Circuit breaker – Hystrix

Hystrix tool is for circuit breaker operations, that is, latency and fault tolerance.Therefore, Hystrix stops cascading failures. Hystrix performs the real-time operations for monitoring the services and property changes, and supports concurrency.

Gradle Dependency.

buildscript {

ext {

springBootVersion = '2.1.6.RELEASE'

}

repositories {

mavenCentral()

}

dependencies {

classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")

}

}

apply plugin: 'java'

apply plugin: 'eclipse'

apply plugin: 'org.springframework.boot'

apply plugin: 'io.spring.dependency-management'

bootJar {

baseName = 'user'

version = '0.0.1-SNAPSHOT'

}

sourceCompatibility = 1.8

targetCompatibility = 1.8

repositories {

mavenCentral()

}

dependencies {

compile('org.springframework.cloud:spring-cloud-starter-netflix-hystrix')

compile('org.springframework.cloud:spring-cloud-starter-netflix-ribbon')

compile('org.springframework.boot:spring-boot-starter-web')

testCompile('org.springframework.boot:spring-boot-starter-test')

}

dependencyManagement {

imports {

mavenBom "org.springframework.cloud:spring-cloud-dependencies:Finchley.SR2"

}

}

eclipse {

classpath {

containers.remove('org.eclipse.jdt.launching.JRE_CONTAINER')

containers 'org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8'

}

}

Main Class:

package com.example.sayhello;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;

import org.springframework.context.annotation.Bean;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.client.RestTemplate;

@SpringBootApplication

@RestController

@EnableCircuitBreaker

public class SayHelloApplication {

@Bean

  RestTemplate restTemplate(){

    return new RestTemplate();

  }

  @Autowired

  RestTemplate restTemplate;

  

  @Autowired

  ProfileService profileService;

@Bean

public ProfileService getBookService() {

return new  ProfileService(restTemplate);

}

private static Logger log = LoggerFactory.getLogger(SayHelloApplication.class);

@RequestMapping("/callService")

  public Object invoke() {

    Object obj = getBookService().readProfileList();

    return obj;

  }

public static void main(String[] args) {

SpringApplication.run(SayHelloApplication.class, args);

}

}

Service Class:

package com.example.sayhello;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;

import org.springframework.stereotype.Service;

import org.springframework.web.client.RestTemplate;

import java.net.URI;

@Service

public class ProfileService {

  private final RestTemplate restTemplate;

  public ProfileService(RestTemplate rest) {

    this.restTemplate = rest;

  }

  @HystrixCommand(fallbackMethod = "adminProfile")

  public String readProfileList() {

    URI uri = URI.create("http://localhost:8180/user/name/sarath");

    return this.restTemplate.getForObject(uri, String.class);

  }

  public String adminProfile() {

  URI uri = URI.create("http://localhost:8080/user/name/Syed");

    return this.restTemplate.getForObject(uri, String.class);

  }

}

From the above class if the localhost:8180 is not accessible then It will access the localhost:8080. 

Thanks God We end up in seeing the alternate when the service is down.