How to Use a Static Concurrency Group for a Singleton Job in GitHub Actions

A constant group name (no context expressions) forces every run of a job into a single global lane.

For a job that touches a shared external resource (a migration runner, a terraform state), use a fixed group string. Every run repo-wide shares it, so at most one runs while the rest queue.

Steps

• Set concurrency.group to a literal string with no expressions.
• Set cancel-in-progress: false so the running instance always finishes.
• Scope it to the job if only that job must be a singleton.

Workflow

jobs:
  migrate:
    runs-on: ubuntu-latest
    concurrency:
      group: db-migrations
      cancel-in-progress: false
    steps:
      - uses: actions/checkout@v4
      - run: ./run-migrations.sh

Gotchas

• A static group is a repo-wide lock, so a hung run blocks every other invocation until it ends.
• Only one pending run is retained per group; extra queued runs are canceled while pending.

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