Скачать или смотреть How to Effectively Manage Postgres Containers on Different Ports with Docker

Discover how to run multiple `Postgres` containers using `Docker` and `docker-compose` on different ports, while ensuring seamless connections from your terminal.
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This video is based on the question https://stackoverflow.com/q/68622071/ asked by the user 'Alexander Slesarev' ( https://stackoverflow.com/u/9139429/ ) and on the answer https://stackoverflow.com/a/68622274/ provided by the user 'David Maze' ( https://stackoverflow.com/u/10008173/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing Postgres Containers on Different Ports with Docker

Running multiple instances of PostgreSQL in Docker containers can be a bit of a challenge, especially when trying to connect them to specific ports. In this post, we’ll break down how to achieve this using docker-compose. If you've previously faced connection issues or confusion regarding port mapping, this guide is for you!

Understanding the Problem

The problem arises when trying to connect to your PostgreSQL containers from the terminal. By default, PostgreSQL listens on port 5432. If you have multiple containers set up, you'll need to change the port mapping to avoid conflicts and make connecting straightforward. The key is to specify the ports correctly in your docker-compose.yml file.

Step-by-Step Solution

Let's walk through a well-structured approach to solve the port matching issue when running multiple PostgreSQL containers.

1. Define Your docker-compose.yml

Your first step is to create a docker-compose.yml file that lists each PostgreSQL container and defines the ports correctly. Here's how you should set it up:

[[See Video to Reveal this Text or Code Snippet]]

2. Port Mapping Explained

The first number in the ports mapping is the host port that you will use to connect to the container.

The second number is the container port where PostgreSQL is running (which will always be 5432).

3. Connecting to Your PostgreSQL Containers

Once your docker-compose.yml file is set up, you can connect to your PostgreSQL containers from your terminal using the psql command. Here’s how you do it for each container:

To connect to pg1:

[[See Video to Reveal this Text or Code Snippet]]

To connect to pg2:

[[See Video to Reveal this Text or Code Snippet]]

4. Avoid Common Confusions

You do not need to include an expose: directive in your docker-compose.yml, as it doesn’t alter connectivity directly for the purpose of this setup.

Incorrect address connection: Using localhost is correct when connecting via the host. Using 0.0.0.0 as a host address is not necessary as it refers to all interfaces and might lead to confusion while trying to connect.

5. Connecting from Another Container

When you're connecting from one container to another (e.g., going from pg1 to pg2), you only need to use the service name. There’s no need for port mappings in this case. The connection can be made like so:

[[See Video to Reveal this Text or Code Snippet]]

Docker Compose automatically sets up a network that allows containers to communicate seamlessly with each other.

Conclusion

Configuring multiple PostgreSQL containers in Docker may seem intimidating at first, but with the right understanding of port mapping and connection strings, it becomes manageable. Be sure to run your psql commands with the correct parameters based on your configuration, and you’ll be able to link your terminal to each PostgreSQL instance efficiently.

By following this structured guide, you can ensure that your PostgreSQL containers do not conflict and can be easily accessed from your terminal. Happy coding!