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Discover how to effectively automate your Docker build and deployment processes using bash scripts. This guide tackles common issues like running npm commands and database migrations within containers.
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This video is based on the question https://stackoverflow.com/q/64283027/ asked by the user 'ViaTech' ( https://stackoverflow.com/u/8382028/ ) and on the answer https://stackoverflow.com/a/64285734/ 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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Automating Docker Build and Deploy with a Bash Script: A Complete Guide

Deploying applications using Docker can sometimes seem daunting, especially when it involves running multiple commands in sequence and ensuring that everything is set up correctly. In this guide, we will tackle a common problem faced by many developers: how to automate Docker build and deployment processes using a Bash script. We will break down the necessary steps and provide clear solutions to streamline your workflow.

The Challenge: Complex Deployment Script

You may already have a script in place for deployment, but as many developers discover, it can be challenging to get it all right in one go. For instance, when your script requires running certain commands, like npm install and database migrations, directly in a Docker container, you may find yourself struggling with how to proceed through the process without entering an interactive bash session.

The Existing Script

Here is an example of a deployment script that could use some improvement:

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Understanding the Solution

To achieve a fluent workflow with Docker, we need to address a few key points. Let's break them down:

1. Docker Best Practices

Self-contained Images: Typically, a Docker image should be self-sufficient. This means that it should know how to launch itself without needing user intervention.

Avoid Interactive Shells: Using docker-compose run to get into interactive shells for post-deployment tasks is typically discouraged. Instead, you can run commands directly with Docker features.

2. Managing Node Packages

Instead of running npm install during deployment, you should encapsulate the installation of your Node packages into your Docker image itself. Here is how you can modify your Dockerfile:

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With this setup:

Your dependencies are included in the image.

If changes are made to your package.json, running docker-compose build will trigger an npm install automatically.

3. Handling Database Migrations

Database migrations can be tricky since they cannot be executed during the image build phase. Here are two effective approaches:

Approach 1: Automatic Migrations on Startup

Create an entrypoint script to run migrations each time the container starts:

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Set this script to be executable and use it as the Docker image’s ENTRYPOINT. This way, every time the container is launched, it will perform migrations first before starting the application.

Approach 2: Manual Migration Command

If you prefer manual migration control, you can run migrations separately as follows:

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4. Upgrade Sequence with Minimal Downtime

Docker images are immutable, which allows you to build new images while existing ones run without interruption. A seamless upgrade workflow should look like this:

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Conclusion

By restructuring your deployment script according to best practices, you can achieve a more efficient and reliable Docker deployment process. Rather than entering an interactive bash shell, rely on your Docker image and scripts to handle installation and migrations without manual intervention.

Remember, mastering these automation processes saves you time and reduces errors, allowing you to focus more on building great applications!