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kanta13jp1
kanta13jp1

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GitHub Actions Concurrency Patterns — cancel-in-progress: false for Parallel Deployments

#githubactions #cicd #flutter #buildinpublic

GitHub Actions Concurrency Patterns

The Problem: 5 Instances, All Pushing to Main

Running 5 parallel Claude Code instances means bursts of commits to main. Without concurrency configuration, deploy workflows pile up:

  • 5 simultaneous deploys competing for resources
  • Possible race condition where an older build overwrites a newer one
  • Timeouts from resource contention

cancel-in-progress: false is the Right Call for Deploys 

# .github/workflows/deploy-prod.yml
concurrency:
  group: deploy-prod
  cancel-in-progress: false  # queue mode — all runs execute in order
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The key distinction:

Use case cancel-in-progress
CI (PR builds) true — old PR builds are throwaway
Production deploy false — every commit should ship
Blog publishing false — don't skip any post
Scheduled tasks false — never skip a scheduled run

Concurrency Group Design 

# ❌ Single group for everything — all workflows block each other
concurrency:
  group: ci

# ✅ Separate by workflow
concurrency:
  group: ${{ github.workflow }}
  cancel-in-progress: false

# ✅ Per-PR CI — cancel old builds for the same PR
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true
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Full Deploy Config for Parallel Pushes 

name: Deploy to Production
concurrency:
  group: deploy-prod
  cancel-in-progress: false

on:
  push:
    branches: [main]
    paths:
      - 'lib/**'
      - 'web/**'
      - 'pubspec.yaml'
    paths-ignore:
      - 'docs/**'
      - '**.md'

jobs:
  deploy:
    runs-on: ubuntu-latest
    timeout-minutes: 30
    steps:
      - uses: actions/checkout@v4
      - run: firebase deploy --only hosting
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Always Set timeout-minutes

Without it, a hung job runs for 6 hours and blocks the concurrency queue:

jobs:
  build:
    timeout-minutes: 20   # Flutter Web build: ~10-15 min
  deploy:
    timeout-minutes: 10   # Firebase deploy: ~3-5 min
  lint:
    timeout-minutes: 5    # flutter analyze: ~2 min
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Filter Triggers With paths-ignore 

on:
  push:
    paths-ignore:
      - 'docs/**'
      - '**.md'
      - '.claude/**'
      - 'memory/**'
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Doc-only commits don't need a full deploy. With 5 active instances writing docs frequently, this saves significant CI minutes.

Summary 

deploys:         cancel-in-progress: false (queue, no skips)
PR checks:       cancel-in-progress: true  (latest wins)
scheduled tasks: cancel-in-progress: false (no skips)

timeout-minutes: always set on every job
paths-ignore:    exclude docs/*.md to reduce unnecessary triggers
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Concurrency config is a force multiplier for parallel dev workflows — get it wrong and your CI bills balloon; get it right and 5 instances push in harmony.

Building in public: https://my-web-app-b67f4.web.app/

GitHubActions #CI #Flutter #buildinpublic #DevOps

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