1501416 - Update watchman for MozillaBuild

Status: RESOLVED FIXED

(Firefox Build System :: MozillaBuild, task)

Comment 1

[Ryan VanderMeulen [:RyanVM]]

Current upstream tip is hanging for me when I try to run |hg status|. Can you reproduce?

Comment 2

[Gregory Szorc [:gps]]

It seems to hang the first time I use it as well. But it works the 2nd time.

Looking at system calls using Process Monitor, it appears Python spawns watchman.exe, which does its own thing to start a background process. The thread Python spawns to manage the process exits. But the Python process stalls.

I suspect this is a "process group" issue with the way Mercurial/Python spawns watchman. I suspect watchman changed some process start flags for the child/background process it spawns and Mercurial/Python isn't properly "detaching."

This is either a bug in the way Mercurial is invoking watchman or a bug in watchman's process management. First step is to figure out what changed on watchman's end. The Facebook people should know what it will take to fix Mercurial, because they've likely done it internally without upstreaming the change :/

Comment 3

[wez]

Are you only experiencing this on Windows?  We are tracking an issue that manifests this way on Windows, and it is watchman specific (not mercurial), so I think it's fair if you open an issue on the watchman github tracker and concentrate things there.

Comment 4

[Ryan VanderMeulen [:RyanVM]]

Yes, this is on Windows.

Comment 5

[wez]

We've traced it to this commit https://github.com/facebook/watchman/commit/e5f393c0848ddbc19acd22ada2833d90a1728e9e so the theory is that initial connection is sitting in the queue of that one handle we never service :-p

We'll likely revert that for now and come up with a more robust solution; that commit was chiefly to reduce flakeyness in our CI system.

Comment 6

[Ryan VanderMeulen [:RyanVM]]

I'm not actively working on this and I'm not convinced it's worth doing at this point given the level of support for MozillaBuild.

Comment 8

[Ryan VanderMeulen [:RyanVM]]

This was done in the 3.4 release.