Configuring Auto Retry for Spring Boot-Netflix Zuul API Gateway

https://github.com/buddhiprab/zuul-gateway-retry

When Netflix Zuul is used as a gateway to forward the incoming requests to backend services, there is always a chance that a request may fail to back end service.

When a request fails, you may want to have the request be retried automatically. To do so when using Sping Cloud Netflix, you need to include Spring Retry on your application’s classpath. When Spring Retry is present, load-balanced Zuul automatically retry any failed requests (as below example configurations Zuul will retry 2 times if a backend service is down).

Application Architecture with Spring Cloud Netflix components

Zuul auto retry scenario

- The default HTTP client used by Zuul is now backed by the Apache HTTP Client instead of the deprecated Ribbon RestClient.

- Netflix Ribbon HTTP client: Enabled by setting ribbon.restclient.enabled=true. This client has limitations, including that it does not support the PATCH method, but it also has built-in retry.

Zuul Gateway Application

<spring-cloud.version>Hoxton.SR4</spring-cloud.version>

application.yml

note that for the gateway, urls are prefixed by /api

Zuul, uses An Apache HTTP client which leverages Spring Retry to retry failed requests.
two classes to explore
public class RetryableRibbonLoadBalancingHttpClient
      extends RibbonLoadBalancingHttpClient
public class RibbonLoadBalancedRetryPolicy implements LoadBalancedRetryPolicy 

you can control the retry functionality by configuring certain Ribbon properties. To do so, set the ribbon.MaxAutoRetries, ribbon.MaxAutoRetriesNextServer, and ribbon.OkToRetryOnAllOperations properties.

server:
  port: 8080

spring:
  application:
    name: gateway
  cloud:
    loadbalancer:
      retry:
        enabled: true

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8085/eureka/
    fetch-registry: true
    register-with-eureka: true
  instance:
    prefer-ip-address: true
    lease-renewal-interval-in-seconds: 5

zuul:
  prefix: /api
  retryable: true

ribbon:
  OkToRetryOnAllOperations: true
  MaxAutoRetries: 2

pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.3.0.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.api</groupId>
   <artifactId>gateway</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>gateway</name>
   <description>API Gateway project for Spring Boot</description>

   <properties>
      <java.version>11</java.version>
      <spring-cloud.version>Hoxton.SR4</spring-cloud.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-jpa</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.retry</groupId>
         <artifactId>spring-retry</artifactId>
         <version>1.3.0</version>
      </dependency>

      <dependency>
         <groupId>com.h2database</groupId>
         <artifactId>h2</artifactId>
         <scope>runtime</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>

GatewayApplication.java

package com.api.gateway;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

@SpringBootApplication
@EnableZuulProxy
@EnableDiscoveryClient
public class GatewayApplication {

   public static void main(String[] args) {
      SpringApplication.run(GatewayApplication.class, args);
   }

}

Discovery Server

application.yml

server:
  port: 8085

spring:
  application:
    name: eureka
  boot:
    admin:
      context-path: /admin

eureka:
  instance:
    hostname: localhost
    lease-renewal-interval-in-seconds: 5
  client:
    registerWithEureka: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
    registry-fetch-interval-seconds: 5

pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.3.0.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.api</groupId>
   <artifactId>eureka</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>eureka</name>
   <description>Demo project for Spring Boot</description>

   <properties>
      <java.version>11</java.version>
      <spring-cloud.version>Hoxton.SR5</spring-cloud.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
      </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>

EurekaApplication.java

package com.api.eureka;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class EurekaApplication {

   public static void main(String[] args) {
      SpringApplication.run(EurekaApplication.class, args);
   }

}

Service 1

application.yml

server:
  port: 8090

spring:
  application:
    name: service1

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8085/eureka/
  instance:
    preferIpAddress: true

pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.3.0.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.api</groupId>
   <artifactId>service1</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>service1</name>
   <description>Demo project for Spring Boot</description>

   <properties>
      <java.version>11</java.version>
      <spring-cloud.version>Hoxton.SR5</spring-cloud.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
      </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>

Service1Application.java

package com.api.service1;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class Service1Application {

   public static void main(String[] args) {
      SpringApplication.run(Service1Application.class, args);
   }

}

ServiceController.java

package com.api.service1.controllers;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/*created by Buddhi*/

@RestController
public class ServiceController {

    @GetMapping("/test1")
    public ResponseEntity test(@RequestParam(name = "param1") String param1) {
        return new ResponseEntity("/service1/test1?param1="+param1, HttpStatus.OK);
    }

}

service 2, service 3 please refer git repo