Screenshot of Zuul status

A few hours ago the Zuul queue started to get stuck. A stack of three changes in mediawiki-extensions-DonationInterface was reviewed with CodeReview+3. The top one (commit C, depending on B, depending on A) had a merge conflict in it.

C https://gerrit.wikimedia.org/r/#/c/166678/3
B https://gerrit.wikimedia.org/r/#/c/166803/1
A https://gerrit.wikimedia.org/r/#/c/166889/2

Somehow this caused Zuul's gate-and-submit pipeline to get stuck indefinitely. Even changes from mwext-VisualEditor, mediawiki-core, mwext-MobileFrontend were all waiting.

Debug information from Zuul's log

-------

```
$ cat /var/log/zuul/zuul.log.2014-10-15 | grep '166678,3'
2014-10-15 19:17:14,453 INFO zuul.Gerrit: Updating information for 166678,3
2014-10-15 19:17:15,169 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0ff0590 166678,3> to <Pipeline check-only>
2014-10-15 19:17:15,169 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0ff0590 166678,3> to <Pipeline check-voter>
2014-10-15 19:17:15,170 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0ff0590 166678,3> to <Pipeline test>
2014-10-15 19:17:15,171 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b0ff0590 166678,3> depends on changes []
2014-10-15 19:17:17,470 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b0ff0590 166678,3> depends on changes []
2014-10-15 19:17:17,470 INFO zuul.Gearman: Launch job mwext-DonationInterface-lint for change <Change 0x7f17b0ff0590 166678,3> with dependent changes []
2014-10-15 19:17:17,474 INFO zuul.Gearman: Launch job mwext-DonationInterface-npm for change <Change 0x7f17b0ff0590 166678,3> with dependent changes []
2014-10-15 19:17:19,481 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b0ff0590 166678,3> depends on changes []
2014-10-15 19:17:19,481 INFO zuul.Gearman: Launch job mwext-DonationInterface-testextension for change <Change 0x7f17b0ff0590 166678,3> with dependent changes []
2014-10-15 19:18:08,759 INFO zuul.IndependentPipelineManager: Reporting change <Change 0x7f17b0ff0590 166678,3>, actions: [<ActionReporter <zuul.reporter.gerrit.Reporter object at 0x1b6c310>, {'verified': 2}>]
2014-10-15 19:18:08,842 INFO zuul.Gerrit: Updating information for 166678,3
2014-10-15 23:21:16,969 INFO zuul.Gerrit: Updating information for 166678,3
2014-10-15 23:21:17,284 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0ff0590 166678,3> to <Pipeline gate-and-submit>
2014-10-15 23:21:17,284 INFO zuul.DependentPipelineManager: Reporting start, action [<ActionReporter <zuul.reporter.gerrit.Reporter object at 0x1b6c310>, {'verified': 0}>] change <Change 0x7f17b0ff0590 166678,3>
2014-10-15 23:21:17,359 INFO zuul.Gerrit: Updating information for 166678,3
2014-10-15 23:21:17,362 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0ff0590 166678,3> depends on changes [<Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:30,406 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,790 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,790 INFO zuul.Gearman: Launch job mediawiki-gate for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,794 INFO zuul.Gearman: Launch job mwext-DonationInterface-lint for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,798 INFO zuul.Gearman: Launch job mwext-DonationInterface-npm for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:48:30,564 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b13caed0 166889,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:50:13,976 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:50:13,976 INFO zuul.Gearman: Launch job mwext-DonationInterface-testextension for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:59:51,805 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0c3d250 166918,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,864 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0c3d250 166918,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,864 INFO zuul.Gearman: Launch job mwext-VisualEditor-qunit for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,868 INFO zuul.Gearman: Launch job mwext-VisualEditor-bundle-rubocop for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,876 INFO zuul.Gearman: Launch job mwext-VisualEditor-phpcs-HEAD for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,884 INFO zuul.Gearman: Launch job mediawiki-gate for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,888 INFO zuul.Gearman: Launch job mwext-VisualEditor-npm for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,893 INFO zuul.Gearman: Launch job mwext-VisualEditor-lint for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,957 INFO zuul.Gearman: Launch job mwext-VisualEditor-doc-test for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:56,023 INFO zuul.Gearman: Launch job experiment-gating-dependencies for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
[00:45 UTC] zuul at gallium.wikimedia.org in /srv/org/wikimedia/integration ((no branch)%)
```

