JMR-devandClaude Opus 4.8
05d06eb45b
End the merge cascade and give the traffic-controller ownership of CI *triggering*. - autoupdate.yml updates PR branches with the built-in GITHUB_TOKEN instead of a PAT, so an update push no longer auto-retriggers CI (GitHub's anti-recursion rule) — the cascade (every merge re-runs every PR, cancel-in-progress thrashing them) is gone. - New scheduler ci-trigger.yml -> traffic_control.py --mode trigger (re-)triggers CI for the highest-priority PR(s) whose head SHA has absent/stale checks, a few at a time (inflight cap), in the existing P0-P9 / broken-draft priority order — a poor-man's merge queue reusing the priority core. It runs after autoupdate finishes (workflow_run, race-free) plus a cron backstop plus manual dispatch. - Triggering uses workflow_dispatch, which is EXEMPT from anti-recursion, so the built-in GITHUB_TOKEN (actions: write) starts the run — NO PAT / secret change needed. - ci.yml gains a workflow_dispatch trigger (pr/head_sha/reason inputs) and a per-PR concurrency group unifying pull_request and dispatch runs; its on: pull_request path is kept so brand-new PRs, human pushes, and fork PRs always get CI (fail-open). Pure select_triggers / classify_sha_runs decision core added to traffic_control.py with 24 new unit tests (priority order, oldest-first fairness, inflight cap, fork skip, P0 bypass+preempt, head-SHA needy classification, and a liveness/anti-starvation simulation). Closes #349 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
86 lines
4.5 KiB
YAML
86 lines
4.5 KiB
YAML
# SPDX-License-Identifier: GPL-3.0-or-later
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name: CI trigger (traffic-controller)
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# The traffic-controller SCHEDULER (issue #349). It OWNS CI *triggering*. After main advances,
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# autoupdate.yml updates every behind PR's branch with the built-in GITHUB_TOKEN which, by
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# GitHub's anti-recursion rule, does NOT start CI — so those PRs sit with absent/stale required
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# checks on their new head SHA and cannot merge. This workflow then (re-)triggers CI for the
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# highest-priority such PR(s), a few at a time (an inflight cap), in the existing P0–P9 /
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# broken-draft priority order — a poor-man's merge queue that replaces the old "every merge
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# re-runs every PR" thundering herd (the cascade; see the ci-merge-cascade note + issue #349).
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#
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# HOW IT TRIGGERS: `traffic_control.py --mode trigger` runs `gh workflow run ci.yml --ref
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# <pr-head-branch>`. A workflow_dispatch is EXEMPT from the anti-recursion rule, so even the
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# built-in GITHUB_TOKEN's dispatch DOES start the run — no PAT is required (this job grants its
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# token `actions: write`). The dispatched run executes on the PR's head branch, so its checks
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# land on the PR head SHA and satisfy branch protection's required checks.
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#
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# WHEN IT RUNS:
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# • workflow_run, after "Auto-update PR branches" completes — the race-free moment: autoupdate
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# has finished moving branches to their new (checkless) head SHAs, so this pass sees exactly
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# the PRs that now need a run. (A bare `push: main` trigger would race autoupdate and often
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# read the pre-update SHAs, missing them until the next pass.)
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# • schedule (cron) — a backstop so no PR is ever permanently un-triggered even if a
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# workflow_run is missed/skipped (part of the fail-open guarantee), and so a brand-new PR
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# whose first `on: pull_request` run got cancelled is still picked up.
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# • workflow_dispatch — manual kick.
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#
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# FAIL-OPEN: the script guards every gh call and always exits 0; and structurally, ci.yml keeps
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# its `on: pull_request` trigger, so a human push (and a brand-new PR) always triggers CI
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# regardless of this scheduler — CI can never become permanently un-triggerable. Fork PRs (no
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# token/secret access) are skipped here and left to `on: pull_request`, so they are never wedged.
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on:
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workflow_run:
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workflows: ["Auto-update PR branches"]
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types: [completed]
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schedule:
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# Backstop cadence (UTC). GitHub may delay scheduled runs under load; that is fine — this
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# is only a safety net behind the immediate workflow_run trigger above.
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- cron: "*/15 * * * *"
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workflow_dispatch:
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# Trigger-only; this workflow never gates a merge. `actions: write` lets the built-in
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# GITHUB_TOKEN dispatch ci.yml (workflow_dispatch) and cancel strictly-lower runs when a P0
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# emergency preempts. `pull-requests: read` + `contents: read` cover the PR/label enumeration.
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permissions:
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contents: read
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pull-requests: read
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actions: write
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# One trigger pass at a time. Do NOT cancel an in-flight pass (cancel-in-progress: false):
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# a half-finished pass could leave some needy PRs un-triggered until the next pass.
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concurrency:
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group: ci-trigger
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cancel-in-progress: false
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jobs:
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trigger:
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name: Trigger CI by priority
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runs-on: ubuntu-latest
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timeout-minutes: 10 # generous backstop; the script only enumerates + dispatches, no waits
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steps:
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- name: Check out source
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uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
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- name: Set up Python
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uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
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with:
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python-version: "3.x"
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# gh is auto-configured from GH_TOKEN / GH_REPO. The script guards every gh call and
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# always exits 0, so a hiccup (API error, missing permission, fork PR) can never wedge CI
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# — and even a total failure here leaves ci.yml's `on: pull_request` path intact.
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- name: Trigger CI for the highest-priority PR(s) needing a run
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env:
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GH_TOKEN: ${{ github.token }}
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GH_REPO: ${{ github.repository }}
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# Poor-man's merge-queue width: at most this many PRs run CI concurrently under the
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# scheduler (a P0 emergency bypasses this cap). Kept conservative because each PR
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# fans out to the whole E2E matrix (~8 API levels + preview); this is the main knob
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# to raise for throughput vs runner budget. The coordinator drives runner allocation.
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MAX_INFLIGHT_RUNS: "2"
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# The workflow file the scheduler enumerates runs for and dispatches.
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CI_WORKFLOW_FILE: "ci.yml"
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run: python3 .github/scripts/traffic_control.py --mode trigger
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