Feign remote call

1、 brief introduction

Feign yes Netflix Developed ⼀ It's a lightweight RESTful Of HTTP Service client （⽤ It makes requests , Remote dispatching ⽤ Of ）, In order to Java Pick up ⼝ Annotated ⽅ It's the tone ⽤Http request ,⽽ No ⽤ image Java Through encapsulation HTTP Ask for the newspaper ⽂ Of ⽅ Direct adjustment ⽤,Feign By ⼴ Pan Ying ⽤ stay Spring Cloud The solution of the ⽅ In the case .

Be similar to Dubbo, The service consumer gets the service provider's answer ⼝, And then it's like ⽤ Local connection ⼝⽅ Law ⼀ sample Detuning ⽤, It's actually a remote request

Feign Can help us more convenient , Elegant tone ⽤HTTP API： We don't need to splice url then Tweed tune ⽤restTemplate Of api, stay SpringCloud in , send ⽤Feign⾮ Often simple , establish ⼀ individual Pick up ⼝（ In consumer -- Service transfer ⽤⽅ this ⼀ End ）, And pick up ⼝ Add ⼀ Some notes , The code is complete 了

SpringCloud Yes Feign Into the ⾏ It enhances , send Feign⽀ Hold on SpringMVC annotation （OpenFeign）

The essence ： Encapsulates the Http transfer ⽤ technological process , More in line with ⾯ To connect ⼝ The programming habit of Standardization , Be similar to Dubbo Service for transfer ⽤

2、 To configure

【1】：maven rely on

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

【2】： Start class enable ⽤ annotation @EnableFeignClients add to Feign⽀ a

        

【3】： establish Feign Pick up ⼝

package com.cc.gateway.feign;

import com.cc.common.dto.UserDto;
import com.cc.common.vo.ReturnVo;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * @author cc
 * @data 2021 year 06 month 30 Japan  18:01
 */
// "project-oauth"  The service name 
@FeignClient(name = "project-oauth", fallback = OauthFallback.class)
public interface OauthFeign {

    /**
     * token verification 
     * @author cc
     * @date 2021/6/30 22:59
     * @param dto
     * @return com.cc.common.vo.ReturnVo
     */
    // "/oauth/checkToken"  Call path 
    @RequestMapping("/oauth/checkToken")
    public ReturnVo<Boolean> checkToken(@RequestBody UserDto dto);
}

3、 Load balancing

Feign It's integrated Ribbon Dependence and ⾃ Dynamic configuration , So we don't need to introduce ⼊ rely on , can In order to pass the ribbon.xx Come on in ⾏ Global configuration , You can also use the service name .ribbon.xx To enter... For the specified service ⾏ Detailed configuration

ribbon:
  # Request connection timeout 
  ConnectTimeout: 3000
  # Request processing timeout 
  ReadTimeout: 15000
  # For all operations ⾏ retry 
  OkToRetryOnAllOperations: false
  #### According to the above configuration , When accessing a fault request , It will try again to access ⼀ Second current instance （ The number of times by MaxAutoRetries To configure ）,
  #### If you don't ⾏, Just change it ⼀ This is an example ⾏ visit , If not ⾏, Change again ⼀ Instance access （ The replacement times are determined by MaxAutoRetriesNextServer To configure ）,
  #### If still not ⾏, Return failure information .
  MaxAutoRetries: 0 # Number of retries for the currently selected instance , Excluding the ⼀ Secondary modulation ⽤
  MaxAutoRetriesNextServer: 0 # Number of retries to switch instances 
  NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RoundRobinRule # Load policy adjustment 

4、 Fuse support

【1】： stay Feign client ⼯ Process configuration ⽂ Pieces of （application.yml） In the open Feign For fuses ⽀ a

#  Turn on Feign Fusing function of 
feign:
  hystrix:
  enabled: true

Hystrix timeout

hystrix:
  command:
    default:
      execution:
        isolation:
          thread:
            ##########################################Hystrix It's super time ⻓ Set up 
            timeoutInMilliseconds: 15000

Be careful ：

Turn on Hystrix after ,Feign Medium ⽅ The law will be entered ⾏⼀ A manager ,⼀ Once there is a problem, go into ⼊ Corresponding fallback logic processing

This is for timeout ⼀ spot , There are currently two timeout settings （Feign/hystrix）, When the fuse is blown, it is a root According to the most ⼩ It's worth entering ⾏ Of , That is, when processing ⻓ The time-out exceeds the shortest time ⼊ Fallback demotion logic

⾃ Definition FallBack Processing class

package com.cc.gateway.feign;

import com.cc.common.dto.UserDto;
import com.cc.common.utils.ReturnVoUtil;
import com.cc.common.vo.ReturnVo;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestBody;

/**
 * @author cc
 * @data 2021 year 06 month 30 Japan  18:02
 */
@Component
public class OauthFallback implements OauthFeign {
    @Override
    public ReturnVo<Boolean> checkToken(@RequestBody UserDto dto) {
        return ReturnVoUtil.success(" Please login again ", false);
    }
}

5、Feign For request compression and response compression ⽀ a

Feign ⽀ Keep up with requests and responses ⾏GZIP Compress , To reduce the performance loss in the communication process . Through the next ⾯ Parameters of You can turn on the compression function of request and response ：

feign:
 compression:
  request:
   enabled: true #  Turn on request compression 
   mime-types: text/html,application/xml,application/json #  Set compressed data type , This is also the default 
   min-request-size: 2048 #  Set the ⼤⼩ Lower limit , This is also the default 
  response:
   enabled: true #  Turn on response compression