Experiments

Try the experiments in the following widget!#

Additional microservice#

Supplement the system with an additional microservice.

• A microservice that is used by a call center agent to create notes for a call can be used as an example. The call center agent should be able to select the customer.

• You can copy and modify one of the existing microservices. microservices.

• Register the microservice in Eureka.

• The customer microservice must be called via Ribbon. The microservice will be found automatically via Eureka, otherwise, the microservice must be looked up explicitly in Eureka.

• Package the microservice in a Docker image and add the image to docker-compose.yml. There you can also determine the name of the Docker container.

• Create a link in docker-compose.yml from the container with the new service to the container eureka. That way the microservice can register at the Eureka server.

• The microservice must be accessible from the homepage. To do this, you have to create a link similar to the other links in the file index.html in the Zuul project. Zuul automatically sets up the routing for the microservice as soon as the microservice is registered in Eureka.

Scaling and load balancing#

Try scaling and load balancing.

• Increase the number of instances of a service with docker-compose up --scale customer=2.

• Use the Eureka dashboard to determine whether two customer microservices are running. It is available at port 8761, at http://localhost:8761/ when Docker is running on the local computer.

• Observe the logs of the order microservice with docker logs -f ms_order_1 and have a look at whether different instances of the customer microservice are called. This should be the case because Ribbon is used for load balancing. For this, you have to trigger requests to the order application, e.g., a simple reload of the starting page.

Simulate failure#

Simulate the failure of a microservice.

• Watch the logs of the order microservice with docker logs -f ms_order_1and have a look at how the catalog microservice is called. For this, you have to trigger requests to the order application. For example, you can reload the starting page.

• Find the IP address of the order microservice with the help of the Eureka dashboard at port 8761, http://localhost:8761/ when Docker is running locally.

• Open the Hystrix dashboard at port 8989 on the Docker host, at http://localhost:8989/ when Docker is running on the local computer.

• Using this IP address enter the URL of the Hystrix JSON data stream in the Hystrix dashboard. This can be http://172.18.0.6:8080/actuator/hystrix.stream. The Hystrix dashboard should show closed circuit breakers.

• Shut down all catalog instances with docker-compose up --scale catalog=0.

• Watch the log of the order microservices during the next calls.

• Also observe the Hystrix dashboard. The circuit breaker will only open when multiple calls have failed.

• When the circuit breaker is open, the order microservice should work again since the fallback is activated, then a cached value is used.

Extend access using Hystrix#

Only access to the catalog microservice is safeguarded with Hystrix.

In the order microservice the class CustomerClient in package com.ewolff.microservice.order.clients implements the access to the customer microservice.

Extend the access to the customer microservice using Hystrix. For this, use the class CatalogClient from the same package as an example.

Extend Zuul setup#

Extend the Zuul setup by a fixed route. In application.yml, in directory src/main/resource, in project microservice-demo-zuul-server add for example the following to make the INNOQ homepage appear at http://localhost:8080/innoq:

zuul:
  routes:
    innoq:
      path: /innoq/**
      url: http://innoq.com/

Filter with Zuul#

Add a filter to the Zuul configuration.

A tutorial dealing with Zuul filters can be found at https://spring.io/guides/gs/routing-and-filtering/.

Create your own microservice#

• Create your own microservice that only returns simple HTML.

• Integrate it into Eureka and deploy it as part of the Docker compose environment.

• If it is registered in Eureka, it can be addressed immediately from the Zuul proxy at a URL like http://localhost:8080/mymicroservice .

We’ll conclude this chapter with the next lesson.