GitHub Merge Queue

Update - disabled Feb 14 2025

• branch protection (rulesets) set back to previous ie

  • combined main + release*

  • disallow force pushes to any branches

Issues found

• still runs all the checks (GHA) on merge group (PR enters merge queue) even if the PR is up to date - so we double up on CI - I think even if the queue is empty, definitely if a PR is removed from the queue

  • https://github.com/orgs/community/discussions/43988 - the issue has been closed and is apparently “exploratory” → https://github.com/github/roadmap/issues/824#issuecomment-2501843484

• GHA status not reported even though all workflows are complete and appear successful

  • maybe this? https://github.com/orgs/community/discussions/64027

• had to alter branch protection rules - merge queue creates temporary branches with a special prefix to validate pull request changes and we had a catchall branch protection disallowing force pushes to any branches. more info

• had to add “on merge” event for GHA workflows to be able to run required checks - more info

Update - Tried merge queue again since it’s out of beta and there’s a lot of approved PRs to merge

Action plan to try the experiment:

• enable merge queue on besu

  • you can't enable it on rulesets with * match so would need to duplicate the ruleset - have a separate one for release*

• merge this PR #8284 which hopefully will help with flaky ATs

• add a bunch of other PRs to merge queue - we live with the merge commit message being the PR description - there's 10 approved

  • would exclude the maintainer update - still voting

  • also the BadBlockManager - has an open q

  •  the gas limit one ? still has some open q's

  • so there's 7 to merge

• if it doesn't work (only problem I see being flaky tests mean merge queue doesn't help), can switch off merge queue again - back to status quo

Update - disabled ~ Mar 17 2023

Issues found

• still runs all the checks (including GHA) again even if the queue is empty https://github.com/orgs/community/discussions/46757?sort=top#discussioncomment-4912738

• GH enforcing the max 20 runners at once limit, which they never did before 

• hence PRs were being silently removed from the queue (GHA not reporting status) and no benefit was being gained from the queue

Update - enabled on Mar 13 2023. DCO required adjusting as per https://github.com/hyperledger/besu/pull/5207. 

Essentially this works the same as enabling auto-merge, except that any additional "merge from main" actions are automated.

Impacts on current workflow

• once the merge queue is enabled, it's a requirement - so all PRs will be merged via the queue.

• to add your PR to the merge queue, you need to click the green "merge when ready" button" just as you would click the "enable auto-merge" button

• "squash merge commits" is done automatically

  • with the commit message = PR title (full commit details still available in the PR)

  • so if you want to edit the commit message, you'll need to do this locally on your branch prior to adding it to the merge queue - eg https://stackoverflow.com/questions/25356810/git-how-to-squash-all-commits-on-branch

• avoiding unnecessary merge conflicts - think about inserting into a sensible place in the changelog, rather than appending to the end by default

• when there's a merge conflict, the PR with the conflicts gets kicked out of the merge queue and manual intervention is required - same as if you had enabled "auto-merge"

Discussion in Feb 28 contributor call on enabling the merge queue 2023-02-28 Contributor Call - APAC Friendly Time after 23.1.1 release

Note - it's part of "branch protection" - so you turn it on for specific branch protection rules.

This feature is still in beta - discussion https://github.blog/changelog/2023-02-08-pull-request-merge-queue-public-beta/

Link to Besu merge queue (when enabled) would be https://github.com/hyperledger/besu/queue/main