Hystrix是Netflix的一个库. Hystrix隔离了服务之间的访问点,阻止了它们之间的级联故障,并提供了后备选项.
例如,当您调用3 rd 方时应用程序,发送响应需要更多时间.那么在那个时候,控件转到了回退方法并将自定义响应返回给你的应用程序.
在本章中,您将看到如何在Spring Boot应用程序中实现Hystrix .
首先,我们需要在构建配置文件中添加Spring Cloud Starter Hystrix依赖项.
Maven用户可以添加以下依赖项pom.xml文件 :
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-hystrix</artifactId> </dependency>
Gradle用户可以在build.gradle文件中添加以下依赖项 :
compile('org.springframework.cloud:spring-cloud-starter-hystrix')
现在,将@EnableHystrix注释添加到主要内容中Spring Boot应用程序类文件. @EnableHystrix注释用于将Hystrix功能启用到Spring Boot应用程序中.
主要的Spring Boot应用程序类文件代码在下面和下面给出;
package com.it1352.hystrixapp; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.hystrix.EnableHystrix; @SpringBootApplication @EnableHystrix public class HystrixappApplication { public static void main(String[] args) { SpringApplication.run(HystrixappApplication.class, args); } }
现在编写一个简单的Rest Controller,使其在请求时间3秒后返回String.
@RequestMapping(value = "/") public String hello() throws InterruptedException { Thread.sleep(3000); return "Welcome Hystrix"; }
现在,为Rest API添加@Hystrix命令和@HystrixProperty,并以毫秒为单位定义超时值.
@HystrixCommand(fallbackMethod = "fallback_hello", commandProperties = { @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "1000") })
接下来,如果请求需要很长时间才能响应,请定义回退方法fallback_hello().
private String fallback_hello() { return "Request fails. It takes long time to response"; }
此处显示包含REST API和Hystrix属性的完整Rest Controller类文件 :
@RequestMapping(value = "/") @HystrixCommand(fallbackMethod = "fallback_hello", commandProperties = { @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "1000") }) public String hello() throws InterruptedException { Thread.sleep(3000); return "Welcome Hystrix"; } private String fallback_hello() { return "Request fails. It takes long time to response"; }
在此示例中,REST API编写在主Spring Boot应用程序类文件本身中.
package com.it1352.hystrixapp; import org.springframework.boot.SpringApplication; import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.hystrix.EnableHystrix; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand; @SpringBootApplication @EnableHystrix @RestController public class HystrixappApplication { public static void main(String[] args) { SpringApplication.run(HystrixappApplication.class, args); } @RequestMapping(value = "/") @HystrixCommand(fallbackMethod = "fallback_hello", commandProperties = { @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "1000") }) public String hello() throws InterruptedException { Thread.sleep(3000); return "Welcome Hystrix"; } private String fallback_hello() { return "Request fails. It takes long time to response"; } }
完整的构建配置文件如下:
Maven - pom.xml文件
<?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.it1352</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: 'eclipse' apply plugin: 'org.springframework.boot' group = 'com.it1352' version = '0.0.1-SNAPSHOT' sourceCompatibility = 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}" } }
您可以创建一个可执行的JAR文件,并使用以下Maven或Gradle命令运行Spring Boot应用程序 :
对于Maven,使用命令如图所示 :
mvn clean install
"BUILD SUCCESS"之后",你可以在目标目录下找到JAR文件.
对于Gradle,使用如下所示的命令 :
gradle clean build
在"BUILD SUCCESSFUL"之后,你可以在build/libs目录下找到JAR文件.
现在,使用下面给出的命令运行JAR文件 :
java -jar <JARFILE>
这将在Tomcat端口8080上启动应用程序,如下所示 :
现在,从网络浏览器点击URL http://localhost:8080/,并看到Hystrix的回应. API需要3秒钟才能响应,但Hystrix超时为1秒.