I can see a hang in `startServers()` specifically in `MochitestServer.ensureReady()` when the "server_alive.txt" file cannot be created by Mochitest server component: https://dxr.mozilla.org/mozilla-central/rev/cfe6399e142c71966ef58a16cfd52c0b46dc6b1e/testing/mochitest/runtests.py#492-506 https://dxr.mozilla.org/mozilla-central/rev/cfe6399e142c71966ef58a16cfd52c0b46dc6b1e/testing/mochitest/server.js#177-184 This happens when a profile path has been specified with eg. a Unicode character in the Mochitest harness, and `serverAlive.exists()` returns false. Given that there is no else block with a proper failure message, the harness just times out.

Actually we cannot get rid of the hang in such a situation but we can at least provide a Javascript error which then can be picked up by Treeherder for the error line. The underlying problem here is in xpcshell which is covered via bug 1453647.

Comment on attachment 8967346 [details] Bug 1453596 - [mochitest] Throw errors instead of strings to get line numbers. https://reviewboard.mozilla.org/r/236044/#review241836

Comment on attachment 8967345 [details] Bug 1453596 - [mochitest] Throw exception if path for server alive file doesn't exist. https://reviewboard.mozilla.org/r/236042/#review241842 ::: testing/mochitest/server.js:176 (Diff revision 1) > } else { > serverAlive.initWithPath(_PROFILE_PATH); > } > > // If we're running outside of the test harness, there might > // not be a test profile directory present This comment seems a little misleading - maybe worth updating, or just deleting the comment?

Comment on attachment 8967345 [details] Bug 1453596 - [mochitest] Throw exception if path for server alive file doesn't exist. https://reviewboard.mozilla.org/r/236042/#review241842 > This comment seems a little misleading - maybe worth updating, or just deleting the comment? Misleading in which sense? Mochitest for example sets the _PROFILE_PATH, which might then not be present.

I think the comment makes it sound like server.js does not always expect the directory to be present -- as though it is okay for the directory not to exist. But actually, if the directory does not exist, we will throw an error (now). Maybe that's just my interpretation.

I see. I will update the commit.

Pushed by hskupin@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/14d208836dd3 [mochitest] Throw exception if path for server alive file doesn't exist. r=gbrown https://hg.mozilla.org/integration/autoland/rev/e67b96dc309c [mochitest] Throw errors instead of strings to get line numbers. r=gbrown

https://hg.mozilla.org/mozilla-central/rev/14d208836dd3 https://hg.mozilla.org/mozilla-central/rev/e67b96dc309c

Stability improvements for mochitest which would be good to see uplifted to mozilla-beta.

https://hg.mozilla.org/releases/mozilla-beta/rev/6bfef70fa570 https://hg.mozilla.org/releases/mozilla-beta/rev/1e47c5ece1f2