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Spring Cloud Netflix: Circuit Breaking Metric Aggregation

Estimated Time: 25 minutes

Requirements

Lab Requirements

What You Will Learn

  • How to aggregate multiple metric streams with turbine
  • How to use Turbine in Pivotal Cloud Foundry

Exercises

Start the config-server, service-registry, fortune-service, greeting-hystrix, and hystrix-dashboard applications

  1. Start the config-server in a terminal window. You may have terminal windows still open from previous labs. They may be reused for this lab.
$ cd $CLOUD_NATIVE_APP_LABS_HOME/config-server
$ mvn clean spring-boot:run
  1. Start the service-registry
$ cd $CLOUD_NATIVE_APP_LABS_HOME/service-registry
$ mvn clean spring-boot:run
  1. Start the fortune-service
$ cd $CLOUD_NATIVE_APP_LABS_HOME/fortune-service
$ mvn clean spring-boot:run
  1. Start the greeting-hystrix
$ cd $CLOUD_NATIVE_APP_LABS_HOME/greeting-hystrix
$ mvn clean spring-boot:run
  1. Start the hystrix-dashboard
$ cd $CLOUD_NATIVE_APP_LABS_HOME/hystrix-dashboard
$ mvn clean spring-boot:run

Allow a few moments for greeting-hystrix and fortune-service to register with the service-registry.

Set up turbine

Looking at individual application instances in the Hystrix Dashboard is not very useful in terms of understanding the overall health of the system. Turbine is an application that aggregates all of the relevant /hystrix.stream endpoints into a combined /turbine.stream for use in the Hystrix Dashboard.

  1. Review the $CLOUD_NATIVE_APP_LABS_HOME/turbine/pom.xml file. By adding spring-cloud-starter-turbine to the classpath this application is eligible to aggregate metrics via Turbine.
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-turbine</artifactId>
</dependency>
  1. Review the following file: $CLOUD_NATIVE_APP_LABS_HOME/turbine/src/main/java/io/pivotal/TurbineApplication.java. Note the use of the @EnableTurbine annotation. This creates a turbine application.
@SpringBootApplication
@EnableTurbine
public class TurbineApplication {


    public static void main(String[] args) {
        SpringApplication.run(TurbineApplication.class, args);
    }

}

3). Review the following file: $CLOUD_NATIVE_APP_LABS_HOME/turbine/src/main/resources/bootstrap.yml. turbine.appConfig is a list of Eureka serviceIds that Turbine will use to lookup instances. turbine.aggregator.clusterConfig is the Turbine cluster these services belong to (how they will be grouped).

spring:
  application:
    name: turbine
  cloud:
    config:
      uri: ${vcap.services.config-server.credentials.uri:http://localhost:8888}
turbine:
  aggregator:
    clusterConfig: GREETING-HYSTRIX
  appConfig: greeting-hystrix
  1. Open a new terminal window. Start the turbine app
$ cd $CLOUD_NATIVE_APP_LABS_HOME/turbine
$ mvn clean spring-boot:run

  1. Wait for the turbine application to register with service-registry.

  2. View the turbine stream in a browser http://localhost:8585/turbine.stream?cluster=GREETING-HYSTRIX turbine-stream

  3. Configure the hystrix-dashboard to consume the turbine stream. Enter http://localhost:8585/turbine.stream?cluster=GREETING-HYSTRIX

  4. Experiment! Refresh the greeting-hystrix / endpoint several times. Take down the fortune-service app. What does the dashboard do?

  5. When done, stop the config-server, service-registry, fortune-service, greeting-hystrix, hystrix-dashboard and turbine applications.

What Just Happened?

Turbine discovered the greeting-hystrix application through the service-registry application. Turbine then consumed the /hystrix.stream and rolled that up into an aggregate /turbine.stream. Therefore, if we had multiple greeting-hystrix applications running all the metrics could be consumed from this single endpoint (/turbine.stream)

Deploying to PCF

In PCF, the traditional Turbine model of pulling metrics from all the distributed Hystrix enabled applications doesn’t work. This is because every application has the same hostname (every app instance has the same URL for a given app). The problem is solved with Turbine AMQP. Metrics are published through a message broker. We'll use RabbitMQ.

Deploy greeting-hystrix to PCF

  1. Add the following dependency to the $CLOUD_NATIVE_APP_LABS_HOME/greeting-hystrix/pom.xml file. You must edit the file.
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-netflix-hystrix-amqp</artifactId>
</dependency>
  1. Create a RabbitMQ Service Instance on PCF
$ cf create-service p-rabbitmq standard turbine-broker
  1. Package, push, bind services and set environment variables for greeting-hystrix.
$ mvn clean package
$ cf push greeting-hystrix -p target/greeting-hystrix-0.0.1-SNAPSHOT.jar -m 512M --random-route --no-start
$ cf bind-service greeting-hystrix config-server
$ cf bind-service greeting-hystrix turbine-broker
$ cf set-env greeting-hystrix SPRING_PROFILES_ACTIVE dev
$ cf start greeting-hystrix

You can safely ignore the TIP: Use 'cf restage' to ensure your env variable changes take effect message from the CLI. We can just start the greeting-hystrix application.

Deploy turbine-amqp to PCF

  1. Review the $CLOUD_NATIVE_APP_LABS_HOME/turbine-amqp/pom.xml file. By adding spring-cloud-starter-turbine-amqp to the classpath this application is eligible to use Turbine AMQP.
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-turbine-amqp</artifactId>
</dependency>
  1. Review the following file: $CLOUD_NATIVE_APP_LABS_HOME/turbine-amqp/src/main/java/io/pivotal/TurbineApplication.java. Note the use of the @EnableTurbineAmqp annotation. This creates a turbine application. Turbine AMQP uses com.netflix.turbine:turbine-core:2.0.0-DP.2 which leverages Netty, so we turn off our servlet container (Tomcat).
@SpringBootApplication
@EnableTurbineAmqp
public class TurbineApplication {

    public static void main(String[] args) {
		new SpringApplicationBuilder(TurbineApplication.class).web(false).run(args);
	}


}

3). Review the following file: $CLOUD_NATIVE_APP_LABS_HOME/turbine-amqp/src/main/resources/bootstrap.yml. turbine.appConfig and turbine.aggregator.clusterConfig no longer need to be configured.

spring:
  application:
    name: turbine-amqp
  cloud:
    config:
      uri: ${vcap.services.config-server.credentials.uri:http://localhost:8888}
  1. Package, push and bind services for turbine-amqp
$ mvn clean package
$ cf push turbine-amqp -p target/turbine-amqp-0.0.1-SNAPSHOT.jar --random-route -m 512M --no-start
$ cf bind-service turbine-amqp turbine-broker
$ cf start turbine-amqp

You can safely ignore the TIP: Use 'cf restage' to ensure your env variable changes take effect message from the CLI. We can just start the turbine-amqp application.

Deploy hystrix-dashboard to PCF

  1. Package, and push hystrix-dashboard
$ mvn clean package
$ cf push hystrix-dashboard -p target/hystrix-dashboard-0.0.1-SNAPSHOT.jar -m 512M --random-route

  1. Configure the hystrix-dashboard (i.e http://your-hystrix-url/hystrix) to consume the turbine stream. Enter your turbine-amqp URL.

  2. Experiment! Refresh the greeting-hystrix / endpoint several times. Take down the fortune-service app. Scale the greeting-hystrix app. What does the dashboard do?