"MySQL woes in GitHub Actions: A Guide to Accessing Your Database"
The Problem: You've diligently created a MySQL database in your GitHub Actions workflow, but when your code tries to connect, you're met with a frustrating "Connection refused" error. This can leave you scratching your head, wondering why your workflow can't access the very database it just created.
Scenario: Let's imagine you're building a Node.js application that interacts with a MySQL database. You've set up a GitHub Actions workflow that spins up a MySQL server using a Docker container, creates your database, and runs your application's tests. But when your application tries to connect to the database, it fails.
Original Code:
name: MySQL Testing
on:
push:
branches:
- master
jobs:
test:
runs-on: ubuntu-latest
steps:
- name: Checkout code
uses: actions/checkout@v2
- name: Start MySQL container
uses: docker/build-push-action@v2
with:
context: .
file: Dockerfile
push: false
- name: Run MySQL commands
run: |
docker exec -it mysql-container mysql -u root -p'password' -e "CREATE DATABASE my_test_db;"
- name: Run application tests
run: npm test
Analysis: The issue lies in the way we're attempting to connect to the database. The docker exec command, while running the mysql command inside the container, doesn't establish a persistent connection for your application to use.
Here's the Breakdown:
- Container Isolation: Docker containers are inherently isolated environments. Your application running within a separate container or directly on the runner's machine cannot directly connect to services within the MySQL container.
- Ephemeral Connection: The
docker execcommand creates a temporary connection for executing the SQL statement. This connection doesn't survive after the command execution.
Solution: To solve this, we need to use a mechanism that provides a persistent connection between your application and the MySQL container. One common approach is to use a network bridge that allows containers to communicate with each other.
Revised Workflow:
name: MySQL Testing
on:
push:
branches:
- master
jobs:
test:
runs-on: ubuntu-latest
steps:
- name: Checkout code
uses: actions/checkout@v2
- name: Start MySQL container
uses: docker/build-push-action@v2
with:
context: .
file: Dockerfile
push: false
- name: Create database
run: |
docker exec -it mysql-container mysql -u root -p'password' -e "CREATE DATABASE my_test_db;"
- name: Run application tests
# Use your environment variables for database connection
env:
DB_HOST: mysql-container
DB_PORT: 3306
DB_USER: root
DB_PASSWORD: 'password'
DB_NAME: my_test_db
run: npm test
Explanation:
- Network Bridge: The Dockerfile for your MySQL container should define a network bridge, typically called
mysql-network. This network allows communication between your application container and the MySQL container. - Environment Variables: Define environment variables within your application's test environment that specify the database connection details. This ensures your application knows where to connect.
- Connecting to the database: Your application code will need to use these environment variables to establish a connection to the database.
Additional Tips:
- Persistence: If you need your database to persist between workflow runs, consider using a persistent volume.
- Securing Credentials: Avoid storing your database credentials in plain text in your workflow file. Use secrets for storing sensitive information securely.
Conclusion: By understanding the limitations of container isolation and using a network bridge for communication, you can reliably access your MySQL database within your GitHub Actions workflows. Remember to secure your credentials and choose the appropriate persistence solution for your needs.
References:
