UnknowhHostException using spring-cloud-starter-gateway with spring boot 2.4.0 and above

user_1384536 0
Viewed 1824

Related to https://github.com/reactor/reactor-netty/issues/1431.

Spring cloud gateway server starts correctly but requests via the gateway fail with the below exception:

java.net.UnknownHostException: failed to resolve 'myserver' after 4 queries
at io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:1013)
Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
Error has been observed at the following site(s):
|_ checkpoint ? org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter [DefaultWebFilterChain]
|_ checkpoint ? org.springframework.cloud.sleuth.instrument.web.TraceWebFilter [DefaultWebFilterChain]
|_ checkpoint ? org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
|_ checkpoint ? HTTP GET "/service/api/applications/123" [ExceptionHandlingWebHandler]
Stack trace:
at io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:1013)
at io.netty.resolver.dns.DnsResolveContext.tryToFinishResolve(DnsResolveContext.java:966)
at io.netty.resolver.dns.DnsResolveContext.query(DnsResolveContext.java:414)
at io.netty.resolver.dns.DnsResolveContext.onResponse(DnsResolveContext.java:601)
at io.netty.resolver.dns.DnsResolveContext.access$400(DnsResolveContext.java:63)
at io.netty.resolver.dns.DnsResolveContext$2.operationComplete(DnsResolveContext.java:458)
.....

Works correctly when downgrading spring boot.
spring-cloud-gateway spring-boot dns spring
2 Answers

Fixed by adding the below bean definition:

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import io.netty.resolver.DefaultAddressResolverGroup;
import reactor.netty.http.client.HttpClient;

@Configuration
public class TempFixConfig {

    @Bean
    public HttpClient webClient() {
        return HttpClient.create().resolver(DefaultAddressResolverGroup.INSTANCE);
    }
}
user_13845360

If you don't want to change the logic of how the HttpClient bean is created, you can add a HttpClientCustomizer:

import org.springframework.cloud.gateway.config.HttpClientCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import io.netty.resolver.DefaultAddressResolverGroup;
import reactor.netty.http.client.HttpClient;

@Configuration
public class HttpClientResolverFixConfig {

    @Bean
    public HttpClientCustomizer httpClientResolverCustomizer() {
        return new HttpClientCustomizer() {

            @Override
            public HttpClient customize(HttpClient httpClient) {
                return httpClient.resolver(DefaultAddressResolverGroup.INSTANCE);
            }
        };
    }

}
user_46823590
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