Add 'hint' parameter to overloaded methods in RibbonLoadBalancerClient (

#3012)

Fixes gh-3009

spring-cloud-netflix-ribbon/src/main/java/org/springframework/cloud/netflix/ribbon/RibbonLoadBalancerClient.java

@@ -73,7 +73,14 @@ public URI reconstructURI(ServiceInstance instance, URI original) {
 
 	@Override
 	public ServiceInstance choose(String serviceId) {
-		Server server = getServer(serviceId);
+	    return choose(serviceId, null);
+	}
+
+	/**
+	 * New: Select a server using a 'key'.
+	 */
+	public ServiceInstance choose(String serviceId, Object hint) {
+		Server server = getServer(getLoadBalancer(serviceId), hint);
 		if (server == null) {
 			return null;
 		}
@@ -83,8 +90,17 @@ public ServiceInstance choose(String serviceId) {
 
 	@Override
 	public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
+	    return execute(serviceId, request, null);
+	}
+
+	/**
+	 * New: Execute a request by selecting server using a 'key'.
+	 * The hint will have to be the last parameter to not mess with the `execute(serviceId, ServiceInstance, request)`
+	 * method. This somewhat breaks the fluent coding style when using a lambda to define the LoadBalancerRequest.
+	 */
+	public <T> T execute(String serviceId, LoadBalancerRequest<T> request, Object hint) throws IOException {
 		ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
-		Server server = getServer(loadBalancer);
+		Server server = getServer(loadBalancer, hint);
 		if (server == null) {
 			throw new IllegalStateException("No instances available for " + serviceId);
 		}
@@ -140,15 +156,23 @@ private boolean isSecure(Server server, String serviceId) {
 		return RibbonUtils.isSecure(config, serverIntrospector, server);
 	}
 
+	/**
+	 * Note: This method could be removed?
+	 */
 	protected Server getServer(String serviceId) {
-		return getServer(getLoadBalancer(serviceId));
+		return getServer(getLoadBalancer(serviceId), null);
 	}
 
 	protected Server getServer(ILoadBalancer loadBalancer) {
+	    return getServer(loadBalancer, null);
+	}
+
+	protected Server getServer(ILoadBalancer loadBalancer, Object hint) {
 		if (loadBalancer == null) {
 			return null;
 		}
-		return loadBalancer.chooseServer("default"); // TODO: better handling of key
+		// Use 'default' on a null hint, or just pass it on?
+		return loadBalancer.chooseServer(hint != null ? hint : "default");
 	}
 
 	protected ILoadBalancer getLoadBalancer(String serviceId) {
@@ -162,7 +186,7 @@ public static class RibbonServer implements ServiceInstance {
 		private Map<String, String> metadata;
 
 		public RibbonServer(String serviceId, Server server) {
-			this(serviceId, server, false, Collections.<String, String> emptyMap());
+			this(serviceId, server, false, Collections.emptyMap());
 		}
 
 		public RibbonServer(String serviceId, Server server, boolean secure,

spring-cloud-netflix-ribbon/src/test/java/org/springframework/cloud/netflix/ribbon/RibbonLoadBalancerClientTests.java

@@ -43,6 +43,7 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.fail;
+import static org.mockito.ArgumentMatchers.same;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Matchers.anyDouble;
 import static org.mockito.Matchers.anyObject;
@@ -205,6 +206,17 @@ public void testChoose() {
 		RibbonLoadBalancerClient client = getRibbonLoadBalancerClient(server);
 		ServiceInstance serviceInstance = client.choose(server.getServiceId());
 		assertServiceInstance(server, serviceInstance);
+		verify(this.loadBalancer).chooseServer(eq("default"));
+	}
+
+	@Test
+	public void testChooseWithHint() {
+		Object hint = new Object();
+		RibbonServer server = getRibbonServer();
+		RibbonLoadBalancerClient client = getRibbonLoadBalancerClient(server);
+		ServiceInstance serviceInstance = client.choose(server.getServiceId(), hint);
+		assertServiceInstance(server, serviceInstance);
+		verify(this.loadBalancer).chooseServer(same(hint));
 	}
 
 	@Test
@@ -228,6 +240,23 @@ public void testExecute() throws IOException {
                     return returnVal;
                 });
 		verifyServerStats();
+		verify(this.loadBalancer).chooseServer(eq("default"));
+		assertEquals("retVal was wrong", returnVal, actualReturn);
+	}
+
+	@Test
+	public void testExecuteWithHint() throws IOException {
+		Object hint = new Object();
+		final RibbonServer server = getRibbonServer();
+		RibbonLoadBalancerClient client = getRibbonLoadBalancerClient(server);
+		final String returnVal = "myval";
+		Object actualReturn = client.execute(server.getServiceId(),
+				(LoadBalancerRequest<Object>) instance -> {
+					assertServiceInstance(server, instance);
+					return returnVal;
+				}, hint);
+		verifyServerStats();
+		verify(this.loadBalancer).chooseServer(same(hint));
 		assertEquals("retVal was wrong", returnVal, actualReturn);
 	}