Since at 2013-04-05 04:29:46 UTC, Zuul no more receives events from Gerrit. It uses a CLI command such as:
ssh -p 29418 jenkins-bot@manganese.wikimedia.org gerrit stream-events
I did stream-events using both the jenkins-bot user and my own account 'hashar'. While submitting a new patchset or posting a comment: nothing is reported.
The end effect is that no jobs are triggered in Jenkins.
Summary (13/12/2017)
The sshd daemon (Mina) would lost connection on one way connections and hitting some kind of timeout. That affected Zuul which idles with a gerrit stream-events.
Gerrit sshd.idleTimeout got set to 10 days as a workaround https://gerrit.wikimedia.org/r/#/c/58126/
Gerrit patch:
https://gerrit-review.googlesource.com/c/gerrit/+/44472 (79b91bfe) is the Gerrit patch.