Brief introduction
In a distributed system dependencies between services and service complex, an unavoidable situation is that some services will fail, leading to other services that depend on them appear thread blocking remote scheduling. A single point of failure for a service request will cause a user's request is blocked, the end result is a thread of depleted resources of the entire service. Because dependency services, other services that depend on will lead to the failure of the service is also in a thread is blocked state, eventually leading thread depleted resources of these services, until not available, resulting in the entire service system is not available, that the avalanche effect. In order to prevent the avalanche effect, resulting in a fuse model.
SpringCloud Netflix realized the name breaker library called Hystrix, provides a fuse function, can prevent failures in distributed systems linked appears. Hystrix is prevented by isolating service access point linkage failure, and failure to provide a solution that increases the elasticity of the entire distributed system.
When the number of failures of a service API interface is less than the threshold value is set within a certain time, the fuse is in a closed state, the normal service API interface. When the number of failures API interface processing request is set greater than a threshold, it is determined that the API interface MAMMALIA, fails, the fuse opens, when requesting the API interface performs a logical fail-fast (i.e., back to the logical fallback retreat), do not perform business logic, not a request thread is blocked. Fuse in the open state, after a period of time in a semi-open state, and a normal request to perform a certain number of logic to perform fast the remaining requests will fail, if requested to perform normal logic fails, the fuse continues to open, if successful, turn off the fuse. Such fuses have the ability to repair itself.
Figure B service fails for some reason, becomes unavailable, all calls to the service B timeout. B when the call fails to reach a particular threshold value (within 5 seconds occurs 20 times the default value Hystrix failure is defined above), a link will be in the open state, then all calls to the service B will not be execution, replaced by a circuit breaker provided a link open message Fallback representation. Hystrix provides the appropriate mechanism that allows developers to define the Fallbak news.
open link blocked waterfall error, can be submerged or let the wrong time to repair service. This fallback may call another Hystrix protection, static data, or legally null values. Fallbacks can form a chain structure, so the bottom of the first call Fallback other business services to return static data.
Fuses on the Ribbon and RestTemplate
POM.xml add dependencies
<!--ribbon中使用断路器-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
Modify the startup class
Plus @EnableHystrix notes, open hystrix fuse function
- RibbonApplication.java
package org.springcloud.ribbon;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
@SpringBootApplication
@EnableDiscoveryClient
@EnableHystrix
public class RibbonApplication {
public static void main(String[] args) {
SpringApplication.run(RibbonApplication.class, args);
}
}
Modify Service Service
On the hi () method plus @HystrixCommand comment. With this comment hi () method on Hystrix fuse function is enabled, in which:
@HystrixCommand shows that the method is hystrix package, can be isolated reliance on service, demotion, fail fast, fast retry hystrix related functions, etc.
- fallbackMethod downscaling methods
- commandProperties common configuration attribute, the corresponding attribute HystrixCommand may be configured, for example, thread pool or the amount of signal isolation, rules, etc. blown fuse
- ignoreExceptions ignore the exception, not included in the default HystrixBadRequestException fail
- groupKey () group name, default class name
- commandKey command name, use the default name
fallbackMethod is rolled back (fallback) logic methods. In the present example, a direct return string. In the open state of the fuse, the logic performs fallback. The best fallback logic is to return some static string, it does not require complex logic, not remotely invoke other services, so easy to perform a quick failure, release thread resources. If you must invoke other services in remote fallback logic, the best in the remote call other services, also add a fuse.
- RibbonService.java
package org.springcloud.ribbon;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
@Service
public class RibbonService {
@Autowired
RestTemplate restTemplate;
@HystrixCommand(fallbackMethod = "hiError")
public String hi(String name){
return restTemplate.getForObject("http://springcloud-eureka-provider/hi?name="+name,String.class);
}
public String hiError(String name){
return "hi,"+name+", use Ribbon + hystrix, eureka-provider is down!";
}
}
In order to start the project
springcloud-Eureka-Cluster-peer1
springcloud-Eureka-Cluster-peer2
springcloud-Eureka-Cluster-peer3
springcloud-eureka-provider1
springcloud-Eureka-Provider2 are
springcloud-Eureka-provider3
springcloud-Ribbon
after all normal start, stop springcloud-eureka-provider1 providers, port: 8001 service
access to the command window curl http://eureka-ribbon.com:8100/hi?name=zhaojq, the circuit breaker is already in force, prompt: service provider hung up
Feign in use in circuit breakers
Modify application.yml file
Feign are self-breaker, it is not turned on by default. You need to open it in the configuration file.
- application.yml
spring:
application:
name: springcloud-feign
freemarker:
prefer-file-system-access: false
security:
user:
name: admin
password: 123456
server:
port: 8101
eureka:
instance:
hostname: eureka-feign.com
instance-id: eureka-feign
client:
service-url:
defaultZone: http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer1.com:8897/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer2.com:8898/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer3.com:8899/eureka/
feign:
hystrix:
enabled: true
Modify FeignConsumer
In @FeignClient annotations fallback class configuration with fail-fast processing. The treatment class as class Feign fuse logic must implement an interface to be modified @FeignClient.
