Add statsd metric export auto-configuration

Update MetricExportAutoConfiguration to auto-configure statsd metrics
export when a `spring.metrics.export.statsd.host` property is set.

Closes gh-3719

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/autoconfigure/MetricExportAutoConfiguration.java

@@ -29,6 +29,7 @@ import org.springframework.boot.actuate.metrics.export.MetricExportProperties;
 import org.springframework.boot.actuate.metrics.export.MetricExporters;
 import org.springframework.boot.actuate.metrics.reader.CompositeMetricReader;
 import org.springframework.boot.actuate.metrics.reader.MetricReader;
+import org.springframework.boot.actuate.metrics.statsd.StatsdMetricWriter;
 import org.springframework.boot.actuate.metrics.writer.MetricWriter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
@@ -45,6 +46,7 @@ import org.springframework.util.CollectionUtils;
  * {@link EnableAutoConfiguration Auto-configuration} for metrics export.
  *
  * @author Dave Syer
+ * @author Simon Buettner
  * @since 1.3.0
  */
 @Configuration
@@ -92,6 +94,16 @@ public class MetricExportAutoConfiguration {
 		return exporters;
 	}
 
+	@Bean
+	@ExportMetricWriter
+	@ConditionalOnMissingBean
+	@ConditionalOnProperty(prefix = "spring.metrics.export.statsd", name = "host")
+	public StatsdMetricWriter statsdMetricWriter() {
+		MetricExportProperties.Statsd statsdProperties = this.properties.getStatsd();
+		return new StatsdMetricWriter(statsdProperties.getPrefix(),
+				statsdProperties.getHost(), statsdProperties.getPort());
+	}
+
 	@Configuration
 	protected static class MetricExportPropertiesConfiguration {
 

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/export/MetricExportProperties.java

@@ -29,6 +29,7 @@ import org.springframework.util.PatternMatchUtils;
  * Configuration properties for metrics export.
  *
  * @author Dave Syer
+ * @author Simon Buettner
  * @since 1.3.0
  */
 @ConfigurationProperties("spring.metrics.export")
@@ -43,6 +44,8 @@ public class MetricExportProperties extends TriggerProperties {
 
 	private Redis redis = new Redis();
 
+	private Statsd statsd = new Statsd();
+
 	@PostConstruct
 	public void setUpDefaults() {
 		TriggerProperties defaults = this;
@@ -79,10 +82,6 @@ public class MetricExportProperties extends TriggerProperties {
 		return this.triggers;
 	}
 
-	public Redis getRedis() {
-		return this.redis;
-	}
-
 	public Aggregate getAggregate() {
 		return this.aggregate;
 	}
@@ -91,10 +90,22 @@ public class MetricExportProperties extends TriggerProperties {
 		this.aggregate = aggregate;
 	}
 
+	public Redis getRedis() {
+		return this.redis;
+	}
+
 	public void setRedis(Redis redis) {
 		this.redis = redis;
 	}
 
+	public Statsd getStatsd() {
+		return this.statsd;
+	}
+
+	public void setStatsd(Statsd statsd) {
+		this.statsd = statsd;
+	}
+
 	/**
 	 * Find a matching trigger configuration.
 	 * @param name the bean name to match
@@ -205,4 +216,50 @@ public class MetricExportProperties extends TriggerProperties {
 
 	}
 
+	/**
+	 * Statsd properties.
+	 */
+	public static class Statsd {
+
+		/**
+		 * Host of a statsd server to receive exported metrics.
+		 */
+		private String host;
+
+		/**
+		 * Port of a statsd server to receive exported metrics.
+		 */
+		private int port = 8125;
+
+		/**
+		 * Prefix for statsd exported metrics.
+		 */
+		private String prefix;
+
+		public String getHost() {
+			return this.host;
+		}
+
+		public void setHost(String host) {
+			this.host = host;
+		}
+
+		public int getPort() {
+			return this.port;
+		}
+
+		public void setPort(int port) {
+			this.port = port;
+		}
+
+		public String getPrefix() {
+			return this.prefix;
+		}
+
+		public void setPrefix(String prefix) {
+			this.prefix = prefix;
+		}
+
+	}
+
 }

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/autoconfigure/MetricExportAutoConfigurationTests.java

