Sheriffing/How To/Backouts: Difference between revisions
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When a patch is landed that causes build or test failures, it must be backed out to restore the tree to a passing state again. This page documents the procedure for performing backouts both for Gecko changes and Gaia. | When a patch is landed that causes build or test failures, it must be backed out to restore the tree to a passing state again. This page documents the procedure for performing backouts both for Gecko changes and Gaia. | ||
= New recommended way of backouts = | |||
* With unified repos backouts are now more easily - please follow [[Sheriffing/How:To:SheriffingFromUnifiedRepos|Unified Repos Backup]] | |||
= Gecko Backouts = | = Gecko Backouts = | ||
| Line 33: | Line 38: | ||
* If the commit message needs to be modifying after qfinish (i.e. forgotten CLOSED TREE), hg commit --amend will open the backout in an editor for modification. | * If the commit message needs to be modifying after qfinish (i.e. forgotten CLOSED TREE), hg commit --amend will open the backout in an editor for modification. | ||
= Best Practices and Communication = | = Best Practices and Communication = | ||
Revision as of 12:04, 14 June 2017
When a patch is landed that causes build or test failures, it must be backed out to restore the tree to a passing state again. This page documents the procedure for performing backouts both for Gecko changes and Gaia.
New recommended way of backouts
- With unified repos backouts are now more easily - please follow Unified Repos Backup
Gecko Backouts
Prerequisites
- Install the qbackout extension from https://hg.mozilla.org/hgcustom/version-control-tools/file/default/hgext/qbackout
- Instructions: https://hg.mozilla.org/hgcustom/version-control-tools/file/default/hgext/qbackout/README
Usage
Backout of a single changeset
hg qbackout -e -r 123456789abc
Where -r is the specific revision to be backed out. The -e option opens an editor to edit the commit message prior to committing. This is useful for adding DONTBUILD, CLOSED TREE, etc before pushing.
Backout of multiple consecutive changesets
hg qbackout -e -s -r 123456789abc:cba987654321
Where the -r is now specifying a range of commits (from 123456789abc to cba987654321). The -s option commits the backouts as a single commit. Otherwise, each changeset in the range will be backed out as separate commits.
Backout of multiple non-consecutive changesets
hg qbackout -e -s -r 123456789abc+cba987654321
Useful when there are commits in between the ones that need backing out.
Backout of a combination of consecutive and non-consecutive changesets
hg qbackout -e -s -r 123456789abc:cba987654321+xyz456789123
Useful when a follow-up patch needs backing out in addition to the main one (i.e. someone had a follow-up bustage fix push) or an additional commit conflicts with the backout and needs backing out as well.
Pushing
hg qfinish -a hg push
Finalizes the patch for pushing to the remote repo.
What Ifs
- If the remote repo has additional changesets (i.e. a push race), hg pull --rebase will pull the new changesets and rebase the local changes on top of them.
- This requires the rebase extension to be enabled in .hgrc
- If the commit message needs to be modifying after qfinish (i.e. forgotten CLOSED TREE), hg commit --amend will open the backout in an editor for modification.
Best Practices and Communication
Based on Feedback from the Sheriff Survey, when you have to do a backout some best practice
- Ping the Developer in IRC if possible and when the developer is around, this gives the developer a chance to fix the problem and so avoid a backout. Some of the sheriffs use a 5 minute rule for the waiting of a response of the developer
- Set Need-info! This is very important! Developers get a lot of bugmail and so a backout comment can be missed - please make sure that you set a need-info to the developer in the bug when doing a backout
- Make sure that the failures that lead to the backout are stared in treeherder - this helps a lot also the following sheriffs.