Cache config client health indicator.

So config server isn't bombarded with requests.

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

@@ -1166,6 +1166,10 @@ If you use another form of security you might need to <<custom-rest-template,pro
 `RestTemplate`>> to the `ConfigServicePropertySourceLocator` (e.g. by
 grabbing it in the bootstrap context and injecting one).
 
+==== Health Indicator
+
+The Config Client supplies a Spring Boot Health Indicator that attempts to load configuration from Config Server. The health indicator can be disabled by setting `health.config.enabled=false`. The response is also cached for performance reasons. The default cache time to live is 5 minutes. To change that value set the `health.config.time-to-live` property (in milliseconds).
+
 [[custom-rest-template]]
 ==== Providing A Custom RestTemplate
 

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/ConfigClientAutoConfiguration.java

@@ -53,6 +53,11 @@ public class ConfigClientAutoConfiguration {
 		return client;
 	}
 
+	@Bean
+	public ConfigClientHealthProperties configClientHealthProperties() {
+		return new ConfigClientHealthProperties();
+	}
+
 	@Configuration
 	@ConditionalOnClass(HealthIndicator.class)
 	@ConditionalOnBean(ConfigServicePropertySourceLocator.class)
@@ -61,24 +66,9 @@ public class ConfigClientAutoConfiguration {
 
 		@Bean
 		public ConfigServerHealthIndicator configServerHealthIndicator(
-				ConfigServicePropertySourceLocator locator, Environment environment) {
-			return new ConfigServerHealthIndicator(locator, environment);
-		}
-	}
-
-	@ConfigurationProperties("health.config")
-	public static class Health {
-		/**
-		 * Flag to indicate that the config server health indicator should be installed.
-		 */
-		boolean enabled;
-
-		public boolean isEnabled() {
-			return this.enabled;
-		}
-
-		public void setEnabled(boolean enabled) {
-			this.enabled = enabled;
+				ConfigServicePropertySourceLocator locator,
+				ConfigClientHealthProperties properties, Environment environment) {
+			return new ConfigServerHealthIndicator(locator, environment, properties);
 		}
 	}
 

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/ConfigClientHealthProperties.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2013-2016 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.config.client;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ * @author Spencer Gibb
+ */
+@ConfigurationProperties("health.config")
+public class ConfigClientHealthProperties {
+	/**
+	 * Flag to indicate that the config server health indicator should be installed.
+	 */
+	boolean enabled;
+
+	/**
+	 * Time to live for cached result, in milliseconds. Default 300000 (5 min).
+	 */
+	private long timeToLive = 60 * 5 * 1000;
+
+	public boolean isEnabled() {
+		return this.enabled;
+	}
+
+	public void setEnabled(boolean enabled) {
+		this.enabled = enabled;
+	}
+
+	public long getTimeToLive() {
+		return timeToLive;
+	}
+
+	public void setTimeToLive(long timeToLive) {
+		this.timeToLive = timeToLive;
+	}
+}

spring-cloud-config-client/src/main/java/org/springframework/cloud/config/client/ConfigServerHealthIndicator.java

@@ -16,17 +16,23 @@ import org.springframework.core.env.PropertySource;
 public class ConfigServerHealthIndicator extends AbstractHealthIndicator {
 
 	private ConfigServicePropertySourceLocator locator;
+	private ConfigClientHealthProperties properties;
 	private Environment environment;
 
+	private long lastAccess = 0;
+
+	private PropertySource<?> cached;
+
 	public ConfigServerHealthIndicator(ConfigServicePropertySourceLocator locator,
-			Environment environment) {
+			Environment environment, ConfigClientHealthProperties properties) {
 		this.environment = environment;
 		this.locator = locator;
+		this.properties = properties;
 	}
 
     @Override
     protected void doHealthCheck(Builder builder) throws Exception {
-		PropertySource<?> propertySource = locator.locate(this.environment);
+		PropertySource<?> propertySource = getPropertySource();
 		builder.up();
 		if (propertySource instanceof CompositePropertySource) {
 			List<String> sources = new ArrayList<>();
@@ -40,4 +46,21 @@ public class ConfigServerHealthIndicator extends AbstractHealthIndicator {
 			builder.unknown().withDetail("error", "no property sources located");
 		}
     }
+
+	private PropertySource<?> getPropertySource() {
+		long accessTime = System.currentTimeMillis();
+		if (isCacheStale(accessTime)) {
+			this.lastAccess = accessTime;
+			this.cached = locator.locate(this.environment);
+		}
+		return this.cached;
+	}
+
+	private boolean isCacheStale(long accessTime) {
+		if (this.cached == null) {
+			return true;
+		}
+		return (accessTime - this.lastAccess) >= this.properties.getTimeToLive();
+	}
+
 }

spring-cloud-config-client/src/test/java/org/springframework/cloud/config/client/ConfigServerHealthIndicatorTests.java

@@ -17,11 +17,16 @@
 package org.springframework.cloud.config.client;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 
 import java.util.Collections;
 
 import org.junit.Test;
-import org.mockito.Mockito;
 import org.springframework.boot.actuate.health.Status;
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MapPropertySource;
@@ -34,11 +39,11 @@ import org.springframework.core.env.PropertySource;
  */
 public class ConfigServerHealthIndicatorTests {
 
-	private ConfigServicePropertySourceLocator locator = Mockito
-			.mock(ConfigServicePropertySourceLocator.class);
-	private Environment environment = Mockito.mock(Environment.class);
+	private ConfigServicePropertySourceLocator locator =
+			mock(ConfigServicePropertySourceLocator.class);
+	private Environment environment = mock(Environment.class);
 	private ConfigServerHealthIndicator indicator = new ConfigServerHealthIndicator(
-			locator, environment);
+			locator, environment, new ConfigClientHealthProperties());
 
 	@Test
 	public void testDefaultStatus() {
@@ -48,15 +53,32 @@ public class ConfigServerHealthIndicatorTests {
 
 	@Test
 	public void testExceptionStatus() {
-		Mockito.doThrow(new IllegalStateException()).when(locator).locate(Mockito.any(Environment.class));
+		doThrow(new IllegalStateException()).when(locator).locate(any(Environment.class));
 		assertEquals(Status.DOWN, indicator.health().getStatus());
+		verify(locator, times(1)).locate(any(Environment.class));
 	}
 
 	@Test
 	public void testServerUp() {
 		PropertySource<?> source = new MapPropertySource("foo", Collections.<String,Object>emptyMap());
-		Mockito.doReturn(source).when(locator).locate(Mockito.any(Environment.class));
+		doReturn(source).when(locator).locate(any(Environment.class));
 		assertEquals(Status.UP, indicator.health().getStatus());
+		verify(locator, times(1)).locate(any(Environment.class));
 	}
 
+	@Test
+	public void healthIsCached() {
+		PropertySource<?> source = new MapPropertySource("foo", Collections.<String,Object>emptyMap());
+		doReturn(source).when(locator).locate(any(Environment.class));
+
+		// not cached
+		assertEquals(Status.UP, indicator.health().getStatus());
+
+		// cached
+		assertEquals(Status.UP, indicator.health().getStatus());
+
+		verify(locator, times(1)).locate(any(Environment.class));
+	}
+
+
 }