@@ -17,16 +17,21 @@
 package org.springframework.boot.actuate.autoconfigure;
 
 import org.junit.After;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.mockito.Matchers;
 import org.mockito.Mockito;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.boot.actuate.endpoint.MetricsEndpointMetricReader;
 import org.springframework.boot.actuate.metrics.GaugeService;
 import org.springframework.boot.actuate.metrics.Metric;
 import org.springframework.boot.actuate.metrics.export.MetricCopyExporter;
 import org.springframework.boot.actuate.metrics.export.MetricExporters;
+import org.springframework.boot.actuate.metrics.statsd.StatsdMetricWriter;
 import org.springframework.boot.actuate.metrics.writer.MetricWriter;
 import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -36,16 +41,22 @@ import org.springframework.messaging.MessageHandler;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.SubscribableChannel;
 
+import static org.hamcrest.Matchers.notNullValue;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
 
 /**
  * Tests for {@link MetricExportAutoConfiguration}.
  *
  * @author Phillip Webb
  * @author Dave Syer
+ * @author Simon Buettner
  */
 public class MetricExportAutoConfigurationTests {
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	private AnnotationConfigApplicationContext context;
 
 	@After
@@ -100,16 +111,43 @@ public class MetricExportAutoConfigurationTests {
 		Mockito.verify(reader, Mockito.atLeastOnce()).findAll();
 	}
 
+	@Test
+	public void statsdMissingHost() throws Exception {
+		this.context = new AnnotationConfigApplicationContext();
+		this.context.register(WriterConfig.class, MetricEndpointConfiguration.class,
+				MetricExportAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class);
+		this.context.refresh();
+		this.thrown.expect(NoSuchBeanDefinitionException.class);
+		this.context.getBean(StatsdMetricWriter.class);
+	}
+
+	@Test
+	public void statsdWithHost() throws Exception {
+		this.context = new AnnotationConfigApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.metrics.export.statsd.host=localhost");
+		this.context.register(WriterConfig.class, MetricEndpointConfiguration.class,
+				MetricExportAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class);
+		this.context.refresh();
+		assertThat(this.context.getBean(StatsdMetricWriter.class), notNullValue());
+	}
+
 	@Configuration
 	public static class MessageChannelConfiguration {
+
 		@Bean
 		public SubscribableChannel metricsChannel() {
 			return new FixedSubscriberChannel(new MessageHandler() {
+
 				@Override
 				public void handleMessage(Message<?> message) throws MessagingException {
 				}
+
 			});
 		}
+
 	}
 
 	@Configuration

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -790,6 +790,9 @@ content into your application; rather pick only the properties that you need.
 	spring.metrics.export.excludes= # list of patterns for metric names to exclude. Applied after the includes
 	spring.metrics.export.redis.prefix=spring.metrics # prefix for redis repository if active
 	spring.metrics.export.redis.key=keys.spring.metrics # key for redis repository export (if active)
+	spring.metrics.export.statsd.host= # host of the statsd server
+	spring.metrics.export.statsd.port=8125 # port of the statsd server
+	spring.metrics.export.statsd.prefix= # prefix for exported metrics
 	spring.metrics.export.triggers.*= # specific trigger properties per MetricWriter bean name
 
 	# SENDGRID ({sc-spring-boot-autoconfigure}/sendgrid/SendGridAutoConfiguration.{sc-ext}[SendGridAutoConfiguration])

spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -1142,28 +1142,28 @@ curl localhost:4242/api/query?start=1h-ago&m=max:counter.status.200.root
 
 [[production-ready-metric-writers-export-to-statsd]]
 ==== Example: Export to Statsd
-If you provide a `@Bean` of type `StatsdMetricWriter` and mark it `@ExportMetricWriter` the metrics are exported to a
-statsd server:
+To export metrics to Statsd add a `spring.metrics.export.statsd.host` value to your
+`application.properties` file. Connections will be opened to port `8125` unless a
+`spring.metrics.export.statsd.port` override is provided. You can use
+`spring.metrics.export.statsd.prefix` if you want a custom prefix.
+
+Alternatively, you can provide a `@Bean` of type `StatsdMetricWriter` and mark it
+`@ExportMetricWriter`:
 
 [source,java,indent=0]
 ----
 @Value("${spring.application.name:application}.${random.value:0000}")
 private String prefix = "metrics";
 
-@Value("${statsd.host:localhost}")
-private String host = "localhost";
-
-@Value("${statsd.port:8125}")
-private int port;
-
 @Bean
 @ExportMetricWriter
 MetricWriter metricWriter() {
-	return new StatsdMetricWriter(prefix, host, port);
+	return new StatsdMetricWriter(prefix, "localhost", "8125");
 }
 ----
 
 
+
 [[production-ready-metric-writers-export-to-jmx]]
 ==== Example: Export to JMX
 If you provide a `@Bean` of type `JmxMetricWriter` marked `@ExportMetricWriter` the metrics are exported as MBeans to