committer that they need to split their PR into > several ones so that I can understand it better? Would they be willing to > do that? What if the PR is good but could be better by following better > some coding style. Are we willing to annoy the committer and refuse the PR > for that reason? What if the PR has no tests? > > You can review a pull request commit-by-commit, if you find that easier, > and if the author made nice clean commits. > > The code rules should stay the same, there's already a requirement that > the TPC should only go up, not down, so if you don't like that tests are > missing, comment about that. The author can negotiate for an exception, > but that doesn't have anything to do with the fact that it's a pull > request: it's a commit like any other commit intended for the master > branch. If he would have done "frowned-upon things" directly on master, > would that be better or worse? > > > In conclusion I’m pretty sure this would slow down a lot and we’re > already a pretty small team. The real question is whether more knowledge > sharing and higher code quality is more important than pace of development > or not. It’s hard to decide on that (at least for me). > > The XWiki community prides in its transparency and democracy, and this > is a proposal up for discussion, let's hear more opinions. > > > Also I don’t like changing something for the sake of changing it. Are > there any recent experience that make you think that we need this change? > > No, nothing bad in XWiki, but: > - I haven't been monitoring commits in a long time, so I wouldn't have > noticed anything anyway > - I did commit some things on master that were not optimal, since I > haven't been keeping up to date with what else has been happening, so I > personally feel that my commits should be reviewed > - I have mostly good things to say about this workflow, which has been > in use for more than a year in the PhenoTips team > > Well, I should mention some stats: > > - Several PRs are merged within minutes, if they're small enough > - Most take one or two days to be merged > - If everybody is working hard to get their assignments done, PRs can > stay several days / couple of weeks before being reviewed, then comes a > period of reviews and merges > - Sometimes a big feature will be moved to the next cycle > - Pull requests that we're not happy with will stay open for several > months waiting for some free time to be refactored > > > In any case, thanks for starting this interesting topic. > > > > Thanks > > -Vincent > > > > -- > Sergiu Dumitriu > http://purl.org/net/sergiu/ >