Microservices - Part 8 | Building a Microservice using Spring Cloud Config Server + Spring Cloud Bus + Feign Rest Client + Ribbon + Zuul + Spring Cloud Sleuth and Zipkin + Eureka + Hysterix

Ports

Application	Port
Limits Service	8080, 8081, ...
Spring Cloud Config Server	8888
Currency Exchange Service	8000, 8001, 8002, ..
Currency Conversion Service	8100, 8101, 8102, ...
Netflix Eureka Naming Server	8761
Netflix Zuul API Gateway Server	8765
Zipkin Distributed Tracing Server	9411

URLs

Application	URL
Limits Service	http://localhost:8080/limits POST -> http://localhost:8080/actuator/refresh
Spring Cloud Config Server	http://localhost:8888/limits-service/default http://localhost:8888/limits-service/dev
Currency Converter Service - Direct Call	http://localhost:8100/currency-converter/from/USD/to/INR/quantity/10
Currency Converter Service - Feign	http://localhost:8100/currency-converter-feign/from/EUR/to/INR/quantity/10000
Currency Exchange Service	http://localhost:8000/currency-exchange/from/EUR/to/INR http://localhost:8001/currency-exchange/from/USD/to/INR
Eureka	http://localhost:8761/
Zuul - Currency Exchange & Exchange Services	http://localhost:8765/currency-exchange-service/currency-exchange/from/EUR/to/INR  http://localhost:8765/currency-conversion-service/ currency-converter-feign/from/USD/to/INR/quantity/10
Zipkin	http://localhost:9411/zipkin/
Spring Cloud Bus Refresh	http://localhost:8080/bus/refresh

Git :

/03.microservices/git-localconfig-repo/limits-service.properties

limits-service.minimum=8

limits-service.maximum=888

management.endpoints.web.exposure.include=*

Steps to Create a Microservice :

Step 1 : Create a Centralized Microservice Configuration with Spring Cloud Config Server

Dependency : spring-cloud-config-server

Annotation : @EnableConfigServer

application.properties :

spring.application.name=spring-cloud-config-server

server.port=8888

spring.cloud.config.server.git.uri=file:///in28Minutes/git/spring-micro-services/03.microservices/git-localconfig-repo

For Fetching data from this config server add the following in bootstrap.properties for the respective service :
spring.application.name=limits-service
spring.cloud.config.uri=http://localhost:8888
spring.profiles.active=qa
management.endpoints.web.exposure.include=*

Step 2 : Using Spring Cloud Bus to exchange messages about Configuration updates

Implementing a refresh URL to dynamically load properties without restarting respective services.

Dependency : spring-cloud-starter-bus-amqp (to be included in all projects which needs to be interconnected.)

URL :  http://localhost:8080/bus/refresh

Refresh one url, rest all will receive refresh message from rabbitmq or Spring Cloud bus.

Step 3 : Implementing Eureka Server

Dependency : spring-cloud-starter-netflix-eureka-server

Annotation : @EnableEurekaServer

application.properties :

spring.application.name=netflix-eureka-naming-server

server.port=8761

eureka.client.register-with-eureka=false

eureka.client.fetch-registry=false

Step 4: Implementing API Gateway with Zuul

Dependency : spring-cloud-starter-netflix-zuul

Annotation : 

@EnableZuulProxy

@EnableDiscoveryClient

application.properties :

spring.application.name=netflix-zuul-api-gateway-server

server.port=8765

eureka.client.service-url.default-zone=http://localhost:8761/eureka

Step 5 : Implementing Services : Conversion Service -> Exchange Service

Annotation: @EnableDiscoveryClient , @EnableFeignClients("com.in28minutes.microservices.currencyconversionservice")

PS: Create a proxy for calling exchange service from conversion service with automatic detection :
@FeignClient(name="netflix-zuul-api-gateway-server")
@RibbonClient(name="currency-exchange-service")

Step 6 : Enable Distributed Tracing via Zipking and Sleuth

Add Following Bean in gateway + all services :

@Bean

public Sampler defaultSampler(){

return Sampler.ALWAYS_SAMPLE;

}

Plus the following dependency :
                <dependency>

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-starter-sleuth</artifactId>

</dependency>

<dependency>

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-sleuth-zipkin</artifactId>

</dependency>

<dependency>

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-starter-bus-amqp</artifactId>

</dependency>

Step 6.1 : Install rabbit mq and zipkin server.

Step 6.2 : Start a zipkin server :

Annotation : @EnableZipkinServer

dependency : 

                <dependency>

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-sleuth-zipkin-stream</artifactId>

</dependency>

<dependency>

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-starter-stream-rabbit</artifactId>

</dependency>

<dependency>

<groupId>io.zipkin.java</groupId>

<artifactId>zipkin-autoconfigure-ui</artifactId>

<scope>runtime</scope>

</dependency>

 application.properties :

spring.application.name=zipkin-distributed-tracing-server

server.port=9411

Step 7: Implementing Fault Tolerance with Hysterix
Annotation : @EnableHystrix
@HystrixCommand(fallbackMethod="fallbackRetrieveConfiguration")
dependency :
                 <dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>

Ref : https://github.com/in28minutes/spring-microservices/tree/master/03.microservices