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Travis CI Cheat Sheet

A comprehensive cheat sheet covering essential Travis CI configurations, commands, and best practices for continuous integration and deployment.

Core Concepts & Configuration

Basic `.travis.yml` Structure

A basic .travis.yml file specifies the language and build steps:

language: ruby
rvm:
  - 2.7
before_install:
  - gem install bundler
install:
  - bundle install
script:
  - bundle exec rspec

Key components:

  • language: Specifies the programming language.
  • rvm (or equivalent): Specifies the version manager and versions.
  • before_install: Commands to run before installing dependencies.
  • install: Commands to install dependencies.
  • script: Commands to run the build/test suite.

Language Support

language: ruby

Specifies the Ruby language environment.

language: node_js

Specifies the Node.js environment.

language: python

Specifies the Python environment.

language: java

Specifies the Java environment.

Build Lifecycle Stages

Travis CI build lifecycle consists of distinct stages:

  • before_install: Prepare the environment.
  • install: Install dependencies.
  • before_script: Run commands before the main script.
  • script: Run the primary build script (tests, etc.).
  • after_success / after_failure: Commands to run based on the script’s success.
  • after_script: Always runs regardless of build outcome.
  • before_deploy: Run before deploying code.
  • deploy: Deploy the code to a provider.
  • after_deploy: Run commands after successful deployment.

Advanced Configuration

Environment Variables

env:

Define environment variables for the build. Can be global or matrix-specific.

env:
  global:
    - secure: ENCRYPTED_PASSWORD
  matrix:
    - TEST_SUITE=unit
    - TEST_SUITE=integration

Secure Variables

Sensitive data should be encrypted using the Travis CI CLI and stored as secure: variables.

Build Matrix

A build matrix allows you to test your code against multiple configurations.

matrix:
  include:
    - rvm: 2.6
      gemfile: gemfiles/rails-5.2.gemfile
    - rvm: 2.7
      gemfile: gemfiles/rails-6.0.gemfile

You can exclude specific configurations:

matrix:
  exclude:
    - rvm: 2.5
      gemfile: gemfiles/rails-6.0.gemfile

Caching Dependencies

cache:

Enable caching to speed up builds by reusing dependencies.

cache:
  directories:
    - node_modules
    - vendor/bundle

Common directories

node_modules, vendor/bundle, and other dependency directories can be cached.

Deployment

Basic Deployment Configuration

Travis CI supports deployment to various providers. Here’s an example for deploying to Heroku:

deploy:
  provider: heroku
  api_key:
    secure: ENCRYPTED_HEROKU_API_KEY
  app: your-heroku-app-name
  on:
    branch: master

Key components:

  • provider: Specifies the deployment provider.
  • api_key: Your API key for the provider (encrypted).
  • app: The name of your application on the provider.
  • on: Conditions for deployment (e.g., branch).

Conditional Deployment

on: branch: master

Deploys only when the build is triggered from the master branch.

on: tags: true

Deploys only when a tagged commit is built.

Deployment Providers

Travis CI supports a wide range of deployment providers, including:

  • Heroku
  • AWS (S3, Elastic Beanstalk)
  • Firebase
  • GitHub Pages
  • PyPI
  • npm
  • and many more.

Tips and Tricks

Debugging Travis CI Builds

Debugging failed builds:

  • Check the Travis CI build logs for error messages.
  • Enable debug mode by setting travis_debug: true in your .travis.yml.
  • Use SSH access for interactive debugging (requires a paid plan).
  • Add echo statements in your .travis.yml to print variable values and execution flow.

Optimizing Build Times

Caching

Cache dependencies to reduce installation time.

Parallelization

Run tests in parallel using tools like parallel_test (for Ruby) or tox (for Python).

Selective Testing

Run only the necessary tests based on changed files.

Common Issues and Solutions

Common issues:

  • Incorrect rvm or language version.
  • Missing dependencies.
  • Test failures due to environment differences.
  • Deployment failures due to incorrect credentials.

Solutions:

  • Double-check your .travis.yml configuration.
  • Ensure all dependencies are listed in your dependency management file (e.g., Gemfile, package.json).
  • Use environment variables to handle sensitive data.
  • Test your deployment process locally before pushing to Travis CI.
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