Add configuration for clusters endpoint. Closes #2929. (#2966)

docs/src/main/asciidoc/spring-cloud-netflix.adoc

@@ -680,6 +680,29 @@ Spring Cloud provides a `spring-cloud-starter-netflix-turbine` that has all the
 NOTE: By default, Spring Cloud lets Turbine use the host and port to allow multiple processes per host, per cluster.
 If you want the native Netflix behavior built into Turbine to _not_ allow multiple processes per host, per cluster (the key to the instance ID is the hostname), set `turbine.combineHostPort=false`.
 
+==== Clusters Endpoint
+
+In some situations it might be useful for other applications to know what custers have been configured
+in Turbine.  To support this you can use the `/clusters` endpoint which will return a JSON array of
+all the configured clusters.
+
+.GET /clusters
+[source,json]
+----
+[
+  {
+    "name": "RACES",
+    "link": "http://localhost:8383/turbine.stream?cluster=RACES"
+  },
+  {
+    "name": "WEB",
+    "link": "http://localhost:8383/turbine.stream?cluster=WEB"
+  }
+]
+----
+
+This endpoint can be disabled by setting `turbine.endpoints.clusters.enabled` to `false`.
+
 === Turbine Stream
 
 In some environments (such as in a PaaS setting), the classic Turbine model of pulling metrics from all the distributed Hystrix commands does not work.

spring-cloud-netflix-turbine/src/main/java/org/springframework/cloud/netflix/turbine/ClusterInformation.java

@@ -4,8 +4,10 @@ import java.util.Objects;
 
 public class ClusterInformation {
 
-    private final String name;
-    private final String link;
+    private String name;
+    private String link;
+
+    public ClusterInformation(){};
 
     public ClusterInformation(String name, String link) {
         this.name = name;
@@ -20,6 +22,14 @@ public class ClusterInformation {
         return link;
     }
 
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public void setLink(String link) {
+		this.link = link;
+	}
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;

spring-cloud-netflix-turbine/src/main/java/org/springframework/cloud/netflix/turbine/TurbineHttpConfiguration.java

@@ -20,6 +20,7 @@ import com.netflix.turbine.monitor.cluster.ClusterMonitorFactory;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
 import org.springframework.cloud.client.actuator.HasFeatures;
@@ -55,6 +56,18 @@ public class TurbineHttpConfiguration {
 		return new TurbineProperties();
 	}
 
+	@Bean
+	@ConditionalOnMissingBean
+	public TurbineInformationService turbineInformationService() {
+		return new TurbineInformationService();
+	}
+
+	@Bean
+	@ConditionalOnProperty(value = "turbine.endpoints.clusters.enabled", matchIfMissing = true)
+	public TurbineController turbineController(TurbineInformationService service) {
+		return new TurbineController(service);
+	}
+
 	@Bean
 	@ConditionalOnMissingBean
 	public TurbineAggregatorProperties turbineAggregatorProperties() {

spring-cloud-netflix-turbine/src/test/java/org/springframework/cloud/netflix/turbine/TurbineHttpTests.java

@@ -16,13 +16,23 @@
 
 package org.springframework.cloud.netflix.turbine;
 
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import javax.servlet.http.HttpServletRequest;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
+import static org.junit.Assert.assertEquals;
+
 /**
  * @author Spencer Gibb
  */
@@ -30,12 +40,38 @@ import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 @SpringBootTest(classes = TurbineHttpTests.TurbineHttpSampleApplication.class, webEnvironment = WebEnvironment.RANDOM_PORT)
 public class TurbineHttpTests {
 
+	private static final ClusterInformation foo = new ClusterInformation("foo", "http://foo");
+	private static final ClusterInformation bar = new ClusterInformation("bar", "http://bar");
+
+	@Autowired
+	TestRestTemplate rest;
+
 	@EnableAutoConfiguration
 	@EnableTurbine
 	public static class TurbineHttpSampleApplication {
+
+		@Configuration
+		static class MyConfig {
+			@Bean
+			TurbineInformationService myInfoService() {
+				return new TurbineInformationService() {
+					@Override
+					public Collection<ClusterInformation> getClusterInformations(HttpServletRequest request) {
+						List<ClusterInformation> clusterInformationList = new ArrayList<ClusterInformation>();
+						clusterInformationList.add(foo);
+						clusterInformationList.add(bar);
+						return clusterInformationList;
+					}
+				};
+			}
+		}
 	}
 
 	@Test
 	public void contextLoads() {
+		ClusterInformation[] clusters = rest.getForObject("/clusters", ClusterInformation[].class);
+		assertEquals(2, clusters.length);
+		assertEquals(foo, clusters[0]);
+		assertEquals(bar, clusters[1]);
 	}
 }