Скачать или смотреть Why am I getting "psql: server closed the connection unexpectedly" from my Python script?

Discover why your Python script encounters a connection error with PostgreSQL in Docker, and learn a simple solution to resolve it.
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Understanding the Connection Error in PostgreSQL with Python and Docker

If you're running a Python script to interact with a PostgreSQL database deployed in a Docker container, you might encounter an error that reads:

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

This error can be frustrating, especially when things seem to work perfectly when you execute the command directly in the command line. In this post, we'll discuss why this error occurs and outline the solution in a simple, manageable way.

The Problem Explained

Your Python script utilizes the docker-py library to create a PostgreSQL Docker container as shown below:

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

This code effectively starts a PostgreSQL container. However, when you attempt to execute a PostgreSQL command via Python like this:

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

You receive an error about the server closing the connection unexpectedly. The major issue here is timing — the PostgreSQL service may not have fully started in the Docker container before your script attempts to connect to it.

Why Does This Happen?

When you run a PostgreSQL container with "detach=True", it starts in the background but does not wait for the PostgreSQL server to fully initialize before moving on to the next command in your script. As a result, your command is being executed too soon, which leads to the connection error.

The Solution: Adding a Delay

To address this issue, you'll want to ensure that your script waits for the PostgreSQL server to properly boot up before attempting any database operations. Here’s how to implement this with a simple solution:

Step-by-Step Fix

Add a Sleep Delay: After the command that starts the container, insert a sleep delay. This allows the PostgreSQL server time to initialize fully before proceeding with the execution of commands.

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

Place this line right after your container variable declaration.

Full Script Example:
Here’s your updated Python script with the necessary modifications:

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

Conclusion

By simply adding a sleep command, you're giving PostgreSQL enough time to complete its startup routine before your script tries to connect. This will prevent the "server closed the connection unexpectedly" error, allowing your database commands to execute successfully.

In summary, this approach helps you manage the timing issues often faced when automating database interactions with Docker containers. Happy coding!