Mastering Spring Cloud

Let me share with you the result of my last couple months of work – the book published on 26th April by Packt. The book Mastering Spring Cloud is strictly linked to the topics frequently published in this blog – it describes how to build microservices using Spring Cloud framework. I tried to create this book in well-known style of writing from this blog, where I focus on giving you the practical samples of working code without unnecessary small-talk and scribbles 🙂 If you like my style of writing, and in addition you are interested in Spring Cloud framework and microservices, this book is just for you 🙂

The book consists of fifteen chapters, where I have guided you from the basic to the most advanced examples illustrating use cases for almost all projects being a part of Spring Cloud. While creating a blog posts I not always have time to go into all the details related to Spring Cloud. I’m trying to describe a lot of different, interesting trends and solutions in the area of Java development. The book describes many details related to the most important projects of Spring Cloud like service discovery, distributed configuration, inter-service communication, security, logging, testing or continuous delivery. It is available on http://www.packtpub.com site: https://www.packtpub.com/application-development/mastering-spring-cloud. The detailed description of all the topics raised in that book is available on that site.

Personally, I particulary recommend to read the following more advanced subjects described in the book:

  • Peer-to-peer replication between multiple instances of Eureka servers, and using zoning mechanism in inter-service communication
  • Automatically reloading configuration after changes with Spring Cloud Config push notifications mechanism based on Spring Cloud Bus
  • Advanced configuration of inter-service communication with Ribbon client-side load balancer and Feign client
  • Enabling SSL secure communication between microservices and basic elements of microservices-based architecture like service discovery or configuration server
  • Building messaging microservices based on publish/subscribe communication model including cunsumer grouping, partitioning and scaling with Spring Cloud Stream and message brokers (Apache Kafka, RabbitMQ)
  • Setting up continuous delivery for Spring Cloud microservices with Jenkins and Docker
  • Using Docker for running Spring Cloud microservices on Kubernetes platform simulated locally by Minikube
  • Deploying Spring Cloud microservices on cloud platforms like Pivotal Web Services (Pivotal Cloud Foundry hosted cloud solution) and Heroku

Those examples and many others are available together with this book. At the end, a short description taken from packtpub.com site:

Developing, deploying, and operating cloud applications should be as easy as local applications. This should be the governing principle behind any cloud platform, library, or tool. Spring Cloud–an open-source library–makes it easy to develop JVM applications for the cloud. In this book, you will be introduced to Spring Cloud and will master its features from the application developer’s point of view.

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Spring Cloud Microservices at Pivotal Platform

Imagine you have multiple microservices running on different machines as multiple instances. It seems natural to think about the tools that helps you in the process of monitoring and managing all of them. If we add that our microservices are created based on the Spring Cloud framework obviously seems we should look at the Pivotal platform. Here is figure with platform’s architecture download from the main Pivotal’s site.

PVDI-Microservices-Architecture

Although Pivotal Platform can run applications written in many languages it has the best support for Spring Cloud Services and Netflix OSS tools like you can see in the figure above. From the possibilities offered by Pivotal we can take advantage of three ways.

Pivotal Cloud Foundry – solution can be ran on public IaaS or private cloud like AWS, Google Cloud Platform, Microsoft Azure, VMware vSphere, OpenStack.

Pivotal Web Services – hosted cloud-native platform available at pivotal.io site.

PCF Dev – the instance which can be run locally as a a single virtual machine. It offers the opportunity to develop apps using an offline environment which basic services installed like Spring Cloud Services (SCS), MySQL, Redis databases and RabbitMQ broker. If you want to run it locally with SCS you need more than 6GB RAM free.

As a Spring Cloud Services there are available Circuit Breaker (Hystrix), Service Registry (Eureka) and standard Spring Configuration Server based on git configuration.

scs

That’s all I wanted to say about the theory. Let’s move on to practice. On the Pivotal website we have detailed materials on how to set it up, create and deploy a simple microservice based on Spring Cloud solutions. In this article I will try to present the essence collected from these descriptions based on one of my standard examples from the previous posts. As always sample source code is available on GitHub. If you are interested in detailed description of the sample application, microservices and Spring Cloud read my previous articles:

Part 1: Creating microservice using Spring Cloud, Eureka and Zuul

Part 3: Creating Microservices: Circuit Breaker, Fallback and Load Balancing with Spring Cloud

If you have a lot of free RAM you can install PCF Dev on your local workstation. You need to have Virtual Box installed. Then download and install Cloud Foundry Command Line Interface (CF CLI) and PCF Dev. All is described here. Finally you can run command below and take a small break for coffee. Virtual machine needs to downloaded and started.

cf dev start -s scs

For those who do not have RAM enough (like me) there is Pivotal Web Services platform. It is available here. Before use it you have to register on Pivotal site. The rest of the article is identical for both options.
In comparison to previous examples of Spring Cloud based microservices, we need to make some changes. There is one additional dependency inside every microservice’s pom.xml.

