Fault tolerant processing with hystrix

Create a new Maven project hystrix-feign-demo, increase Hystrix Dependence , The code is as follows .

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

Add on the startup class @EnableHystrix perhaps @EnableCircuitBreaker. Be careful ,@EnableHystrix It contains @EnableCircuitBreaker.

Then write a method to call the interface , Add one to it @HystrixCommand annotation , Used to specify the method to be called when a dependent service call is delayed or fails , The code is as follows .

@GetMapping("/callHello")
@HystrixCommand(fallbackMethod = "defaultCallHello")
public String callHello() {
    String result = restTemplate.getForObject("http://localhost:8088/house/hello", String.class);
    return result;
}

It will be used when the call fails to trigger the fusing defaultCallHello Method to go back to the specific content , Definition default-CallHello The code for the method is as follows .

public String defaultCallHello() {
    return "fail";
}

As long as it doesn't start 8088 The service where the port is located , call /callHello Interface , You can see that the returned content is “fail”, Pictured 1 Shown .

Will start... On the class @EnableHystrix Get rid of , Restart the service , Call again /callHello The interface can see that it returns 500 error message , At this time, the fallback function is not used .

{
  code: 500,
  message: "I/O error on GET request for
    "http://localhost:8088/house/hello": Connection refused; nested
      exception is java.net.ConnectException: Connection refused
        ", data:
        null
}

Configuration details
HystrixCommand In addition to fallbackMethod There are many more configurations , Now let's take a look at these configurations , As shown in the following table ：

HystrixCommand Configuration details

Please refer to the official configuration information document ：https://github.com/Netflix/Hystrix/wiki/Configuration.

It's all listed above Hystrix Configuration information , So in Spring Cloud How to use it in English ？ Just use it on the interface method HystrixCommand annotation （ As shown in the following code ）, Just specify the corresponding attribute .

@HystrixCommand(fallbackMethod = "defaultCallHello",commandProperties = {
        @HystrixProperty(name="execution.isolation.strategy", value = "THREAD")
    }
)
@GetMapping("/callHello")
public String callHello() {
    String result = restTemplate.getForObject("http://localhost:8088/house/hello", String.class);
    return result;
}