Add systemload.average to SystemPublicMetrics

Fixes gh-1865

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/SystemPublicMetrics.java

@@ -35,6 +35,7 @@ import org.springframework.util.StringUtils;
  * @author Dave Syer
  * @author Christian Dupuis
  * @author Stephane Nicoll
+ * @author Johannes Stelzer
  * @since 1.2.0
  */
 public class SystemPublicMetrics implements PublicMetrics, Ordered {
@@ -74,6 +75,8 @@ public class SystemPublicMetrics implements PublicMetrics, Ordered {
 				.getUptime()));
 		result.add(new Metric<Long>("instance.uptime", System.currentTimeMillis()
 				- this.timestamp));
+		result.add(new Metric<Double>("systemload.average", ManagementFactory
+				.getOperatingSystemMXBean().getSystemLoadAverage()));
 	}
 
 	/**

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/SystemPublicMetricsTests.java

@@ -42,6 +42,7 @@ public class SystemPublicMetricsTests {
 		assertTrue(results.containsKey("mem.free"));
 		assertTrue(results.containsKey("processors"));
 		assertTrue(results.containsKey("uptime"));
+		assertTrue(results.containsKey("systemload.average"));
 
 		assertTrue(results.containsKey("heap.committed"));
 		assertTrue(results.containsKey("heap.init"));