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How to use Docker Compose Watch for automatic code synchronization during local development?

Answer

Docker Compose Watch is a built-in tool designed to accelerate the local development cycle by automatically tracking source code changes and instantly transferring them inside a running container. The tedious necessity of constantly rebuilding the image upon every single line of code change is a thing of the past, as the tool is capable of operating in real time.

To configure this functionality, you need to edit the docker-compose.yml configuration file by adding a special watch section for each service you want to develop in interactive mode. In this section, you specify the paths to local files to monitor, as well as the behavior strategy upon detecting changes.

There are several main synchronization strategies that can be customized to the needs of a specific technology stack:

The sync mode simply copies modified files from the host machine into the working directory of the running container without restarting the process, which is ideal for interpreted languages such as JavaScript, PHP, or Python.
The rebuild mode automatically triggers a full Docker image rebuild and restarts the container if changes affected configuration files, dependencies, or build files such as package.json or requirements.txt.
The sync+restart mode copies files and restarts a specific process inside the container, which is useful for applications requiring runtime reload when source code is updated in compiled languages.

To start monitoring in the terminal, it is enough to run the standard docker compose watch command. The tool will connect to the daemon and start outputting synchronization logs, allowing you to write code in your favorite editor and see the results of changes in the browser or console almost instantly, combining the convenience of local development with container environment isolation.

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