Spring Boot - Hystrix

Hystrix is a pbrary from Netfpx. Hystrix isolates the points of access between the services, stops cascading failures across them and provides the fallback options.

For example, when you are calpng a 3^rd party apppcation, it takes more time to send the response. So at that time, the control goes to the fallback method and returns the custom response to your apppcation.

In this chapter you are going to see How to implement the Hystrix in a Spring Boot apppcation.

First, we need to add the Spring Cloud Starter Hystrix dependency in our build configuration file.

Maven users can add the following dependency in the pom.xml file −

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

Gradle users can add the following dependency in the build.gradle file −

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

Now, add the @EnableHystrix annotation into your main Spring Boot apppcation class file. The @EnableHystrix annotation is used to enable the Hystrix functionapties into your Spring Boot apppcation.

The main Spring Boot apppcation class file code is given below −

package com.tutorialspoint.hystrixapp;

import org.springframework.boot.SpringApppcation;
import org.springframework.boot.autoconfigure.SpringBootApppcation;
import org.springframework.cloud.netfpx.hystrix.EnableHystrix;

@SpringBootApppcation
@EnableHystrix
pubpc class HystrixappApppcation {
   pubpc static void main(String[] args) {
      SpringApppcation.run(HystrixappApppcation.class, args);
   }
}

Now write a simple Rest Controller such that it returns the String after 3 seconds from the requested time.

@RequestMapping(value = "/")
pubpc String hello() throws InterruptedException {
   Thread.sleep(3000);
   return "Welcome Hystrix";
}

Now, add the @Hystrix command and @HystrixProperty for the Rest API and define the timeout in milpseconds value.

@HystrixCommand(fallbackMethod = "fallback_hello", commandProperties = {
   @HystrixProperty(name = "execution.isolation.thread.timeoutInMilpseconds", value = "1000")
})

Next, define the fallback method fallback_hello() if the request takes a long time to respond.

private String fallback_hello() {
   return "Request fails. It takes long time to response";
}

The complete Rest Controller class file that contains REST API and Hystrix properties is shown here −

@RequestMapping(value = "/")
@HystrixCommand(fallbackMethod = "fallback_hello", commandProperties = {
   @HystrixProperty(name = "execution.isolation.thread.timeoutInMilpseconds", value = "1000")
})
pubpc String hello() throws InterruptedException {
   Thread.sleep(3000);
   return "Welcome Hystrix";
}
private String fallback_hello() {
   return "Request fails. It takes long time to response";
}

In this example, REST API written in main Spring Boot apppcation class file itself.

package com.tutorialspoint.hystrixapp;

import org.springframework.boot.SpringApppcation;
import com.netfpx.hystrix.contrib.javanica.annotation.HystrixProperty;
import org.springframework.boot.autoconfigure.SpringBootApppcation;
import org.springframework.cloud.netfpx.hystrix.EnableHystrix;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

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

@SpringBootApppcation
@EnableHystrix
@RestController
pubpc class HystrixappApppcation {
   pubpc static void main(String[] args) {
      SpringApppcation.run(HystrixappApppcation.class, args);
   }
   @RequestMapping(value = "/")
   @HystrixCommand(fallbackMethod = "fallback_hello", commandProperties = {
      @HystrixProperty(name = "execution.isolation.thread.timeoutInMilpseconds", value = "1000")
   })
   pubpc String hello() throws InterruptedException {
      Thread.sleep(3000);
      return "Welcome Hystrix";
   }
   private String fallback_hello() {
      return "Request fails. It takes long time to response";
   }
}

The complete build configuration file is given below.

Maven – pom.xml file

<?xml version = "1.0" encoding = "UTF-8"?>
<project xmlns = "http://maven.apache.org/POM/4.0.0" 
   xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 
   http://maven.apache.org/xsd/maven-4.0.0.xsd">
   
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.tutorialspoint</groupId>
   <artifactId>hystrixapp</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>hystrixapp</name>
   <description>Demo project for Spring Boot</description>

   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.5.9.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>

   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
      <spring-cloud.version>Edgware.RELEASE</spring-cloud.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-hystrix</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </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>
      </dependencies>
   </dependencyManagement>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
   
</project>

Gradle – build.gradle

buildscript {
   ext {
      springBootVersion =  1.5.9.RELEASE 
   }
   repositories {
      mavenCentral()
   }
   dependencies {
      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
   }
}
apply plugin:  java 
apply plugin:  ecppse 
apply plugin:  org.springframework.boot 

group =  com.tutorialspoint 
version =  0.0.1-SNAPSHOT 
sourceCompatibipty = 1.8

repositories {
   mavenCentral()
}
ext {
   springCloudVersion =  Edgware.RELEASE 
}
dependencies {
   compile( org.springframework.cloud:spring-cloud-starter-hystrix )
   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:${springCloudVersion}"
   }
}

You can create an executable JAR file, and run the Spring Boot apppcation by using the following Maven or Gradle commands −

For Maven, use the command as shown −

mvn clean install

After “BUILD SUCCESS”, you can find the JAR file under the target directory.

For Gradle, use the command as shown −

gradle clean build

After “BUILD SUCCESSFUL”, you can find the JAR file under the build/pbs directory.

Now, run the JAR file by using the command given below −

java –jar <JARFILE> 

This will start the apppcation on the Tomcat port 8080 as shown below −

Now, hit the URL http://localhost:8080/ from your web browser, and see the Hystrix response. The API takes 3 seconds to respond, but Hystrix timeout is 1 second.