X-Wikimedia-Debug, your new secret side-kick - Wikitech-l

31 Mar 2016

Hey all,

I'm writing to let you know of a cool new facility for debugging MediaWiki
code on the Wikimedia production cluster -- the X-Wikimedia-Debug
<https://wikitech.wikimedia.org/wiki/X-Wikimedia-Debug> HTTP header.

By setting this header on requests to Wikimedia wikis, you can:

- Bypass the cache.
- Force Varnish to pass your request to a specific backend server.
- Profile request and log profiling data to XHGui.
- Turn on all log channels and send log messages to a special view in
Kibana / Logstash.
- Force MediaWiki to process the request in read-only mode.

And the best part: there are browser extensions for Chrome and Firefox that
provide a friendly user-interface for these features:

http://i.imgur.com/XzWUk0h.gifv

http://i.imgur.com/lJ7l6Vl.gifv

Cool? Cool.

Read the docs on Wikitech
<https://wikitech.wikimedia.org/wiki/X-Wikimedia-Debug> for more
information.