Spring Cloud : Zuul throwing "Load balancer does not have available server for client"

Question

I am trying to get a simple microservice to register to the Eureka Server and then have Zuul proxy to the microservice. I got the microservice to register to the Eureka Server. However, whenever I bring the Zuul service up I see that it is not registering to the Eureka Server. Whenever I try to route to the microservice I get the below exception:

Load balancer does not have available server for client: microservice

I am not able to figure out where the issue is. Any help would be greatly appreciated

Below are my Spring Boot classes for each of these components.

Microservice Components

MicroserviceApplication.java

@SpringBootApplication(scanBasePackages = { "some.package.controller", "some.package.service" })
@EnableEurekaClient
@EnableJpaRepositories("some.package.repository")
@EntityScan("some.package.entity")
public class MicroserviceApplication {

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

}

bootstrap.yml

server:
  port: 8090

info:
  component: Core Services

spring:
  application:
    name: microservice

application.yml

eureka:
  instance:
    leaseRenewalIntervalInSeconds: 1
    leaseExpirationDurationInSeconds: 2
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
    healthcheck:
      enabled: true
    lease:
      duration: 5

#some other logging and jpa properties below

Eureka Server Components

EurekaServerApplication.java

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

}

bootstrap.yml

spring:
  application:
    name: discovery-server

application.yml

server:
  port: 8761

info:
  component: Discovery Server

eureka:
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
  instance:
    hostname: localhost
  server:
    waitTimeInMsWhenSyncEmpty: 0

API Gateway Components

ZuulGatewayApplication.java

@SpringBootApplication
@EnableZuulProxy
public class ZuulGatewayApplication {
    public static void main(String[] args) {
        SpringApplication.run(ZuulGatewayApplication.class, args);
    }

    @Bean
    public ZuulGatewayPreFilter gatewayPreFilter() {
        return new ZuulGatewayPreFilter();
    }
}

bootstrap.yml

spring:
  application:
    name: api-gateway

application.yml

server:
  port: 8888

info:
  component: API Gateway

eureka:
  instance:
    leaseRenewalIntervalInSeconds: 1
    leaseExpirationDurationInSeconds: 2
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

zuul:
  routes:
    microservice: 
      path: /microservice/**
      serviceId: microservice

Answer 1

Adding @EnableEurekaClient solved this issue. The Zuul application is now discoverable in the Eureka server and is able to route requests.

Answer 2

I had the correct annotation on my Zuul application @EnableZuulClient but still got that error.

The problem was that I started all the applications (Eureka, Zuul and the third application) at the same time instead of doing this one by one. So they all needed time to register. After some time, the error was gone and I could reach my service through Zuul client.