Create LoadBalancerClientFilter

pom.xml

@@ -49,6 +49,21 @@
 			<artifactId>spring-boot-configuration-processor</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-starter-ribbon</artifactId>
+			<optional>true</optional>
+			<exclusions>
+				<exclusion>
+					<groupId>com.netflix.ribbon</groupId>
+					<artifactId>ribbon-transport</artifactId>
+				</exclusion>
+				<exclusion>
+					<groupId>io.reactivex</groupId>
+					<artifactId>rxnetty</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-devtools</artifactId>
@@ -75,6 +90,20 @@
 				<type>pom</type>
 				<scope>import</scope>
 			</dependency>
+			<dependency>
+				<groupId>org.springframework.cloud</groupId>
+				<artifactId>spring-cloud-commons-dependencies</artifactId>
+				<version>1.2.0.BUILD-SNAPSHOT</version>
+				<type>pom</type>
+				<scope>import</scope>
+			</dependency>
+			<dependency>
+				<groupId>org.springframework.cloud</groupId>
+				<artifactId>spring-cloud-netflix-dependencies</artifactId>
+				<version>1.3.0.BUILD-SNAPSHOT</version>
+				<type>pom</type>
+				<scope>import</scope>
+			</dependency>
 		</dependencies>
 	</dependencyManagement>
 

src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -4,12 +4,15 @@ import java.util.List;
 import java.util.Map;
 
 import org.springframework.boot.actuate.endpoint.Endpoint;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
 import org.springframework.cloud.gateway.actuate.GatewayEndpoint;
 import org.springframework.cloud.gateway.api.RouteReader;
 import org.springframework.cloud.gateway.filter.GlobalFilter;
+import org.springframework.cloud.gateway.filter.LoadBalancerClientFilter;
 import org.springframework.cloud.gateway.filter.RouteToRequestUrlFilter;
 import org.springframework.cloud.gateway.filter.WriteResponseFilter;
 import org.springframework.cloud.gateway.filter.route.AddRequestHeaderRouteFilter;
@@ -86,6 +89,13 @@ public class GatewayAutoConfiguration {
 
 	// GlobalFilter beans
 
+	@Bean
+	@ConditionalOnClass(LoadBalancerClient.class)
+	@ConditionalOnBean(LoadBalancerClient.class)
+	public LoadBalancerClientFilter loadBalancerClientFilter(LoadBalancerClient client) {
+		return new LoadBalancerClientFilter(client);
+	}
+
 	@Bean
 	public RouteToRequestUrlFilter routeToRequestUrlFilter() {
 		return new RouteToRequestUrlFilter();

src/main/java/org/springframework/cloud/gateway/filter/LoadBalancerClientFilter.java

@@ -0,0 +1,59 @@
+package org.springframework.cloud.gateway.filter;
+
+import java.net.URI;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.cloud.client.ServiceInstance;
+import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
+import org.springframework.core.Ordered;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.server.WebFilterChain;
+import org.springframework.web.util.UriComponentsBuilder;
+
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.getAttribute;
+
+import reactor.core.publisher.Mono;
+
+/**
+ * @author Spencer Gibb
+ */
+public class LoadBalancerClientFilter implements GlobalFilter, Ordered {
+
+	private static final Log log = LogFactory.getLog(LoadBalancerClientFilter.class);
+	public static final int LOAD_BALANCER_CLIENT_FILTER_ORDER = 10100;
+
+	private final LoadBalancerClient loadBalancer;
+
+	public LoadBalancerClientFilter(LoadBalancerClient loadBalancer) {
+		this.loadBalancer = loadBalancer;
+	}
+
+	@Override
+	public int getOrder() {
+		return LOAD_BALANCER_CLIENT_FILTER_ORDER;
+	}
+
+	@Override
+	public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
+		URI url = getAttribute(exchange, GATEWAY_REQUEST_URL_ATTR, URI.class);
+		if (url == null || !url.getScheme().equals("lb")) {
+			return chain.filter(exchange);
+		}
+		log.trace("LoadBalancerClientFilter url before: " + url);
+
+		final ServiceInstance instance = loadBalancer.choose(url.getHost());
+
+		URI requestUrl = UriComponentsBuilder.fromUri(url)
+				.scheme(instance.isSecure()? "https" : "http") //TODO: support websockets
+				.host(instance.getHost())
+				.port(instance.getPort())
+				.build(true)
+				.toUri();
+		log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
+		exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
+		return chain.filter(exchange);
+	}
+
+}

src/main/java/org/springframework/cloud/gateway/filter/RouteToRequestUrlFilter.java

@@ -5,7 +5,6 @@ import java.net.URI;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.cloud.gateway.config.Route;
-import org.springframework.cloud.gateway.support.ServerWebExchangeUtils;
 import org.springframework.core.Ordered;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebFilterChain;

src/test/java/org/springframework/cloud/gateway/test/GatewayIntegrationTests.java

@@ -38,7 +38,8 @@ import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
 @RunWith(SpringRunner.class)
-@SpringBootTest(webEnvironment = RANDOM_PORT)
+@SpringBootTest(webEnvironment = RANDOM_PORT,
+		properties = "spring.cloud.bootstrap.enabled=false")
 @SuppressWarnings("unchecked")
 public class GatewayIntegrationTests {
 
@@ -209,6 +210,29 @@ public class GatewayIntegrationTests {
 		);
 	}
 
+	@Test
+	public void loadBalancerFilterWorks() {
+		Mono<ClientResponse> result = webClient.exchange(
+				GET("http://localhost:" + port + "/get")
+						.header("Host", "www.loadbalancerclient.org")
+						.build()
+		);
+
+		verify( () ->
+				StepVerifier.create(result)
+						.consumeNextWith(
+								response -> {
+									HttpHeaders httpHeaders = response.headers().asHttpHeaders();
+									assertThat(httpHeaders.getFirst(ROUTE_ID_HEADER))
+											.isEqualTo("load_balancer_client_test");
+									HttpStatus statusCode = response.statusCode();
+									assertThat(statusCode).isEqualTo(HttpStatus.OK);
+								})
+						.expectComplete()
+						.verify(Duration.ofMinutes(5))
+		);
+	}
+
 	@Test
 	public void postWorks() {
 		ClientRequest<Mono<String>> request = POST("http://localhost:" + port + "/post")

src/test/java/org/springframework/cloud/gateway/test/GatewayTestApplication.java

@@ -9,6 +9,7 @@ import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 public class GatewayTestApplication {
 
 	public static void main(String[] args) {
+		System.setProperty("spring.cloud.bootstrap.enabled", "false"); //TODO: fix bootstrap
 		SpringApplication.run(GatewayTestApplication.class, args);
 	}
 }

src/test/resources/application.yml

@@ -47,6 +47,12 @@ spring:
         filters:
         - AddResponseHeader=X-Request-Foo, Bar
 
+      # =====================================
+      - id: load_balancer_client_test
+        uri: lb://myservice
+        predicates:
+        - Host=**.loadbalancerclient.org
+
       # =====================================
       - id: redirect_to_test
         uri: http://httpbin.org:80
@@ -129,6 +135,12 @@ spring:
         predicates:
         - name: Url
           value: /**
+
+myservice:
+  ribbon:
+    NIWSServerListClassName: com.netflix.loadbalancer.ConfigurationBasedServerList
+    listOfServers: httpbin.org:80
+
 logging:
   level:
     org.springframework.cloud.gateway: TRACE