- FeignConsumer.java
package org.springcloud.feign;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
@Component
/*指定这个接口所要调用的提供者服务名称 */
@FeignClient(value = "springcloud-eureka-provider",configuration = FeignConfig.class,fallback = FeignHystrix.class)
public interface FeignConsumer {
@GetMapping(value = "/hi")
String sayHiFromEurekaProvider(@RequestParam(value = "name")String name);
}
New class logic fuse Feign
- FeignHystrix.java
package org.springcloud.feign;
import org.springframework.stereotype.Component;
@Component
public class FeignHystrix implements FeignConsumer {
@Override
public String sayHiFromEurekaProvider(String name) {
eturn "hi,"+name+", use Feign + hystrix, eureka-provider is down!";
}
}
In order to start the project
springcloud-Eureka-Cluster-peer1
springcloud-Eureka-Cluster-peer2
springcloud-Eureka-Cluster-peer3
springcloud-eureka-provider1
springcloud-Eureka-Provider2 are
springcloud-Eureka-provider3
springcloud-Feign
after all normal start, stop springcloud-eureka-provider1 providers, port: 8001 service
access to the command window curl http://eureka-feign.com:8101/hi, the circuit breaker is already in force, prompt: service provider hung up
Hystrix Dashboard
Hystrix Dashboard as a circuit breaker status of a component that provides data monitoring and friendly graphical interface.
Use Hystrix Dashboard in the Ribbon
POM.xml add dependencies
<!--ribbon中使用断路器-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
</dependency>
Modify application.yml file
Start actuator monitoring
- application.yml
spring:
application:
name: springcloud-ribbon
freemarker:
prefer-file-system-access: false
security:
user:
name: admin
password: 123456
server:
port: 8100
# 自定义配置负载均衡策略
Load_Balance:
ribbon:
NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule
eureka:
instance:
hostname: eureka-ribbon.com
instance-id: eureka-ribbon
client:
service-url:
defaultZone: http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer1.com:8897/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer2.com:8898/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer3.com:8899/eureka/
#actuator端口
management:
endpoints:
web:
#修改访问路径 2.0之前默认是/, 2.0默认是 /actuator
base-path: "/actuator"
#开放所有页面节点 默认只开启了health、info两个节点
exposure:
include: '*'
server:
port: 9001
servlet:
context-path: /
ssl:
enabled: false
endpoint:
health:
show-details: always
hystrix:
stream:
enabled: true
Modify the startup class
Plus @EnableHystrixDashboard comment.
- RibbonApplication.java
package org.springcloud.ribbon;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
@SpringBootApplication
@EnableDiscoveryClient
@EnableHystrix
@EnableHystrixDashboard
public class RibbonApplication {
public static void main(String[] args) {
SpringApplication.run(RibbonApplication.class, args);
}
}
In order to start the project
springcloud-eureka-cluster-peer1
springcloud-eureka-cluster-peer2
springcloud-eureka-cluster-peer3
springcloud-eureka-provider1
springcloud-eureka-provider2
springcloud-eureka-provider3
springcloud-ribbon
In the first browser to access the access http://eureka-ribbon.com:8100/hi, then visit http://eureka-ribbon.com:9001/actuator/hystrix.stream, the browser displays the data indicators fuse
Access http://eureka-ribbon.com:8100/hystrix
Click Moniter Stream
This page shows the index data valley fuse, meaning that data indicators as shown in the diagram from Hystrix official document, the document address: https: //github.com/Netflix/Hystrix/wiki
Hystrix Dashboard in use in Feign
POM.xml add dependencies
Feign comes Hystrix dependent not start dependent, so it needs to start adding dependency in the POM
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
</dependency>
Modify application.yml file
Start actuator monitoring
- application.yml
spring:
application:
name: springcloud-feign
freemarker:
prefer-file-system-access: false
security:
user:
name: admin
password: 123456
server:
port: 8101
eureka:
instance:
hostname: eureka-feign.com
instance-id: eureka-feign
client:
service-url:
defaultZone: http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer1.com:8897/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer2.com:8898/eureka/,http://${spring.security.user.name}:${spring.security.user.password}@eureka-peer3.com:8899/eureka/
feign:
hystrix:
enabled: true
management:
endpoints:
web:
base-path: "/actuator"
exposure:
include: "*"
server:
port: 9002
servlet:
context-path: /
ssl:
enabled: false
endpoint:
health:
show-details: always
hystrix:
stream:
enabled: true
Modify the startup class
Plus @EnableHystrix and @EnableHystrixDashboard comment.
- FeignApplication.java
package org.springcloud.feign;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
@EnableHystrix
@EnableHystrixDashboard
public class FeignApplication {
public static void main(String[] args) {
SpringApplication.run(FeignApplication.class, args);
}
}
In order to start the project
springcloud-eureka-cluster-peer1
springcloud-eureka-cluster-peer2
springcloud-eureka-cluster-peer3
springcloud-eureka-provider1
springcloud-eureka-provider2
springcloud-eureka-provider3
springcloud-feign
In the first browser to access the access http://eureka-feign.com:8101/hi, then visit http://eureka-feign.com:9002/actuator/hystrix.stream, the browser displays the data indicators fuse
Access http://eureka-feign.com:8101/hystrix
Click Moniter Stream
