Add a heartbeat event every 5s by default

Fixes gh-12

spring-cloud-cloudfoundry-discovery/src/main/java/org/springframework/cloud/cloudfoundry/discovery/CloudFoundryDiscoveryClientConfiguration.java

@@ -75,4 +75,9 @@ public class CloudFoundryDiscoveryClientConfiguration {
 		return new CloudFoundryDiscoveryClient(cloudFoundryClient, environment);
 	}
 
+	@Bean
+	public CloudFoundryHeartbeatSender cloudFoundryHeartbeatSender(CloudFoundryDiscoveryClient client) {
+		return new CloudFoundryHeartbeatSender(client);
+	}
+
 }

spring-cloud-cloudfoundry-discovery/src/main/java/org/springframework/cloud/cloudfoundry/discovery/CloudFoundryDiscoveryProperties.java

@@ -56,6 +56,12 @@ public class CloudFoundryDiscoveryProperties {
 	 */
 	private boolean enabled = true;
 
+	/**
+	 * Frequency in milliseconds of poll for heart beat. The client will poll on this
+	 * frequency and broadcast a list of service ids.
+	 */
+	private long heartbeatFrequency = 5000;
+
 	public boolean isEnabled() {
 		return this.enabled;
 	}
@@ -103,4 +109,12 @@ public class CloudFoundryDiscoveryProperties {
 	public void setSpace(String space) {
 		this.space = space;
 	}
+
+	public long getHeartbeatFrequency() {
+		return this.heartbeatFrequency;
+	}
+
+	public void setHeartbeatFrequency(long heartbeatFrequency) {
+		this.heartbeatFrequency = heartbeatFrequency;
+	}
 }

spring-cloud-cloudfoundry-discovery/src/main/java/org/springframework/cloud/cloudfoundry/discovery/CloudFoundryHeartbeatSender.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.cloudfoundry.discovery;
+
+import java.util.List;
+
+import org.springframework.cloud.client.discovery.event.HeartbeatEvent;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.context.ApplicationEventPublisherAware;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+/**
+ * Publishes a {@link HeartbeatEvent} listing the available services as its state
+ * indicator. If consumers detect a change it means there is a change in the catalog.
+ *
+ * @author Dave Syer
+ *
+ */
+@Component
+public class CloudFoundryHeartbeatSender implements ApplicationEventPublisherAware {
+
+	private final CloudFoundryDiscoveryClient client;
+	private ApplicationEventPublisher publisher;
+
+	public CloudFoundryHeartbeatSender(CloudFoundryDiscoveryClient client) {
+		this.client = client;
+	}
+
+	@Scheduled(fixedDelayString = "${spring.cloud.cloudfoundry.discovery.heartbeatFrequency:5000}")
+	public void poll() {
+		if (this.publisher != null) {
+			List<String> services = this.client.getServices();
+			this.publisher.publishEvent(new HeartbeatEvent(this.client, services));
+		}
+	}
+
+	@Override
+	public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
+		this.publisher = publisher;
+	}
+
+}