Introduction

A showcase for a microservice architecture and tools while implementing the board game Codenames: Duet

Initial high level architecture details

Main Components

Brief explanation of the components. A more detail explanation is available at the README in the project module.

All modules will serve their API documentation using RestDocs and make it available at the http://COMPONENT_URL/docs/index.html url.

Player Service

A very minimalist approach to register and get player's details

Game Session Service

TBC

Technology Stack

Area	Library	Link
Programming Language	Java 11	tbc
Cache Layer	tbc	tbc
DB layer	Spring Data mybatis	https://mybatis.org/mybatis-3/
Documentation	REST docs
Dev Tools	lombok
Ops	Spring Actuator	https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-features.html
Distributed Tracing	Sleuth Zipkin
Cloud Messaging	Solace PubSub+ Spring Clound Messaging
Databases	H2 mySQL
Database Schema Management	liquibase
Testing	JUnit AssertJ Mockito REST Assured
Deployment	Docker Kubernetes
Build	Maven

TODO:

• Setup a CI/CD solution with TravisCI
• Host on AWS
• Build the Terraform scripts
• Distribute Tracing with Zipkin or Jaeger
• Build an API Gateway utilizing Spring Cloud
• Make use of fault tolerance library, such as Hystrix for the Game Stats Service
• Use Event Storm for the Game Replay Service
• Use Client-Side load balance using Ribbon

Building and running the application

Pre-requisites

TBC

Building

TBC

Setting environment variables

TBC

Running the application

Running zipkin

1 - Make sure zipkin server is up and running

docker run -d -p 9411:9411 openzipkin/zipkin

Navigate your browser to http://localhost:9411/zipkin/, to access its home page

Stopping the application

TBC

Deploying the application on Kubernetes

TBC

Tips, Tricks and things to remember

Technology Stack - Brief explanation

Spring Boot:

@SpringBootApplication is a convenience annotation that adds all of the following:

• @Configuration: Tags the class as a source of bean definitions for the application context.
• @EnableAutoConfiguration: Tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.
• @EnableWebMvc: Flags the application as a web application and activates key behaviors, such as setting up a DispatcherServlet. Spring Boot adds it automatically when it sees spring-webmvc on the classpath.
• @ComponentScan: Tells Spring to look for other components, configurations, and services in the the com.example.testingrestdocs package, letting it find the HelloController class.

Spring Cloud Sleuth

Spring Cloud Sleuth adds two types of IDs to your logging:

• Trace Id: A unique ID that remains the same throughout the request containing multiple microservices.
• Span Id: A unique ID per microservice.

Basically, a Trace ID will contain multiple Span ID which can easily be used by log aggregation tools.

        <dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-sleuth</artifactId>
		</dependency>

Sleuth Integration with Zipkins

Zipkins is a distributed tracing system usually used to troubleshoot latency problems in service architectures.

We have to tell Sleuth to send data to the Zipkin server by adding a dependency to the pom.xml:

<dependency>  
 <groupId>org.springframework.cloud</groupId>  
 <artifactId>spring-cloud-starter-zipkin</artifactId>  
</dependency>

and adding following properties in the application.yaml

spring
   sleuth
      sampler
         probability: 100  
spring
   zipkin
      baseUrl: http://localhost:9411/

The spring.zipkin.baseUrl property tells Spring and Sleuth where to push data to. Also, by default, Spring Cloud Sleuth sets all spans to non-exportable. This means these traces (Trace Id and Span Id) appear in logs but are not exported to another remote store like Zipkin.

In order to export spans to the Zipkin server, we need to set a sampler rate using spring.sleuth.sampler.probability. A value of 100 means all the spans will be sent to the Zipkin server too.