Скачать или смотреть How to Run rails assets:precompile and Rails Server at Startup in Kubernetes Deployments

Discover how to effectively run asset compilation alongside your Rails server in a Kubernetes deployment. Follow our step-by-step guide for a seamless setup.
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How to Run rails assets:precompile and Rails Server at Startup in Kubernetes Deployments

Deploying Ruby on Rails applications on Kubernetes can sometimes lead to tricky situations, especially when it comes to executing multiple commands at startup. If you find yourself in a position where you need to compile your assets and run the Rails server at the same time, you're not alone! In this guide, we will explore an effective approach to solve this problem and ensure your Rails application runs smoothly in a Kubernetes environment.

The Problem: Running Multiple Commands

When you deploy a Rails application, the default command in your Dockerfile might look something like this:

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This command instructs Docker to start the Rails server, but it doesn't handle the asset compilation required for a production environment using the command rails assets:precompile. When you try to chain the commands together using the && operator, you encounter an error like this:

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This indicates that the shell does not recognize the command as it's not interpreting the operations correctly. Let's break down the solution to address this issue properly.

The Solution: Use an Entrypoint Script

Instead of trying to combine commands directly in the command field of your Kubernetes configuration, you can create an entrypoint script. This method allows you to execute multiple commands in a clean and organized way.

Step 1: Create the Entrypoint Script

Create a file named entrypoint.sh, and add the following content:

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This script will:

Clear any old PID files that could prevent the server from running.

Precompile the assets needed for production.

Lastly, it will execute any command passed to the container, which in this case is starting the Rails server.

Step 2: Update Your Dockerfile

Next, you'll want to modify your Dockerfile to set up the entrypoint. Add the following lines to your Dockerfile:

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Step 3: Configure Your Kubernetes Deployment

Finally, adjust your Kubernetes deployment configuration to use the updated command. Here’s an example:

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This configuration will ensure that the entrypoint script runs when the container starts, followed by the Rails server command.

The Quick and Simple Alternative

If you prefer a more straightforward approach without creating a separate script, you might also consider using a single command with bash -c. Here’s how that would look:

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This method achieves the same result but may not be as clean as using an entrypoint script, especially for complex applications.

Conclusion

Running both rails assets:precompile and the Rails server in a Kubernetes deployment is entirely possible with the right setup. Whether you choose to go with an entrypoint script for clarity and scalability or the straightforward bash command, you can ensure your Rails application is ready for production.

By following the steps outlined in this article, you can streamline your deployment process and avoid the common errors associated with running multiple startup commands.