# Configuring CI Using GitHub Actions and Nx

Below is an example of a GitHub setup for an Nx workspace - building and testing only what is affected. For more details on how the action is used, head over to the [official docs](https://github.com/marketplace/actions/nx-set-shas).

```yaml {% fileName=".github/workflows/ci.yml" %}
name: CI
on:
  push:
    branches:
      - main
  pull_request:

jobs:
  main:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - uses: actions/setup-node@v3
        with:
          node-version: 20
          cache: 'npm'
      - run: npm ci
      - uses: nrwl/nx-set-shas@v3
      - run: git branch --track main origin/main

      - run: npx nx format:check
      - run: npx nx affected -t lint,test,build --parallel=3
```

`GitHub` can track the last successful run on the `main` branch and use this as a reference point for the `BASE`. The `Nx Set SHAs` provides a convenient implementation of this functionality which you can drop into your existing CI config.
To understand why knowing the last successful build is important for the affected command, check out the [in-depth explanation in Actions's docs](https://github.com/marketplace/actions/nx-set-shas#background).

## Distributed Task Execution with Nx Cloud

Read more about [Distributed Task Execution (DTE)](/core-features/distribute-task-execution). Use this [reusable GitHub workflow](https://github.com/nrwl/ci) to quickly set up DTE for your organization.

```yaml {% fileName=".github/workflows/ci.yml" %}
name: CI
on:
  push:
    branches:
      - main
  pull_request:

jobs:
  main:
    name: Nx Cloud - Main Job
    uses: nrwl/ci/.github/workflows/nx-cloud-main.yml@v0.13.0
    with:
      number-of-agents: 3
      parallel-commands: |
        npx nx-cloud record -- npx nx format:check
      parallel-commands-on-agents: |
        npx nx affected -t lint,test,build --parallel=3

  agents:
    name: Nx Cloud - Agents
    uses: nrwl/ci/.github/workflows/nx-cloud-agents.yml@v0.13.0
    with:
      number-of-agents: 3
```

You can also use our [ci-workflow generator](/nx-api/workspace/generators/ci-workflow) to generate the workflow file.

## Custom distributed CI with Nx Cloud

Our [reusable GitHub workflow](https://github.com/nrwl/ci) represents a good set of defaults that works for a large number of our users. However, reusable GitHub workflows come with their [limitations](https://docs.github.com/en/actions/using-workflows/reusing-workflows).

If the reusable workflow above doesn't satisfy your needs you should create a custom workflow. This is what the GitHub workflow above roughly encapsulates:

```yaml {% fileName=".github/workflows/ci.yml" %}
name: CI
on:
  push:
    branches:
      - main
  pull_request:

env:
  NX_CLOUD_DISTRIBUTED_EXECUTION: true # this enables DTE
  NX_CLOUD_DISTRIBUTED_EXECUTION_AGENT_COUNT: 3 # expected number of agents
  NX_BRANCH: ${{ github.event.number || github.ref_name }}
  NX_CLOUD_ACCESS_TOKEN: ${{ secrets.NX_CLOUD_ACCESS_TOKEN }}
  NPM_TOKEN: ${{ secrets.NPM_TOKEN }} # this is needed if our pipeline publishes to npm

jobs:
  main:
    name: Nx Cloud - Main Job
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        name: Checkout [Pull Request]
        if: ${{ github.event_name == 'pull_request' }}
        with:
          # By default, PRs will be checked-out based on the Merge Commit, but we want the actual branch HEAD.
          ref: ${{ github.event.pull_request.head.sha }}
          # We need to fetch all branches and commits so that Nx affected has a base to compare against.
          fetch-depth: 0

      - uses: actions/checkout@v4
        name: Checkout [Default Branch]
        if: ${{ github.event_name != 'pull_request' }}
        with:
          # We need to fetch all branches and commits so that Nx affected has a base to compare against.
          fetch-depth: 0

      # Set node/npm/yarn versions using volta
      - uses: volta-cli/action@v4
        with:
          package-json-path: '${{ github.workspace }}/package.json'

      - name: Use the package manager cache if available
        uses: actions/setup-node@v3
        with:
          node-version: 20
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Check out the default branch
        run: git branch --track main origin/main

      - name: Initialize the Nx Cloud distributed CI run
        run: npx nx-cloud start-ci-run

      - name: Run commands in parallel
        run: |
          pids=()
          # list of commands to be run on main has env flag NX_CLOUD_DISTRIBUTED_EXECUTION set to false
          NX_CLOUD_DISTRIBUTED_EXECUTION=false npx nx-cloud record -- npx nx format:check & pids+=($!)

          # list of commands to be run on agents
          npx nx affected -t lint,test,build --parallel=3 & 
          pids+=($!)

          # run all commands in parallel and bail if one of them fails
          for pid in ${pids[*]}; do
            if ! wait $pid; then
              exit 1
            fi
          done

          exit 0

      - name: Stop all running agents for this CI run
        # It's important that we always run this step, otherwise in the case of any failures in preceding non-Nx steps, the agents will keep running and waste billable minutes
        if: ${{ always() }}
        run: npx nx-cloud stop-all-agents

  agents:
    name: Agent ${{ matrix.agent }}
    runs-on: ubuntu-latest
    strategy:
      matrix:
        agent: [1, 2, 3]
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      # Set node/npm/yarn versions using volta
      - uses: volta-cli/action@v4
        with:
          package-json-path: '${{ github.workspace }}/package.json'

      - name: Use the package manager cache if available
        uses: actions/setup-node@v3
        with:
          node-version: 20
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Start Nx Agent ${{ matrix.agent }}
        run: npx nx-cloud start-agent
        env:
          NX_AGENT_NAME: ${{ matrix.agent }}
```