[llvm-dev] [cfe-dev] [RFC] Deprecate email code reviews in favor of Phabricator

Wed May 5 12:59:50 PDT 2021

On Wed, May 5, 2021 at 4:21 AM Aaron Ballman <aaron at aaronballman.com> wrote:

> On Tue, May 4, 2021 at 8:35 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
> >
> >
> >
> > On Tue, May 4, 2021 at 4:24 AM Aaron Ballman via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
> >>
> >> On Mon, May 3, 2021 at 1:24 PM Krzysztof Parzyszek via cfe-dev
> >> <cfe-dev at lists.llvm.org> wrote:
> >> >
> >> > Statement:
> >> >
> >> > Our current code review policy states[1]:
> >> >
> >> > “Code reviews are conducted, in order of preference, on our web-based
> code-review tool (see Code Reviews with Phabricator), by email on the
> relevant project’s commit mailing list, on the project’s development list,
> or on the bug tracker.”
> >> >
> >> > This proposal is to limit code reviews only to Phabricator.  This
> would apply to all projects in the LLVM monorepo.  With the change in
> effect, the amended policy would read:
> >> >
> >> > “Code reviews are conducted on our web-based code-review tool (see
> Code Reviews with Phabricator).”
> >>
> >> Personally, I am in favor of this policy for initiating code reviews,
> >> but am opposed to it for post-commit feedback. The problem, as I see
> >> it, is that not every change *gets* code review via Phab and the email
> >> lists are the only place on which to provide that post-commit
> >> feedback. This largely comes up in two ways: NFC changes and changes
> >> made by code owners in the area of the compiler which they own. We
> >> still need *some* mechanism by which to provide them post-commit
> >> feedback. Currently, the way we provide that is frequently via an
> >> email reply to the commit message on the *-commits list so that the
> >> issue can be seen by both the patch author and the community at large.
> >>
> >> > Current situation:
> >> >
> >> > In a recent llvm-dev thread[2], Christian Kühnel pointed out that
> pre-commit code reviews rarely originate via an email (most are started on
> Phabricator), although, as others pointed out, email responses to an
> ongoing review are not uncommon.  (That thread also contains examples of
> mishaps related to the email-Phabricator interactions, or email handling
> itself.)
> >> > I don’t have specific information about post-commit reviews.  It
> seems like the most common form is an email reply to the auto-generated
> commit message, although (in my personal experience), “raising a concern”
> in the commit on Phabricator or commenting in the pre-commit review is
> usually sufficient to get author’s attention.
> >> > We have Phabricator patches that automatically apply email comments
> to the Phabricator reviews, although reportedly this functionality is not
> fully reliable[3,4].  This can cause review comments to be lost in the
> email traffic.
> >> >
> >> >
> >> >
> >> > Benefits:
> >> >
> >> > Single way of doing code reviews: code reviews are a key part of the
> development process, and having one way of performing them would make the
> process clearer and unambiguous.
> >> > Review authors and reviewers would only need to monitor one source of
> comments without the fear that a review comment may end up overlooked.
> >> > Local Phabricator extensions would no longer be needed.
> >> >
> >> >
> >> >
> >> > Concerns:
> >> >
> >> > For post-commit reviews, the commenter would need to find either the
> original review, or the Phabricator commit (e.g.
> https://reviews.llvm.org/rG06234f758e19).  Those are communicated
> (perhaps ironically) via email, which implies that those automatic emails
> should remain in place.
> >>
> >> The Phab commit message does not have any subscribers though, and so
> >> my understanding is that comments on that Phab interface are not
> >> communicated out to the community as a whole, which means the
> >> community may miss out on important post-commit-review information
> >> like general awareness of the problem, workarounds people can use
> >> until the author corrects something, alternative ideas on how to fix
> >> the issue, etc. Or do I misunderstand the way Phab works in this
> >> workflow?
> >>
> >> Also, "the commenter would need to find the Phabricator commit"
> >> concerns me -- adding extra burden on the people providing feedback
> >> means that *some* amount of those people will struggle enough to
> >> simply not provide that feedback. Responding to an email is about as
> >> low as I think we can set that bar, so the current approach has better
> >> ergonomics for giving feedback. When I look at an existing NFC commit
> >> email (
> https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20210503/368413.html
> ),
> >> I don't see any direct link back to the Phabricator commit, so I have
> >> to know to get the hash and try using that with an
> >> https://reviews.llvm.org/rG in front of it.
> >
> >
> > This is a simple problem to solve by fixing the format of the emails
> that are sent, I believe we have control over this right now. We could:
> >
> > - add the https://reviews.llvm.org/rG<hash> to every email, and not to
> GitHub.
> > - make sure that the lists are subscribed on the commits on Phab so that
> notifications are generated to the list on post-commit feedback.
> >
> >>
> >> None of the existing links
> >> in the email get me to where I'd need to go to add my review feedback,
> >> but hitting the Reply button in my mail client will work. Adding a
> >> third link and telling people "click on the link in the email" means
> >> they've got a 50/50 shot of getting the right link because one of the
> >> links goes to GitHub where you can also add comments.
> >>
> >> > The current policy has been in place for a long time and it’s
> expected that some people will continue using email for reviews out of
> habit or due to lack of awareness of the policy change.
> >> > Because of the larger variety, email clients may offer better
> accessibility options than web browsers.
> >> >
> >> >
> >> >
> >> > Potential future direction:
> >> >
> >> > This section presents a potential future evolution of the review
> process.  Christian has conducted experiments suggesting that we can
> replace the XXX-commits mailing lists with notifications directly from
> Phabricator:
> >> >
> >> > For each of the mailing lists, we create a "project" with the same
> name in Phabricator, e.g. [5]. Every Phabricator user can join/leave these
> projects on their own.
> >> > Everyone on these projects will receive the same email notifications
> from Phabricator as we have on the mailing lists. This is configured via
> "Herald" rules in Phabricator, as today, e.g. [7].
> >>
> >> Tangential complaint -- our use of Herald causes some pain for me as a
> >> list moderator because we've reached the point where Herald
> >> automatically adds so many subscribers to a review that it gets marked
> >> as spam for every email that is generated for the review. It's to the
> >> point on cfe-dev where over half of the moderated emails are
> >> consistently not spam some weeks.
> >
> >
> > I'm surprised that the reviews are going to cfe-dev@ and not
> cfe-commits@?
>
> Sorry, think-o on my part. I meant to say cfe-commits, not cfe-dev.
>
> > But also, I didn't know that the mailman instance had a spam filter: I
> thought this was based purely on whether the sender is subscribed (or
> whitelisted)?
>
> It also filters based on number of recipients on the message and the
> size of the message body (which occasionally gets tripped by
> legitimate reviews that have very large diffs).
>
> >> This delays the community receiving
> >> the information while the patch reviewers/subscribers continue to get
> >> it. In turn, this causes a problem where sometimes the people
> >> subscribed to the patch say something is OK and the patch lands before
> >> the community ever sees the review and has a chance to comment on it.
> >> I'm wary of suggestions that involve heavier use of Herald until we
> >> get that mailing list issue resolved.
> >>
> >> > Users can reply to these email notifications and Phabricator will
> incorporate these responses with their email client, see [6] for some
> example emails. Quoting and markup is supported as well.
> >> > We do NOT migrate the membership lists. Users need to sign up to the
> projects manually. We will send an email with instructions to the mailing
> lists once everything is set up.
> >> > The current XXX-commits mailing lists will be shut down
> >> > The timeline for the migration is to be defined.
> >>
> >> Given how often Phabricator goes down (which is not super often, but
> >> often enough that people know it happens),
> >
> > Data-driven: I am aware of two outages for the last entire year, and
> each lasted for < 1/2 day.
>
> According to my totally unscientific method of searching for
> "phabricator down" in my archived email, I see about 600 messages on
> the topic. This also includes scheduled downtime announcements,
> resumed service announcements, DNS mishaps local to people, and
> replies on threads so it's not meant to suggest Phab has gone down
> anywhere near 600 times. However, the kind of issues I am worried
> about are ones where Phabricator would give exceptions (as in
> https://lists.llvm.org/pipermail/llvm-dev/2020-June/142836.html).
>

