Fix automatic backport workflow race condition

[amoghrajesh]

The automatic backport workflow was intermittently skipping PRs that should be backported, even when they had backport-to-* labels. After some investigation, I could see a race condition with GitHub's API.

Examples:

For successful runs:

Run actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea
  with:
    script: const { data: pullRequest } = await github.rest.repos.listPullRequestsAssociatedWithCommit({
      owner: context.repo.owner,
      repo: context.repo.repo,
      commit_sha: process.env.GITHUB_SHA
  });
  if (pullRequest.length > 0) {
      const pr = pullRequest[0];
      const backportBranches = pr.labels
            .filter(label => label.name.startsWith('backport-to-'))
            .map(label => label.name.replace('backport-to-', ''));
  
      console.log(`Commit ${process.env.GITHUB_SHA} is associated with PR ${pr.number}`);
      console.log(`Backport branches: ${backportBranches}`);
      core.setOutput('branches', JSON.stringify(backportBranches));
  } else {
      console.log('No pull request found for this commit.');
      core.setOutput('branches', '[]');
  }
  
    github-token: ***
    debug: false
    user-agent: actions/github-script
    result-encoding: json
    retries: 0
    retry-exempt-status-codes: 400,401,403,404,422
  env:
    COMMIT_SHA: c03fc7943009b02072ad275dd31e54f927bff889
    GITHUB_TOKEN: ***
Commit c03fc7943009b02072ad275dd31e54f927bff889 is associated with PR 57853
Backport branches: v3-1-test

For failed runs:

1s
Run actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea
  with:
    script: const { data: pullRequest } = await github.rest.repos.listPullRequestsAssociatedWithCommit({
      owner: context.repo.owner,
      repo: context.repo.repo,
      commit_sha: process.env.GITHUB_SHA
  });
  if (pullRequest.length > 0) {
      const pr = pullRequest[0];
      const backportBranches = pr.labels
            .filter(label => label.name.startsWith('backport-to-'))
            .map(label => label.name.replace('backport-to-', ''));
  
      console.log(`Commit ${process.env.GITHUB_SHA} is associated with PR ${pr.number}`);
      console.log(`Backport branches: ${backportBranches}`);
      core.setOutput('branches', JSON.stringify(backportBranches));
  } else {
      console.log('No pull request found for this commit.');
      core.setOutput('branches', '[]');
  }
  
    github-token: ***
    debug: false
    user-agent: actions/github-script
    result-encoding: json
    retries: 0
    retry-exempt-status-codes: 400,401,403,404,422
  env:
    COMMIT_SHA: caafc704462cc15bedde67ef416d870ceabd13e8
    GITHUB_TOKEN: ***
No pull request found for this commit.

The root cause seems to be that when a PR is merged to main, the workflow immediately queries GH listPullRequestsAssociatedWithCommit API to find the PR and check for backport labels. However, this API call seems to need time to process the merge and associate the commit with the PR.

Performed analysis on couple of PRs and this is my finding:

PR #	Commit (short)	Merge Time	Workflow Start	API Call Time	Time to API Call	Result	Current Status
57853	c03fc79	2025-11-17 13:42:26	13:42:29 (+3s)	13:42:33	7 seconds	Found	PR associated
58575	caafc70	2025-11-22 10:23:24	10:23:26 (+2s)	10:23:30	6 seconds	Not found	Now associated
58587	19e0a9a	2025-11-26 00:35:10	00:35:13 (+3s)	00:35:18	8 seconds	Not found	Now associated
58696	6d36d7b	2025-11-26 00:47:54	00:47:57 (+3s)	00:48:01	7 seconds	Not found	Now associated

To solve this, I have two options:

1. Add some sort of retry mechanism while calling the API. Complex implementation but could work.

2. [Chosen Now] Added a 15 second delay before querying the API. This gives the backend sufficient time to process the merge commit and establish the PR association, ensuring backport labels are consistently detected.

Why 15 seconds?

• Observed failures occurred at 6-8 seconds for my dataset
• 15 seconds provides ~2 times safety margin
• Simple solution that handles worst case timing

---

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[jscheffl]

Sleep is not cool but also no better idea. Thanks for the investigation! Wow this is complex :-D

[amoghrajesh]

@jscheffl I think I can also get it done by using retries in the API calls. But that will probably be more complex and time consuming to do

[github-actions]

Backport successfully created: v3-1-test

Status	Branch	Result
✅	v3-1-test