<properties>
	...
	<spring-cloud-services.version>1.4.1.RELEASE</spring-cloud-services.version>
	<spring-cloud.version>Dalston.RELEASE</spring-cloud.version>
</properties>

<dependencies>
	<dependency>
		<groupId>io.pivotal.spring.cloud</groupId>
		<artifactId>spring-cloud-services-starter-service-registry</artifactId>
	</dependency>
	...
</dependencies>

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-dependencies</artifactId>
			<version>${spring-cloud.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
		<dependency>
			<groupId>io.pivotal.spring.cloud</groupId>
			<artifactId>spring-cloud-services-dependencies</artifactId>
			<version>${spring-cloud-services.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

We also use Maven Cloud Foundry plugin cf-maven-plugin for application deployment on Pivotal platform. Here is sample for account-service. We run two instances of that microservice with max memory 512MB. Our application name is piomin-account-service.

<plugin>
	<groupId>org.cloudfoundry</groupId>
	<artifactId>cf-maven-plugin</artifactId>
	<version>1.1.3</version>
	<configuration>
		<target>http://api.run.pivotal.io</target>
		<org>piotrminkowski</org>
		<space>development</space>
		<appname>piomin-account-service</appname>
		<memory>512</memory>
		<instances>2</instances>
		<server>cloud-foundry-credentials</server>
	</configuration>
</plugin>

Don’t forget to add credentials configuration into Maven settings.xml file.

<server>
	<id>cloud-foundry-credentials</id>
	<username>piotr.minkowski@gmail.com</username>
	<password>***</password>
</server>

Now, when building sample application we to append cf:push command.

mvn clean install cf:push

Here is circuit breaker implementation inside customer-service.

@Service
public class AccountService {

	@Autowired
	private AccountClient client;

	@HystrixCommand(fallbackMethod = "getEmptyList")
	public List<Account> getAccounts(Integer customerId) {
		return client.getAccounts(customerId);
	}

	List<Account> getEmptyList(Integer customerId) {
		return new ArrayList<>();
	}

}

There is randomly generated delay on the account’s service side, so 25% of calls circuit breaker should be activated.

@RequestMapping("/accounts/customer/{customer}")
public List<Account> findByCustomer(@PathVariable("customer") Integer customerId) {
	logger.info(String.format("Account.findByCustomer(%s)", customerId));
	Random r = new Random();
	int rr = r.nextInt(4);
	if (rr == 1) {
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	return accounts.stream().filter(it -> it.getCustomerId().intValue() == customerId.intValue())
		.collect(Collectors.toList());
}

After successfully deploying application using Maven cf:push command we can go to Pivotal Web Services console available at https://console.run.pivotal.io/. Here are our two deployed services: two instances of piomin-account-service and one instance of piomin-customer-service.

pivotal-1

I have also activated Circuit Breaker and Service Registry from Marketplace.

pivotal-2

Every application need to be bound to service. To enable it select service, then expand Bound Apps overlap and select checkbox next to each service name.

pivotal-4

After this step applications needs to be restarted. It also can be be using web dashboard inside each service.

pivotal-5

Finally, all services are registered in Eureka and we can perform some tests using customer endpoint https://piomin-customer-service.cfapps.io/customers/{id}.

pivotal-4

Final words

With Pivotal solution we can easily deploy, scale and monitor our microservices. Deployment and scaling can be done using Maven plugin or via web dashboard. On Pivotal there are also available some services prepared especially for microservices needs like service registry, circuit breaker and configuration server. Pivotal is a competition for such solutions like Kubernetes which based on Docker containerization (more about this tools here). It is especially useful if you are creating a microservices based on Spring Boot and Spring Cloud frameworks.