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Github Action

Github Actions(CI/CD) tricks that official documents didn't mention. This post including hints, tips, snippet, cheatsheet, troubleshooting, notes, how-to.

Github Actions: an overview

In Actions, the build occurs as follows (see Introduction to GitHub Actions ):

  • event (for example, a pull request or a commit to the repository, see the list here >>> ) triggers the start of the workflow , and the workflow contains jobs
  • job contains a list of steps , and each step contains one or more actions
  • actions are executed on the same runner , and several such actions can be executed within the same workflow at the same time

Main components:

  • runner : the Github or self-hosted server that runs the job
  • workflow : a described procedure that includes one or more jobs that is triggered by some event
  • jobs : a set of steps that run on the same runner. If there are several jobs in one workflow, by default they are launched in parallel, but they can be configured to be executed in turn and depend on the results of each other's execution.
  • steps : a task that executes commands or actions. Since steps in one job are performed on one runner, they can exchange data with each other.
  • actions : main "executable blocks" - can represent a set of ready-made tasks, or execute ordinary commands

Adding a workflow file

mkdir -p .github / workflows

name: actions-test
on: [push]
jobs:
  print-hello:
    runs-on: ubuntu-latest
    steps:
      - run: echo "Hello, world"

Events

In Events, you can describe rather complex conditions, according to which you will make a decision on the execution of a workflow.

name: actions-test
on: 
  push:
    branches:
      - master
  pull_request:
    branches:
      - test-branch

Scheduled events

name: actions-test
on: 
  schedule:
    - cron: '* * * *'

Manual start - workflow_dispatch

name: actions-test
on: 
   workflow_dispatch
jobs:
  print-hello:
    runs-on: ubuntu-latest
    steps:
      - run: echo "Hello, world"
After that, a button will appear in Actions to start with a choice of a branch:

workflow_dispatch

In addition, a set of input data can be added here, using inputswhich at runtime will be saved in the context github.eventand available as variables: 

name: actions-test
on: 
   workflow_dispatch:
     inputs:
       userName:
         description: "Username"
         required: true
         default: "test"
jobs:
  print-hello:
    runs-on: ubuntu-latest
    steps:
      - run: echo "Username: $ {{github.event.inputs.username}}"
      - run: echo "Actor's username: $ {{github.actor}}"

Webhooks: create

In addition pushto the one we have already used, you can configure the start of the workflow for any event in the repository.

name: actions-test
on: 
  create
jobs:
  print-hello:
    runs-on: ubuntu-latest
    steps:
      - run: |
          echo "Event name: $ {{github.event_name}}"
          echo "Actor's username: $ {{github.actor}}"

Environment variables

Also, Github Actions supports working with environment variables.

name: vars-test

on:
  push

env:
  VAR_NAME: "Global value"

jobs:
  print-vars:
    runs-on: ubuntu-latest
    steps:

      # using own varibales
      - name: "Test global var as $VAR_NAME"
        run: echo "Test value $VAR_NAME"

      - name: "Test global var as ${{ env.VAR_NAME }}"
        run: echo "Test value ${{ env.VAR_NAME }}"

      # using default variables
      - name: "Test job var as $GITHUB_REPOSITORY"
        run: echo "Test value $GITHUB_REPOSITORY"

      # this will be empty, as default variables are not in the context
      - name: "Test job var as ${{ env.GITHUB_REPOSITORY }}"
        run: echo "Test value ${{ env.GITHUB_REPOSITORY }}"

      # using 'dynamic' variables
      - name: "Set local var"
        run: echo "local_var=local value" >> $GITHUB_ENV

      - name: "Print local var as $local_var"
        run: echo "$local_var"

      - name: "Print local var as ${{ env.local_var }}"
        run: echo "${{ env.local_var }}"
And the result:

environment

Secrets

Secrets are added in repository settings> Secrets:

secret

name: actions-test

on: 
  push

env:
  TEST_ENV: ${{ secrets.TEST_SECRET }}

jobs:
  print-hello:
    runs-on: ubuntu-latest
    steps:
      - run: |
          echo "Test secret: ${{ secrets.TEST_SECRET }}"
          echo "Test secret: ${{ env.TEST_ENV }}"

Run:

run-secret

Last update: August 17, 2021

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