Configure settings for the Eureka Server for Spring component in Azure Container Apps

Eureka Server for Spring is mechanism for centralized service discovery for microservices. Use the following guidance to learn how to configure and manage your Eureka Server for Spring component.

Show

You can view the details of an individual component by name using the show command.

Before you run the following command, replace placeholders surrounded by <> with your values.

az containerapp env java-component eureka-server-for-spring show \
  --environment <ENVIRONMENT_NAME> \
  --resource-group <RESOURCE_GROUP> \
  --name <JAVA_COMPONENT_NAME>

List

You can list all registered Java components using the list command.

Before you run the following command, replace placeholders surrounded by <> with your values.

az containerapp env java-component list \
  --environment <ENVIRONMENT_NAME> \
  --resource-group <RESOURCE_GROUP>

Unbind

To remove a binding from a container app, use the --unbind option.

Before you run the following command, replace placeholders surrounded by <> with your values.

az containerapp update \
  --name <APP_NAME> \
  --unbind <JAVA_COMPONENT_NAME> \
  --resource-group <RESOURCE_GROUP>

Allowed configuration list for your Eureka Server for Spring

The following list details supported configurations. You can find more details in Spring Cloud Eureka Server.

Configuration options

The az containerapp update command uses the --configuration parameter to control how the Eureka Server for Spring is configured. You can use multiple parameters at once as long as they're separated by a space. You can find more details in Spring Cloud Eureka Server docs.

The following configuration settings are available on the eureka.server configuration property.

Common configurations

• logging related configurations
  • logging.level.*
  • logging.group.*
  • Any other configurations under logging.* namespace should be forbidden, for example, writing log files by using logging.file should be forbidden.

Call between applications

This example shows you how to write Java code to call between applications registered with the Eureka Server for Spring component. When container apps are bound with Eureka, they communicate with each other through the Eureka server.

The example creates two applications, a caller and a callee. Both applications communicate among each other using the Eureka Server for Spring component. The callee application exposes an endpoint that is called by the caller application.

1. Create the callee application. Enable the Eureka client in your Spring Boot application by adding the @EnableDiscoveryClient annotation to your main class.

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

2. Create an endpoint in the callee application that is called by the caller application.

   @RestController
   public class CalleeController {
   
       @GetMapping("/call")
       public String calledByCaller() {
           return "Hello from Application callee!";
       }
   }
   

3. Set the callee application's name in the application configuration file. For example, application.yml.

   spring.application.name=callee
   

4. Create the caller application.

   Add the @EnableDiscoveryClient annotation to enable Eureka client functionality. Also, create a WebClient.Builder bean with the @LoadBalanced annotation to perform load-balanced calls to other services.

   @SpringBootApplication
   @EnableDiscoveryClient
   public class CallerApplication {
       public static void main(String[] args) {
           SpringApplication.run(CallerApplication.class, args);
       }
   
       @Bean
       @LoadBalanced
       public WebClient.Builder loadBalancedWebClientBuilder() {
           return WebClient.builder();
       }
   }
   

5. Create a controller in the caller application that uses the WebClient.Builder to call the callee application using its application name, callee.

   @RestController
   public class CallerController { 
       @Autowired
       private WebClient.Builder webClientBuilder;
   
       @GetMapping("/call-callee")
       public Mono<String> callCallee() {
           return webClientBuilder.build()
               .get()
               .uri("http://callee/call")
               .retrieve()
               .bodyToMono(String.class);
       }
   }
   

Now you have a caller and callee application that communicate with each other using Eureka Server for Spring Java components. Make sure both applications are running and bind with the Eureka server before testing the /call-callee endpoint in the caller application.

Limitations

• The Eureka Server Java component comes with a default configuration, eureka.server.enable-self-preservation, set to false. This default configuration helps avoid times when instances aren't deleted after self-preservation is enabled. If instances are deleted too early, some requests might be directed to nonexistent instances. If you want to change this setting to true, you can overwrite it by setting your own configurations in the Java component.

• The Eureka server has only a single replica and doesn't support scaling, making the peer Eureka server feature unavailable.

• The Eureka dashboard isn't available.

Next steps