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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 $SPRING_CLOUD_SERVICES_LABS_HOME/config-server
$ mvn clean spring-boot:run
  1. Start the service-registry
$ cd $SPRING_CLOUD_SERVICES_LABS_HOME/service-registry
$ mvn clean spring-boot:run
  1. Start the fortune-service
$ cd $SPRING_CLOUD_SERVICES_LABS_HOME/fortune-service
$ mvn clean spring-boot:run
  1. Start the greeting-hystrix
$ cd $SPRING_CLOUD_SERVICES_LABS_HOME/greeting-hystrix
$ mvn clean spring-boot:run
  1. Start the hystrix-dashboard
$ cd $SPRING_CLOUD_SERVICES_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 $SPRING_CLOUD_SERVICES_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: $SPRING_CLOUD_SERVICES_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: $SPRING_CLOUD_SERVICES_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
turbine:
  aggregator:
    clusterConfig: GREETING-HYSTRIX
  appConfig: greeting-hystrix
  1. Open a new terminal window. Start the turbine app
$ cd $SPRING_CLOUD_SERVICES_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 via HTTP doesn’t work when using the route registrationMethod. Read here for more details on registration methods.

When applications register using the route method every application has the same hostname (every app instance has the same URL for a given app). Therefore it is unknown from Turbine perspective if all metrics are properly being collected. The problem is solved with Turbine AMQP. Metrics are published through a message broker. We'll use RabbitMQ.

Deploy greeting-hystrix to PCF

  1. Create a Circuit Breaker Dashboard Service Instance
$ cf create-service p-circuit-breaker-dashboard standard circuit-breaker-dashboard

When creating a Circuit Breaker Service instance there are three items that get provisioned:

  1. Hystrix Dashboard application instance
  2. Turbine AMQP application instance
  3. RabbitMQ Service Instance

This process takes some time and won't be immediately available for binding. Give it a couple of minutes.

Click on the Manage link for the circuit-breaker-dashboard service instance to determine when the circuit-breaker-dashboard service instance is ready. manage

  1. Package and push the greeting-hystrix application.
$ mvn clean package
$ cf push greeting-hystrix -p target/greeting-hystrix-0.0.1-SNAPSHOT.jar -m 512M --random-route --no-start
  1. Bind services for the greeting-hystrix.
$ cf bind-service greeting-hystrix config-server
$ cf bind-service greeting-hystrix service-registry
$ cf bind-service greeting-hystrix circuit-breaker-dashboard

You can safely ignore the TIP: Use 'cf restage' to ensure your env variable changes take effect message from the CLI. We don't need to restage at this time.

  1. If using self signed certificates, set the CF_TARGET environment variable for the greeting-hystrix application.
$ cf set-env greeting-hystrix CF_TARGET <your api endpoint - make sure it starts with "https://">

You can safely ignore the TIP: Use 'cf restage' to ensure your env variable changes take effect message from the CLI. We don't need to restage at this time.

  1. Start the greeting-hystrix app.
$ cf start greeting-hystrix
  1. Experiment! Refresh the greeting-hystrix / endpoint several times. Take down the fortune-service app. Scale the greeting-hystrix app. What does the dashboard do?

What Just Happened?

The greeting-hystrix application is publishing metrics via AMQP to RabbitMQ (this can be discovered by looking at VCAP_SERVICES). Those metrics are then consumed and aggregated by Turbine. The Circuit Breaker Dashboard then consumes the Turbine endpoint. All of this detail has been abstracted away by using the PCF Circuit Breaker Dashboard Service.