The intranet address of MySQL referenced in Dockerfile does not take effect. How to solve it?

The issue where the intranet address of MySQL referenced in a Dockerfile does not take effect typically occurs due to incorrect network configuration, service discovery problems, or timing issues during container startup. Here's how to solve it:

Possible Causes and Solutions:

1. Incorrect MySQL Host Address

   • The Dockerfile or application code may reference a hardcoded IP or hostname that doesn't resolve correctly in the container network.
   • Solution: Use Docker's built-in DNS or service names instead of hardcoding IPs. For example, if MySQL runs in another container, reference it by its service name (e.g., mysql).

2. Container Network Isolation

   • If MySQL and the application are in different networks, they can't communicate.
   • Solution: Ensure both containers are in the same Docker network. Create a custom network and connect both containers to it:

     docker network create my_network
     docker run --name mysql --network my_network -e MYSQL_ROOT_PASSWORD=123456 -d mysql:latest
     docker run --name app --network my_network -d your_app_image
     

3. MySQL Service Not Ready When Application Starts

   • The application may try to connect to MySQL before it's fully initialized.
   • Solution: Add a retry mechanism in the application or use a script to wait for MySQL to be ready before starting the app. For example, a simple bash script can check MySQL's availability:

     until mysqladmin ping -h mysql --silent; do
       sleep 1
     done
     

4. Environment Variables Not Passed Correctly

   • The application may rely on environment variables for the MySQL address, but they are not set properly.
   • Solution: Verify that the correct environment variables are passed to the container. For example:

     docker run -e MYSQL_HOST=mysql -e MYSQL_PORT=3306 -d your_app_image
     

5. Docker Compose Configuration

   • If using Docker Compose, ensure the services are correctly linked and the network is shared.
   • Example docker-compose.yml:

     version: '3'
     services:
       mysql:
         image: mysql:latest
         environment:
           MYSQL_ROOT_PASSWORD: 123456
       app:
         image: your_app_image
         depends_on:
           - mysql
         environment:
           MYSQL_HOST: mysql
           MYSQL_PORT: 3306
     

Using Tencent Cloud Services for MySQL in Containers:

If you're deploying this setup on Tencent Cloud, consider using Tencent Cloud Container Service (TKE) or Tencent Cloud Database for MySQL for managed MySQL instances.

• TKE: Simplifies container orchestration and networking, ensuring seamless communication between containers.
• Tencent Cloud Database for MySQL: Provides a managed MySQL service with high availability and scalability. You can connect your application containers to it using private network addresses or VPC peering.

For example, in a Tencent Cloud TKE cluster, you can deploy MySQL as a separate service and reference it by its service name in your application containers.