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DevOps Guide: Android CI/CD with Docker

This guide explains the "Why" and "How" of this project's architecture, specifically tailored for DevOps interview preparation.

Part 1: The Architecture (Interview Concept)

Question: "How do you ensure consistent builds across different developer machines and CI servers?" Answer: "By containerizing the build environment. I use Docker to define the exact version of the JDK, Android SDK, and Build Tools. This verifies that 'it works on my machine' means it works everywhere."

The Dockerfile Explained

View Dockerfile

  • FROM eclipse-temurin:17-jdk: We start with a stable, lightweight Java base image.
  • ENV ANDROID_HOME: We adhere to standard conventions for SDK location.
  • sdkmanager: We programmatically install specific SDK versions (platform-34) matching our build.gradle config.

Part 2: The Pipeline (Interview Concept)

Question: "Describe your CI/CD strategy for mobile apps." Answer: "I implement a branching strategy where feature branches trigger flexible debug builds for rapid feedback, while the main branch triggers strict production/release builds."

The Workflow Explained

View Workflow

1. Conditional Logic

We use shell scripting within the workflow to determine the build target dynamically:

if [ "${{ github.ref }}" == "refs/heads/main" ]; then
  # Production: Build Release
  echo "TASK=assembleRelease" >> $GITHUB_OUTPUT
else
  # Development: Build Debug
  echo "TASK=assembleDebug" >> $GITHUB_OUTPUT
fi

2. Isolation

The build runs inside the Docker container:

docker run --rm -v $(pwd):/app ... ./gradlew $TASK

This ensures the CI runner's pre-installed tools don't interfere with our build.

3. Artifact Retention

We use actions/upload-artifact to save the correct APK (app-debug.apk or app-release-unsigned.apk) allowing QA teams to download and test immediately without access to the code.

Part 3: Android Configuration Basics for DevOps

Question: "What files do you need to configure in an Android project?" Answer:

  1. app/build.gradle: Defines the compileSdk (must match Dockerfile) and versionCode (should be auto-incremented in CI).
  2. gradle.properties: Controls build performance (JVM args) and library compatibility (android.useAndroidX=true).
  3. local.properties: IGNORED by git. Used for local SDK paths. In CI, we use environment variables instead.

Part 4: Common Interview Troubleshooting

  • "Gradle not found": Often means the wrapper script (gradlew) relies on a system gradle that isn't installed. Fix: Install Gradle in the Docker image or use the wrapper correctly.
  • "Permission denied": gradlew script often loses executable permission in git. Fix: chmod +x gradlew or git update-index --chmod=+x.
  • "License not accepted": The Android SDK requires explicit license acceptance. Fix: Run yes | sdkmanager --licenses in the Dockerfile.