Spring Boot and Kubernetes: Mastering ConfigTree Variables for Datasource Connections

Learn how to configure a datasource connection in a Spring Boot application using Kubernetes Secrets and ConfigTree variables effectively.
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Spring Boot and Kubernetes: Mastering ConfigTree Variables for Datasource Connections

In today's modern cloud-native applications, managing sensitive data securely is crucial. If you're working with a Spring Boot application, you might face challenges when trying to configure a datasource connection from a Kubernetes Secret. Due to security constraints, using environment variables via envFrom and secretRef in the Deployment descriptor may not be an option. In this guide, we’ll explore a solution using Spring’s ConfigTree imports to access your secrets effectively.

The Challenge

You have a Spring Boot application configured to utilize a PostgreSQL datasource, and you need to access the secrets contained in a Kubernetes Secret. Your deployment setup includes the following:

A mounted volume that contains sensitive information, like database credentials.

An application.yml file that references those secrets using property placeholders.

However, you encounter an error stating, "Hostname ${POSTGRES_HOST} not found." This indicates that Spring is not capable of reinterpreting the ConfigTree imported properties for other properties.

Proposed Solution

Configuring ConfigTree Imports

To effectively leverage Kubernetes Secrets in your Spring Boot application using ConfigTree, follow these steps:

Setting the ConfigTree Base Path
You’ve correctly set the config tree base path to /etc/secrets/ in your application.yml. To ensure the secrets are accessible, the associated keys must be mapped properly.

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Volume and VolumeMount Configuration
Your Kubernetes Deployment should include a volume that points to your secrets. Ensure it's correctly mounted:

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Accessing Secrets in Your Spring Boot Application

After mounting your secrets, strong ConfigTree converts the subdirectory path to a dot-separated prefix /strong on the configuration property names. Here’s how the mapping works:

The secret key POSTGRES_HOST becomes accessible as postgres.HOST.

Similarly, you can access the other values with their corresponding dot-separated names.

Updating Your Application Properties

Update your application.yml to reference the appropriate properties:

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Validating Your Configuration

To confirm the values are correctly loaded, create a ConfigurationProperties class to expose the expected properties:

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Conclusion

By following these configurations, your Spring Boot application should now be able to read and utilize the Kubernetes secret values correctly. This method provides a secure way to handle sensitive database credentials while adhering to best practices in cloud-native applications.

Should you encounter further issues, make sure to check the secrets and paths in your Kubernetes setup, and verify that they're accessible within your application context.

Embrace these techniques to manage your datasource connections securely and effectively in Spring Boot!