Dependent Jobs

Teaching 5 min

Exercises 5 min

Estimated 10 min

Questions

How do you make some jobs run after other jobs?

Objectives

Run some jobs in serial.

Defining dependencies

From the last session, we’re starting with

jobs:
  greeting:
    runs-on: ubuntu-latest
    steps:
      - run: echo hello world

  build_skim:
    runs-on: ubuntu-latest
    container: rootproject/root:${{ matrix.version }}
    strategy:
      matrix:
        version: [6.26.10-conda, latest]
    steps:
      - name: checkout repository
        uses: actions/checkout@v4

      - name: build
        run: |
          COMPILER=$(root-config --cxx)
          FLAGS=$(root-config --cflags --libs)
          $COMPILER -g -O3 -Wall -Wextra -Wpedantic -o skim skim.cxx $FLAGS

jobs:
  greeting:
    runs-on: ubuntu-latest
    steps:
      - run: echo hello world

  build_skim:
    runs-on: ubuntu-latest
    container: rootproject/root:${{ matrix.version }}
    strategy:
      matrix:
        version: [6.26.10-conda, latest]
    steps:
      - name: install node
        run: wget -qO- https://nodejs.org/dist/v20.18.1/node-v20.18.1-linux-x64.tar.gz | tar -xz -C /usr/local --strip-components=1

      - name: checkout repository
        uses: actions/checkout@v4

      - name: build
        run: |
          COMPILER=$(root-config --cxx)
          FLAGS=$(root-config --cflags --libs)
          $COMPILER -g -O3 -Wall -Wextra -Wpedantic -o skim skim.cxx $FLAGS

We’re going to talk about another useful parameter needs.

Specify dependencies between jobs

The key-value needs: job or list of jobs allows you to specify dependencies between jobs in the order you define.
Example:

job2:
  needs: job1

job2 waits until job1 completes successfully. Further reading.

Challenge

Dependent jobs

How to make build_skim job run after greeting?

Solution

jobs:
  greeting:
    runs-on: ubuntu-latest
    steps:
      - run: echo hello world

  build_skim:
    needs: greeting
    runs-on: ubuntu-latest
    container: rootproject/root:${{ matrix.version }}
    strategy:
      matrix:
        version: [6.26.10-conda, latest]
    steps:
      - name: checkout repository
        uses: actions/checkout@v4

      - name: build
        run: |
          COMPILER=$(root-config --cxx)
          FLAGS=$(root-config --cflags --libs)
          $COMPILER -g -O3 -Wall -Wextra -Wpedantic -o skim skim.cxx $FLAGS

jobs:
  greeting:
    runs-on: ubuntu-latest
    steps:
      - run: echo hello world

  build_skim:
    needs: greeting
    runs-on: ubuntu-latest
    container: rootproject/root:${{ matrix.version }}
    strategy:
      matrix:
        version: [6.26.10-conda, latest]
    steps:
      - name: install node
        run: wget -qO- https://nodejs.org/dist/v20.18.1/node-v20.18.1-linux-x64.tar.gz | tar -xz -C /usr/local --strip-components=1

      - name: checkout repository
        uses: actions/checkout@v4

      - name: build
        run: |
          COMPILER=$(root-config --cxx)
          FLAGS=$(root-config --cflags --libs)
          $COMPILER -g -O3 -Wall -Wextra -Wpedantic -o skim skim.cxx $FLAGS

Let’s go ahead and add those changes and look at GitHub.

git add .github/workflows/main.yml
git commit -m "add dependent jobs"
git push -u origin feature/add-actions

Key Points

We can specify dependencies between jobs running in a series using the needs value.

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