-------

```
$ cat /var/log/zuul/zuul.log.2014-10-15 | grep '166803,1'
2014-10-15 19:38:32,047 INFO zuul.Gerrit: Updating information for 166803,1
2014-10-15 19:38:32,382 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0f64c10 166803,1> to <Pipeline check-only>
2014-10-15 19:38:32,405 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0f64c10 166803,1> to <Pipeline check-voter>
2014-10-15 19:38:32,406 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0f64c10 166803,1> to <Pipeline test>
2014-10-15 19:38:32,407 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes []
2014-10-15 19:38:34,115 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes []
2014-10-15 19:38:34,115 INFO zuul.Gearman: Launch job mwext-DonationInterface-lint for change <Change 0x7f17b0f64c10 166803,1> with dependent changes []
2014-10-15 19:38:34,119 INFO zuul.Gearman: Launch job mwext-DonationInterface-npm for change <Change 0x7f17b0f64c10 166803,1> with dependent changes []
2014-10-15 19:38:35,718 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes []
2014-10-15 19:38:35,718 INFO zuul.Gearman: Launch job mwext-DonationInterface-testextension for change <Change 0x7f17b0f64c10 166803,1> with dependent changes []
2014-10-15 19:38:48,199 INFO zuul.IndependentPipelineManager: Reporting change <Change 0x7f17b0f64c10 166803,1>, actions: [<ActionReporter <zuul.reporter.gerrit.Reporter object at 0x1b6c310>, {'verified': 2}>]
2014-10-15 19:38:48,273 INFO zuul.Gerrit: Updating information for 166803,1
2014-10-15 19:40:23,214 INFO zuul.Gerrit: Updating information for 166803,1
2014-10-15 19:40:23,668 INFO zuul.Gerrit: Updating information for 166803,1
2014-10-15 23:47:29,998 INFO zuul.Gerrit: Updating information for 166803,1
2014-10-15 23:47:30,326 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b0f64c10 166803,1> to <Pipeline gate-and-submit>
2014-10-15 23:47:30,327 INFO zuul.DependentPipelineManager: Reporting start, action [<ActionReporter <zuul.reporter.gerrit.Reporter object at 0x1b6c310>, {'verified': 0}>] change <Change 0x7f17b0f64c10 166803,1>
2014-10-15 23:47:30,402 INFO zuul.Gerrit: Updating information for 166803,1
2014-10-15 23:47:30,406 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,790 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,790 INFO zuul.Gearman: Launch job mediawiki-gate for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,794 INFO zuul.Gearman: Launch job mwext-DonationInterface-lint for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:47:31,798 INFO zuul.Gearman: Launch job mwext-DonationInterface-npm for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:48:30,564 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b13caed0 166889,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:50:13,976 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0f64c10 166803,1> depends on changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:50:13,976 INFO zuul.Gearman: Launch job mwext-DonationInterface-testextension for change <Change 0x7f17b0f64c10 166803,1> with dependent changes [<Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:59:51,805 INFO zuul.DependentPipelineManager: Resetting builds for change <Change 0x7f17b0c3d250 166918,2> because the item ahead, <QueueItem 0x7f180b290c10 for <Change 0x7f17b13caed0 166889,2> in gate-and-submit>, is not the nearest non-failing item, <QueueItem 0x7f17b10042d0 for <Change 0x7f17b0f64c10 166803,1> in gate-and-submit>
2014-10-15 23:59:51,805 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0c3d250 166918,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,864 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b0c3d250 166918,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,864 INFO zuul.Gearman: Launch job mwext-VisualEditor-qunit for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,868 INFO zuul.Gearman: Launch job mwext-VisualEditor-bundle-rubocop for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,876 INFO zuul.Gearman: Launch job mwext-VisualEditor-phpcs-HEAD for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,884 INFO zuul.Gearman: Launch job mediawiki-gate for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,888 INFO zuul.Gearman: Launch job mwext-VisualEditor-npm for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,893 INFO zuul.Gearman: Launch job mwext-VisualEditor-lint for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:55,957 INFO zuul.Gearman: Launch job mwext-VisualEditor-doc-test for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
2014-10-15 23:59:56,023 INFO zuul.Gearman: Launch job experiment-gating-dependencies for change <Change 0x7f17b0c3d250 166918,2> with dependent changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>]
```