Until last June when I took over the instance, there was a known issue
which caused the outage you're referring to very frequently. In particular
the system root partition was too small and not resizeable and the system
logs were filling the disk in O(weeks), faster than the log rotation would
delete them. In such cases MySQL would stop responding.
So for a while we were just manually cleaning the logs and rebooting the
instance when it happens. But I upgraded all this (looking at my archive,
it was on 7/5/2020) and it held pretty well on the new system I believe.
We also have continuous monitoring right now, which checks for Phab
availability and notify us by email, so such issues don't go unnoticed, see
the metric (which measured our previous outage from 4/14-15 which was
reported on llvm-dev@):

[image: Screen Shot 2021-05-05 at 12.55.56 PM.png]

I also just got this morning the alert on Mysql Disk partition being above
85% disk space utilization, so I'll likely grow this next weekend in
anticipation! :)

-- 
Mehdi

>
> ~Aaron
>
> >
> >
> >
> >>
> >> I am deeply uncomfortable
> >> with the idea of shutting down the current *-commits mailing lists
> >> because of the chance for data loss. Personally, I think the *-commits
> >> lists are working well and I would prefer they be left alone.
> >>
> >> ~Aaron
> >>
> >> >
> >> > For experimenting, feel free to sign up to the prototype project at
> [5] . This project receives all commit and code review notifications.
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > [1]
> https://llvm.org/docs/CodeReview.html#what-tools-are-used-for-code-review
> >> >
> >> > [2] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150129.html
> >> >
> >> > [3] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150136.html
> >> >
> >> > [4] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150139.html
> >> >
> >> > [5] https://reviews.llvm.org/project/view/104/
> >> >
> >> > [6] https://reviews.llvm.org/D101432
> >> >
> >> > [7] https://reviews.llvm.org/H769
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> >
> >> > Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > cfe-dev mailing list
> >> > cfe-dev at lists.llvm.org
> >> > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >> _______________________________________________
> >> cfe-dev mailing list
> >> cfe-dev at lists.llvm.org
> >> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
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