DevOps Classroom notes 05/Apr/2026

Github actions

Variables in Github Actions

Environmental Variables

• These are values we can define inside the workflow YAML, job or step.
• They are good for non-sensitive runtime values like
  • app-name
  • region
  • port
  • build mode
• Thy are available through shell syntax inside run steps and also env context in workflow expressions

Configuration variables

• These are non-sensitve variables store in Github itself at the organization, repository or environmental level.
• They are accessed using vars context `${{ vars.APP_NAME }}

Secrets

• These are for sensitive values like tokens, passwords API keys.
• Github stores them encrypted
• They are only available in workflows if you explicitly reference them
• They can exist at the organization level, repository or environment level

Levels

• Github supports storage at multiple level
  • Repository Level: A variable or secret belongs to one repository
  • Organization Level: A variable or secret that can be shared across multiple repos in organization
  • Environment: A variable or secret belongs to a specific environment such as dev, qa or prod

Context

• A context is structured data provided by github during workflow execution Refer Here
• It gives your workflow information about
  • repo
  • commit
  • user
  • job
  • environments
• Syntax ${{ context_name.property }}

Lets create a variable at multiple levels and use them in github actions

• Watch classroom recording for ui navigation
• Refer Here for the changes

Variables syntaxes in Github

• The three core syntaxes
• Expression Syntax ${{ ... }}
• SHELL syntax $VAR
• POWERSHELL syntax $env.VAR
• Rule
  • ${{ }} Github processes before execution
  • $VAR Runner processes during execution
• Before Execution:
  • Github Engine reads your yaml
  • Evaluates ${{ }}
  • Decides
    • which jobs run
    • which steps run
    • what values to inject
• During Execution:
  • At Runner machine
  • Executes the command
  • understands $VAR
  • Runs shell/pwsh scripts
• Scenairo where this matter
  • conditional execution
  • Injecting secrets
  • Matrix builds

Github Action functions and operators

• Refer Here for fucntions and Refer Here for operators

Example

• if the current branch is main contains the value as True
  • Print the github context
  • print the vars context
• Build some project Refer Here for the sample

Conditionals

• Conditional job execution Refer Here and Refer Here for syntax item
• Conditional step execution Refer Here for syntax
• Refer Here for conditions

Example

• I have a java project, i want to build using
  • java 17
  • java 21

Strategy in Github Actions

• Refer Here
• For using a specific version you should find a reusable action such as setup

Publishing artifacts

• Github gives two options
  • A link to downlad a repo (temporary)
  • A package repository
• For package repositories we have options such as
  • Artifactory (jfrog)
  • Nexus
  • Github Packages

Lets create a git-flow for spring-petclinic

• I will create workflows for i.e. we have two options a jar file and a docker image
  • Maven
  • Docker
• On Dev branches i want to give options to user to view the package built
• refer the below github action

---
name: dev-branch

on:
    push:
        branches:
          - dev

jobs:
    maven-build-job:
        runs-on: ubuntu-latest

        permissions:
            contents: read
            packages: write
            security-events: write

        steps:
          - name: get the code
            uses: actions/checkout@v6
          - name: setup java
            uses: actions/setup-java@v5
            with:
                java-version: '21'
                distribution: 'temurin'
          - name: cache maven dependencies
            uses: actions/cache@v4
            with:
                path: ~/.m2/repository
                key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
                restore-keys: ${{ runner.os }}-maven-
          - name: Initialize CodeQL
            uses: github/codeql-action/init@v4
            with:
                languages: java
          - name: package the code
            run: mvn clean package
          - name: Perform code quality analysis
            uses: github/codeql-action/analyze@v4
          - name: upload JAR as artifact
            uses: actions/upload-artifact@v4
            with:
                name: petclinic-jar
                path: target/*.jar

    docker-build-job:
        runs-on: ubuntu-latest
        steps:
            - name: get the code
              uses: actions/checkout@v6
            - name: Set up Docker Buildx
              uses: docker/setup-buildx-action@v4
            - name: build docker image
              uses: docker/build-push-action@v7
              with:
                push: false
                tags: "cicdprojects/springpetclinic:latest"

• In this specifically

- name: upload JAR as artifact
  uses: actions/upload-artifact@v4
  with:
    name: petclinic-jar
    path: target/*.jar

• From release branches we need to maintain the artifacts either for internal usage or external sharing
  • packages
  • docker images