Changes to BMO-Phabricator integration

[Mark Côté]

To reduce confusion and a growing maintenance burden, the Engineering
Workflow team plans to remove two pieces of Phabricator-Bugzilla
integration:


1.

The setting of r+ flags on the stub attachments in that link to
Phabricator revisions (
https://bugzilla.mozilla.org/show_bug.cgi?id=1490687).
2.

The Phabricator table in Bugzilla’s “My Requests” page (
https://bugzilla.mozilla.org/show_bug.cgi?id=1487422).


We plan on adding one more piece of integration: a panel on bug views
(show_bug.cgi) that shows the status of Phabricator revisions in
Phabricator’s terms, similar to the old MozReview table (
https://bugzilla.mozilla.org/show_bug.cgi?id=1489706).

The “stub attachments” will remain for the time being in order to
facilitate tracking non-review attachment flags (checkin-needed, etc).

# Rationale and background

There have been a lot of questions about our decisions surrounding
Bugzilla–Phabricator integration. We’ve expounded on those in various
threads over the last year and a half, but I will try to go into more
specifics.

At the start of the Phabricator project, having learned a lot from
MozReview, we consciously decided to limit the amount of integration to
Bugzilla. This not only reduces upfront costs and maintenance burden but
also avoids the complexity and ambiguity inherent in mixing two different
systems together. Aside from necessary linkages like authentication,
accounts, and security groups, the only other integration we implemented
was the setting of r+ statuses on stub attachments and, later, adding
Phabricator requests to BMO’s “My Dashboard”.

Unfortunately both of these have had bugs and caused confusion. Since
comments aren’t mirrored, the plain r+s were sometimes misleading if the
revisions (or Phabricator’s email notifications) weren’t also consulted
before landing. The requests view on “My Dashboard” suffered from bugs that
resulted in missing requests and was further impacted by our experiments
with reviewer groups that have no real analog in Bugzilla.

# Differing models

The central problem is that the models behind the two systems—Bugzilla’s
attachments and flags, Phabricator’s revisions and reviews—are very
different. Phabricator’s revisions have a much richer and more complex set
of metadata than Bugzilla attachments. It is essentially impossible to
represent Phabricator states as Bugzilla flags while preserving anything
close to the expected semantics of the latter; consulting Phabricator would
often be needed to make sense of any translated representation in Bugzilla.
Further, Phabricator’s model is also subject to changes and additions (for
example, the draft revision state, which is still being modified), which
creates additional fragility and maintenance burden. Finally, not all the
details we need are even exposed through APIs, in part because they are in
flux.

# Adding revision statuses to bugs

That said, we realize that seeing at a glance the state of revisions
associated with a given bug is very useful. We are building support into
Bugzilla to view revision data without translation into Bugzilla’s terms to
avoid any confusion as to the true state of revisions.

While we could also dump data from Phabricator’s dashboard into Bugzilla’s
“My Dashboard”, it would be much more work and more difficult to maintain,
since Phabricator’s dashboard itself is being updated. Furthermore, as all
code reviews are transitioned to Phabricator, the importance of this
dashboard will grow, and the number of requests in Bugzilla will shrink.
Thus relying on Phabricator to do what it does best is the better solution
for the future.

# Acknowledging difficulties

We are aware that splitting code review out into a separate system is a
huge change. We realize that, with our new tools and the decisions we have
made around integration, we are asking you to change your workflows by
setting up different email rules, looking in different places for the data
you need, communicating with other Mozillians in different ways, and
perhaps even establishing new practices and norms around code review. It
will take time to adapt. However we are already seeing benefits in terms of
automation that we haven’t previously been able to do (just one example: a
user set up Herald rules to notify of changes that impact localization),
and we will continue to build on this framework to accomplish goals that
have been talked about for many years. Allowing the tools to do what they
are best at lets us focus on new functionality, including suggested
reviewers, Try support for Lando, Lando notifications, fully automated
landings, and other items on our road map (
https://wiki.mozilla.org/Engineering_Workflow/Road_Map).

We appreciate your feedback and support as we work to improve the tools you
use every day.

Mark

[Ehsan Akhgari]

Hi everyone,

As someone who cares a lot about code review (both as a developer and as a
reviewer), I care a lot about the tools I work with and the workflows I’ve
built around them over the years. I’m sure I’m not the only one there.

What Mark wrote about below brings changes to some parts of our code review
workflows and I think it’s fair to assume that some people will find the
change unpleasant. I think it’s important to know that decisions like this
aren’t made lightly though, and the team working on Phabricator has looked
into making this integration work as much as possible, before coming to
this final conclusion.

What I’ve learned from the experience of the folks who worked closely on
this project over the past 3-4 years is that integrating an existing code
review system with an existing issue management system is an extremely
difficult task. There are certainly huge benefits to be reaped if a tight
integration is achieved, but there are great costs to also consider, and
the trade-off is tricky to get right.

As much as deep down in my heart, I secretly wish nothing would ever change
so that I could hold on to my old habits until who-knows-when, I realize
that sometimes it’s prudent to do what’s hard -- shaking off old habits and
workflows and pick up new ones, in the interest of the greater good.

In this case, even with my reviewer hat on, I think it would certainly be a
mistake for us to have tried as hard as we did for MozReview to integrate
BMO and Phabricator together at the expense of holding back the deployment
of Phabricator and new features in it. If our smart engineers working on
this hard problem have looked at this integration issue, have tried to make
it work, and have decided down the line that it’s best to correct course,
my hunch is to trust them and consider maybe it’s time to change some of my
old habits on how I interact with code reviews on Bugzilla.

Thanks,
Ehsan

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--
Ehsan

[Mark Côté]

(apologies: this was sent out to firefox-dev and dev.platform yesterday but
for some reason appears not to have made it to the latter)

To reduce confusion and a growing maintenance burden, the Engineering
Workflow team plans to remove two pieces of Phabricator-Bugzilla
integration:


1.

The setting of r+ flags on the stub attachments in that link to
Phabricator revisions (https://bugzilla.mozilla.org/
show_bug.cgi?id=1490687).
2.

The Phabricator table in Bugzilla’s “My Requests” page (
https://bugzilla.mozilla.org/show_bug.cgi?id=1487422

<https://bugzilla.mozilla.org/show_bug.cgi?id=1487422>).