-------

```
$ cat /var/log/zuul/zuul.log.2014-10-15 | grep '166889,2'
2014-10-15 22:33:35,953 INFO zuul.Gerrit: Updating information for 166889,2
2014-10-15 22:33:36,261 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b13caed0 166889,2> to <Pipeline check-only>
2014-10-15 22:33:36,261 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b13caed0 166889,2> to <Pipeline check-voter>
2014-10-15 22:33:36,262 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b13caed0 166889,2> to <Pipeline test>
2014-10-15 22:33:36,263 INFO zuul.IndependentPipelineManager: Change <Change 0x7f17b13caed0 166889,2> depends on changes []
2014-10-15 22:33:39,803 INFO zuul.IndependentPipelineManager: Unable to merge change <Change 0x7f17b13caed0 166889,2>
2014-10-15 22:33:39,803 INFO zuul.IndependentPipelineManager: Reporting change <Change 0x7f17b13caed0 166889,2>, actions: [<ActionReporter <zuul.reporter.gerrit.Reporter object at 0x1b6c310>, {'verified': -1}>]
2014-10-15 22:33:39,876 INFO zuul.Gerrit: Updating information for 166889,2
2014-10-15 23:48:30,171 INFO zuul.Gerrit: Updating information for 166889,2
2014-10-15 23:48:30,484 INFO zuul.Scheduler: Adding mediawiki/extensions/DonationInterface, <Change 0x7f17b13caed0 166889,2> to <Pipeline gate-and-submit>
2014-10-15 23:48:30,484 INFO zuul.DependentPipelineManager: Reporting start, action [<ActionReporter <zuul.reporter.gerrit.Reporter object at 0x1b6c310>, {'verified': 0}>] change <Change 0x7f17b13caed0 166889,2>
2014-10-15 23:48:30,559 INFO zuul.Gerrit: Updating information for 166889,2
2014-10-15 23:48:30,564 INFO zuul.DependentPipelineManager: Change <Change 0x7f17b13caed0 166889,2> depends on changes [<Change 0x7f17b0f64c10 166803,1>, <Change 0x7f17b0ff0590 166678,3>, <Change 0x7f17b0c2e750 166607,6>]
2014-10-15 23:48:31,761 INFO zuul.DependentPipelineManager: Unable to merge change <Change 0x7f17b13caed0 166889,2>
2014-10-15 23:59:51,805 INFO zuul.DependentPipelineManager: Resetting builds for change <Change 0x7f17b0c3d250 166918,2> because the item ahead, <QueueItem 0x7f180b290c10 for <Change 0x7f17b13caed0 166889,2> in gate-and-submit>, is not the nearest non-failing item, <QueueItem 0x7f17b10042d0 for <Change 0x7f17b0f64c10 166803,1> in gate-and-submit>
```

--------------------------
**Version**: wmf-deployment
**Severity**: normal
**See Also**:
https://launchpad.net/bugs/1358517

**Attached**: {F15298}