Using Spring Cloud Config Server for Multi-tenancy configuration

Let's walk through a basic example of how to set up and use Spring Cloud Config Server to manage configuration for multiple tenants in a Spring Boot Application.

Step 1: Create a Spring Cloud Config Server

Create a new Spring Boot project with the Spring Cloud Config Server dependency.

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

Configure the Spring Cloud Config Server:

// src/main/java/com/example/ConfigServerApplication.java
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.config.server.EnableConfigServer;

@SpringBootApplication
@EnableConfigServer
public class ConfigServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(ConfigServerApplication.class, args);
    }
}

Configure the application properties to specify the Git repository where configuration files are stored:

# src/main/resources/application.yml
spring:
  cloud:
    config:
      server:
        git:
          uri: <URL to your Git repository>

Step 2: Create Configuration Files for Tenants

In your Git repository, organize configuration files based on tenants and profiles:

 config-repo/
|-- application-tenant1.properties
|-- application-tenant2.properties
|-- application.yml

Example content for application-tenant1.properties:

# application-tenant1.properties
greeting.message=Hello from Tenant 1!

Example content for application-tenant2.properties:

# application-tenant2.properties
greeting.message=Hello from Tenant 2!

Step 3: Create a Spring Boot Application

Create a new Spring Boot project for the multi-tenant application:

<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <!-- Other dependencies -->
</dependencies>

Configure the application to use the Spring Cloud Config Client:

# src/main/resources/bootstrap.yml 
spring:
  application:
    name: myapp
  cloud:
    config:
      uri: http://localhost:8888 # URL to your Config Server

Create a controller to retrieve the configuration property:

// src/main/java/com/example/MyAppController.java
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyAppController {
    @Value("${greeting.message}")
    private String greetingMessage;

    @GetMapping("/greeting")
    public String getGreetingMessage() {
        return greetingMessage;
    }
}

Step 4: Test the Application

1. Start the Spring Cloud Config Server application.
2. Start the multi-tenant Spring Boot application.
3. Access the greeting message for each tenant using the /greeting endpoint:
   1. For Tenant 1: http://localhost:8080/greeting
   2. For Tenant 2: http://localhost:8080/greeting

The Spring Cloud Config Server will provide the appropriate configuration properties based on the tenant-specific profile used in the application. This example demonstrates a basic setup of using Spring Cloud Config Server to manage configuration for multiple tenants in a Spring Boot application.

Dynamic Tenant identification - Simple approach

To dynamically load the configuration for different tenants based on a URL parameter or path segment, you can use Spring Cloud Config's native support for profiles and the application name to achieve this. Here's how you can modify the configuration to achieve dynamic loading of tenant-specific configurations:

Below given is a sample yaml configuration that can be used to dynamically identify the tenant

# src/main/resources/bootstrap.yml
spring:
  cloud:
    config:
      uri: http://localhost:8888
  application:
    name: myapp # The base application name
  profiles:
    active: @tenant # Placeholder for the active profile

    

Tenant Identification from URL

// src/main/java/com/example/MyAppController.java
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyAppController {
    @Value("${greeting.message}")
    private String greetingMessage;

    @GetMapping("/greeting/{tenant}")
    public String getGreetingMessage(@PathVariable String tenant) {
        // Set the active profile dynamically based on the tenant
        System.setProperty("spring.profiles.active", tenant);
        try {
            // Business logic using the tenant-specific profile
            return greetingMessage;
        } finally {
            // Clean up the active profile to avoid affecting subsequent requests
            System.clearProperty("spring.profiles.active");
        }
    }
}
  

Access Configuration via URL Path:

Now you can access the tenant-specific configuration by specifying the tenant as a path segment in the URL. For example:

1. For Tenant 1: http://localhost:8080/greeting/tenant1
2. For Tenant 2: http://localhost:8080/greeting/tenant2

Each URL will dynamically set the active profile based on the tenant, and the Spring Cloud Config Server will serve the corresponding tenant-specific configuration properties.