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Topic on Talk:Continuous integration/Zuul

Problems caused by force merge

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Adamw (talkcontribs)

I remember that there have been some deadlocks caused every time devs did a force merge, and allegedly there is still a type of slowness which happens after a force merge, but I'm not clear on the details. It would be great to discuss here (if this is the right place), or link to a Phabricator task which discusses the issue.

Hashar (talkcontribs)
Adamw (talkcontribs)

Thanks, the explanation in that task helps me understand what causes the issue. I think I also understand that it's a bit of a race condition and depends on repo configuration, which is why it sometimes crashes Jenkins/Gearman and sometimes does not.

What do you think about these potential improvements to the situation?

  • When Zuul tries to merge a change but the change is already (force) merged:
    • If the resulting merged file tree is identical to what was already merged, then the merge step will complete successfully, as if we had performed the merge. Post-merge steps will still run.
    • If the resulting merge is different than what was already merged, Jenkins posts a V-1 to the change and reports, "Unexpected merge detected /o\"
  • When Zuul reports V-1 on a change but the change is already (force) merged:
    • Maybe Jenkins then posts a V-2, or just another V-1, with the message "Unexpected merge of failing change, please take action to correct!"
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