Spring Cloud Config: Choosing the Right Backend Storage

Spring Cloud Config offers a flexible way to manage your application’s configuration. A crucial step is selecting the right backend to store your configuration data. Let’s explore popular options, their pros and cons, configuration details, and the necessary dependencies for Maven and Gradle.

1. Git

Pros:

• Version Control: Leverage Git’s robust versioning capabilities to track changes, revert to previous configurations, and manage different environments (dev, test, prod) through branches or tags.
• Familiar Workflow: Developers are likely already comfortable with Git, making it easy to adopt.
• Wide Tooling Support: Benefit from a rich ecosystem of Git tools for managing and visualizing your configuration data.

Cons:

• Performance: Fetching configurations from a remote Git repository can introduce latency, especially for large repositories or frequent updates.
• Security: Securely managing access to your Git repository is crucial, especially if it contains sensitive information.

Configuration:

By default, Spring Cloud Config uses Git. To configure it, specify the URI of your Git repository in your application.properties or application.yml file:

spring:
  cloud:
    config:
      server:
        git:
          uri: https://github.com/your-org/your-config-repo.git

Authentication:

If your Git repository is private, you’ll need to provide authentication credentials. Here are a few common approaches:

• Username and Password:

spring:
  cloud:
    config:
      server:
        git:
          uri: https://github.com/your-org/your-config-repo.git
          username: your-github-username
          password: your-github-password 

Important Note: Using plain text passwords is generally discouraged. Consider using SSH keys or access tokens for better security.

• SSH Keys:

  • Generate an SSH key pair.
  • Add the public key to your Git repository’s deploy keys or access keys.
  • Configure Spring Cloud Config to use the private key:

spring:
  cloud:
    config:
      server:
        git:
          uri: git@github.com:your-org/your-config-repo.git
          privateKey: |
            -----BEGIN RSA PRIVATE KEY-----
            ... your private key content ...
            -----END RSA PRIVATE KEY-----

• Access Tokens:

  • Generate a personal access token (PAT) in your Git provider settings with appropriate read permissions.
  • Use the PAT as the password in your configuration:

spring:
  cloud:
    config:
      server:
        git:
          uri: https://github.com/your-org/your-config-repo.git
          username: your-github-username
          password: your-github-access-token

Dependencies:

This is usually included by default in Spring Cloud Config Server starters, but if you need to add it explicitly:

Maven:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-config-server</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.cloud:spring-cloud-config-server'

2. File System

Pros:

• Simplicity: Easy to set up and use, especially for local development or simple deployments.
• Performance: Reading configurations from the local file system is generally faster than fetching from a remote repository.

Cons:

• Scalability: Not ideal for large-scale deployments or distributed systems.
• Version Control: Lacks the built-in versioning capabilities of Git. You’ll need to implement your own versioning strategy.

Configuration:

To use the file system backend, set the spring.cloud.config.server.native.search-locations property to the directory containing your configuration files:

spring:
  cloud:
    config:
      server:
        native:
          search-locations: file:///path/to/your/config/directory

Dependencies:

No specific dependency is required for the file system backend, as it’s included in the Spring Cloud Config Server.

3. Vault

Pros:

• Enhanced Security: Vault provides robust security features like encryption, access control policies, and audit logging, making it ideal for sensitive configuration data.
• Secrets Management: Vault can manage not only application configuration but also secrets like API keys, database credentials, and certificates.

Cons:

• Complexity: Setting up and managing Vault can be more complex than other options.
• Dependency: Introduces an external dependency on HashiCorp Vault.

Configuration:

To enable Vault support, add the vault profile to your configuration and provide the necessary Vault connection details:

spring:
  profiles:
    active: vault
  cloud:
    config:
      server:
        vault:
          host: your-vault-host
          port: 8200
          scheme: https
          authentication: TOKEN # or other supported authentication methods
          token: your-vault-token

Dependencies:

Maven:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.vault</groupId>
    <artifactId>spring-vault-core</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.cloud:spring-cloud-starter-config'
implementation 'org.springframework.vault:spring-vault-core'

4. Database (JDBC)

Pros:

• Centralized Management: Store configurations in a relational database, leveraging its features for data management and access control.
• Integration: Easily integrates with existing database infrastructure.

Cons:

• Performance: Database queries can be slower than accessing files or Git repositories.
• Schema Management: Requires defining and managing a database schema for your configuration data.

Configuration:

Configure a datasource and set the spring.cloud.config.server.jdbc.sql property to the SQL query used to fetch configuration data:

spring:
  cloud:
    config:
      server:
        jdbc:
          sql: SELECT key, value FROM properties WHERE application=? AND profile=? AND label=?

Dependencies:

Maven:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-config-server</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.cloud:spring-cloud-config-server'
implementation 'org.springframework.boot:spring-boot-starter-jdbc'
// Add your database driver dependency here (e.g., MySQL, PostgreSQL) 

5. AWS Parameter Store and Secrets Manager

AWS offers two primary services for managing configuration data and secrets:

• AWS Parameter Store: A hierarchical key-value store for configuration data, offering features like versioning, encryption, and integration with AWS IAM for access control.

• AWS Secrets Manager: Specifically designed for storing and rotating secrets like database credentials and API keys. It provides features like automatic rotation, fine-grained access control, and auditing.

Pros:

• Integration with AWS Ecosystem: Seamlessly integrates with other AWS services and leverages AWS’s security and scalability.
• Managed Service: Reduces operational overhead by offloading management tasks to AWS.
• Cost-Effective: Pay-as-you-go pricing model.

Cons:

• Vendor Lock-in: Ties your configuration management to AWS.

Dependencies:

Maven:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-aws-parameter-store-config</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-aws-secrets-manager-config</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.cloud:spring-cloud-starter-aws-parameter-store-config'
// or 
implementation 'org.springframework.cloud:spring-cloud-starter-aws-secrets-manager-config'

6. Azure App Configuration

Azure App Configuration is a fully managed service for centralizing application settings and feature flags.

Pros:

• Feature Management: Provides robust feature flag management capabilities, allowing you to enable or disable features in real-time.
• High Availability and Scalability: Designed for high availability and can scale to handle large volumes of requests.
• Integration with Azure Ecosystem: Integrates with other Azure services like Azure Key Vault for secrets management.

Cons:

• Vendor Lock-in: Ties your configuration management to Azure.

Dependencies:

Maven:

<dependency>
    <groupId>com.azure.spring</groupId>
    <artifactId>azure-spring-cloud-appconfiguration-config</artifactId>
</dependency>

Gradle:

implementation 'com.azure.spring:azure-spring-cloud-appconfiguration-config'