logging with MOZ_LOG on the try server


NB: This is mostly for my own public reference. I had written about this elsewhere in 2016 but when arriving at a similar problem, failed to reproduce this. You may skip the following section, if you're familiar the terminology in the title

what is MOZ_LOG?

MOZ_LOG is an environment variable Firefox developers can use to tell specific code sections to emit verbose (or very verbose) status messages for some if its inner workings. This is also called Gecko Logging.

what is the try server

The try server is a repository that allows you to submit code without actually checking it into the public repository. Pushes to try get run through all of our tests, which helps identifying problems and test failures before they are part of our code.

logging with MOZ_LOG on the try server

There is a test failure on Mac OS X, that I can hardly debug. As a first step, I'll push this to the try-server with more logging output enabled.

My test is a mochitest, so I modified testing/mochitest/runtests.py:

diff --git a/testing/mochitest/runtests.py b/testing/mochitest/runtests.py
index 45545b4..5afdffd 100644
--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -91,7 +91,7 @@ here = os.path.abspath(os.path.dirname(__file__))
 # Try run will then put a download link for all log files
 # on tbpl.mozilla.org.

-MOZ_LOG = ""
+MOZ_LOG = "nsDocShellLogger:4,CSPParser:4,CSPUtils:4,CSPContext:4,CSP:4"

And now we play the waiting game.

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