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Load balancer does not have available server for client

由 亡梦爱人 提交于 2019-12-03 00:22:45

After doing research, and with help of @Bloodysock, I found that I was missing registration of remote server in 'client-app' micro-service. The document is at Spring Cloud Netflix.

I used Ribbon without Eureka with configuration in application.yml in 'client-app' micro-service as:

movie-api:
  ribbon:
    listOfServers: http://localhost:8090
Luciano Nery

The problem is that your service doesn't know the host of requested service. If you are using Eureka, put this line on your .properties or .yml file:

eureka.client.fetchRegistry=true

OR

eureka:
    client:
        fetchRegistry: true

It'll make your service talk with Eureka and discovers host of requested service.

If your Spring Cloud set up does not support specifying the servers in application.properties/application.yml, you have to configure the services URL in a Configuration class.

Pls, note the warning message in my application.properties [Spring Boot v2.0.0RELEASE, spring-cloud-starter-feign & spring-cloud-starter-ribbon v 1.4.3.RELEASE]

So what I did was to write a Configuration class as follows:

@Configuration
class LocalRibbonClientConfiguration {
    @Bean
    public ServerList<Server> ribbonServerList() {
        // return new ConfigurationBasedServerList();
        StaticServerList<Server> staticServerList = new StaticServerList<>((new Server("localhost", 8001)),
                new Server("localhost", 8000));
        return staticServerList;
    }
}

Then, configured the Spring Boot Application to use this configuration as follows:

@SpringBootApplication
@EnableFeignClients("my-package.currencyconversionservice")
@RibbonClient(name = "currency-conversion-service", configuration = LocalRibbonClientConfiguration.class)
public class CurrencyConversionServiceApplication {
 // nothing new here...
}

No need to change the Feign Proxy class. Posting just for this post to be served as a complete solution to the problem:

@FeignClient(name="currency-exchange-service")
@RibbonClient(name="currency-exchange-service")
public interface CurrencyExchangeServiceProxy {
    @GetMapping("/currency-exchange/from/{from}/to/{to}")
    public CurrencyConversionBean retrieveExchangeValue(@PathVariable("from") String from, @PathVariable("to") String to);
}

That's all. The problem was fixed.

I nearly wasted 2 hours to find the root cause. I mistakenly imported EnableEurekaClient in client application, which was the root cause for the issue. I finally resolved this issue by removing the import. To my surprise @EnableDiscoveryClient does not require the below dependency. But if you are using Eureka Naming server than this has to be used. 

   <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        <version>2.0.0.RELEASE</version>
    </dependency>

Make sure your ribbion client is correct.

package com.in28minutes.microservices.currencyconversionservice;

import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;


@FeignClient(name="currency-exchange-service")
@RibbonClient(name="currency-exchange-service") 
public interface CurrencyExchangeServiceProxy {


    @GetMapping("/currency-exchange/from/{from}/to/{to}")
    public CurrencyConversionBean retrieveExchangeValue
        (@PathVariable("from") String from, @PathVariable("to") String to); //mention correct pathvariables
}
标签
Spring
spring-boot
spring-cloud-netflix
netflix-feign
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