Boost Spring Boot Microservices with Reactive Feign: A Complete Guide

Environment: SpringBoot 2.7.15 + feign-reactor-cloud 3.3.0

Introduction

OpenFeign is part of Spring Cloud, providing declarative service calls and load balancing. Its main features include support for Spring MVC annotations, built‑in load balancing, declarative remote calls, pluggable annotations, asynchronous communication, circuit‑breaker integration (e.g., resilience4j), and service discovery with Nacos or a load‑balancer.

However, OpenFeign does not support reactive clients such as Spring WebClient, and Spring Cloud OpenFeign also lacks this capability.

feign‑reactor extends Spring Cloud Feign with Reactor Netty support, enabling a reactive programming model, better asynchronous request handling, and additional features like load balancing, circuit‑breaker, and custom request/response handling.

Using feign‑reactor is essentially the same as OpenFeign, only the annotation names differ.

Environment Setup

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

<dependency>
  <groupId>com.playtika.reactivefeign</groupId>
  <artifactId>feign-reactor-spring-configuration</artifactId>
  <version>3.3.0</version>
</dependency>

<dependency>
  <groupId>com.playtika.reactivefeign</groupId>
  <artifactId>feign-reactor-cloud</artifactId>
  <version>3.3.0</version>
</dependency>

<dependency>
  <groupId>com.playtika.reactivefeign</groupId>
  <artifactId>feign-reactor-webclient</artifactId>
  <version>3.3.0</version>
</dependency>

The feign-reactor-cloud dependency adds circuit‑breaker and load‑balancer support; feign-reactor-webclient provides a WebClient‑based implementation; feign-reactor-spring-configuration supplies Spring auto‑configuration.

Enable Reactive Feign

@SpringBootApplication
@EnableReactiveFeignClients
public class SpringcloudFeignReactorApplication { }

Reactive Feign Interface Definition

@ReactiveFeignClient(
    url = "http://localhost:8088/demos",
    name = "demoReactorFeign",
    fallback = DemoReactorFeignFallback.class,
    configuration = {DemoReactorFeignConfig.class}
)
public interface DemoReactorFeign {
    @GetMapping("/info/{id}")
    Mono<Object> info(@PathVariable("id") Integer id);
}

Fallback Implementation

public class DemoReactorFeignFallback implements DemoReactorFeign {
    @Override
    public Mono<Object> info(Integer id) {
        return Mono.just("Request failed");
    }
}

Configuration Class

public class DemoReactorFeignConfig {
    @Bean
    public DemoReactorFeignFallback demoReactorFeignFallback() {
        return new DemoReactorFeignFallback();
    }
}

Test Controller

@RestController
@RequestMapping("/reactor")
public class DemoController {
    @Resource
    private DemoReactorFeign demoReactorFeign;

    @GetMapping("/{id}")
    public Object info(@PathVariable("id") Integer id) {
        return this.demoReactorFeign.info(id);
    }
}

Timeout Support

Timeouts can be configured globally:

reactive:
  feign:
    client:
      config:
        default:
          options:
            connectTimeoutMillis: 1000
            readTimeoutMillis: 1000

Or per‑client:

reactive:
  feign:
    client:
      config:
        demoReactorFeign:
          options:
            connectTimeoutMillis: 2000
            readTimeoutMillis: 2000

Programming Approach

Feign can also be used programmatically:

public class ProgramReactorFeignMain {
    @Headers({"Accept: application/json"})
    static interface DemoReactorFeign {
        @RequestLine("GET /info/{id}")
        Mono<Object> info(@Param("id") Integer id);
    }

    public static void main(String[] args) throws Exception {
        DemoReactorFeign target = WebReactiveFeign
            .<DemoReactorFeign>builder()
            .target(DemoReactorFeign.class, "http://localhost:8088/demos");
        target.info(6666).doOnNext(System.out::println).block();
    }
}

Done!