#576 add SafepointExports

simpleclient_hotspot/src/main/java/io/prometheus/client/hotspot/DefaultExports.java

@@ -42,6 +42,7 @@ public static void register(CollectorRegistry registry) {
     new ThreadExports().register(registry);
     new ClassLoadingExports().register(registry);
     new VersionInfoExports().register(registry);
+    new SafepointExports().register(registry);
   }
 
 }

simpleclient_hotspot/src/main/java/io/prometheus/client/hotspot/SafepointExports.java

@@ -0,0 +1,61 @@
+package io.prometheus.client.hotspot;
+
+import io.prometheus.client.Collector;
+import io.prometheus.client.CounterMetricFamily;
+import sun.management.HotspotRuntimeMBean;
+import sun.management.ManagementFactoryHelper;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Exports metrics about JVM Safepoints.
+ * <p>
+ * Example usage:
+ * <pre>
+ * {@code
+ *   new SafepointExports().register();
+ * }
+ * </pre>
+ * Example metrics being exported:
+ * <pre>
+ *   jvm_safepoint_count{} 200
+ *   jvm_safepoint_total_time_seconds{} 6.7
+ *   jvm_safepoint_sync_time_seconds{} 6.7
+ * </pre>
+ */
+public class SafepointExports extends Collector {
+  private final HotspotRuntimeMBean hotspotRuntimeMBean;
+
+  public SafepointExports() {
+    this(ManagementFactoryHelper.getHotspotRuntimeMBean());
+  }
+
+  SafepointExports(HotspotRuntimeMBean hotspotRuntimeMBean) {
+    this.hotspotRuntimeMBean = hotspotRuntimeMBean;
+  }
+
+  public List<MetricFamilySamples> collect() {
+    CounterMetricFamily safepointCount = new CounterMetricFamily(
+        "jvm_safepoint_count",
+        "The number of safepoints taken place since the JVM started.",
+            hotspotRuntimeMBean.getSafepointCount());
+
+    CounterMetricFamily safepointTime = new CounterMetricFamily(
+        "jvm_safepoint_total_time_seconds",
+        "The accumulated time spent at safepoints in seconds. This is the accumulated elapsed time that the application has been stopped for safepoint operations.",
+            hotspotRuntimeMBean.getTotalSafepointTime() / MILLISECONDS_PER_SECOND);
+
+    CounterMetricFamily safepointSyncTime = new CounterMetricFamily(
+        "jvm_safepoint_sync_time_seconds",
+        "The accumulated time spent getting to safepoints in seconds.",
+            hotspotRuntimeMBean.getSafepointSyncTime() / MILLISECONDS_PER_SECOND);
+
+    List<MetricFamilySamples> mfs = new ArrayList<MetricFamilySamples>();
+    mfs.add(safepointCount);
+    mfs.add(safepointTime);
+    mfs.add(safepointSyncTime);
+
+    return mfs;
+  }
+}

simpleclient_hotspot/src/test/java/io/prometheus/client/hotspot/SafepointExportsTest.java

@@ -0,0 +1,47 @@
+package io.prometheus.client.hotspot;
+
+import io.prometheus.client.CollectorRegistry;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+import sun.management.HotspotRuntimeMBean;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.when;
+
+public class SafepointExportsTest {
+
+  private HotspotRuntimeMBean mockHotspotRuntimeBean = Mockito.mock(HotspotRuntimeMBean.class);
+  private CollectorRegistry registry = new CollectorRegistry();
+  private SafepointExports collectorUnderTest;
+
+  private static final String[] EMPTY_LABEL = new String[0];
+
+
+  @Before
+  public void setUp() {
+    when(mockHotspotRuntimeBean.getSafepointCount()).thenReturn(300L);
+    when(mockHotspotRuntimeBean.getTotalSafepointTime()).thenReturn(13L);
+    when(mockHotspotRuntimeBean.getSafepointSyncTime()).thenReturn(31L);
+    collectorUnderTest = new SafepointExports(mockHotspotRuntimeBean).register(registry);
+  }
+
+  @Test
+  public void testSafepoints() {
+    assertEquals(
+            300L,
+            registry.getSampleValue(
+                    "jvm_safepoint_count", EMPTY_LABEL, EMPTY_LABEL),
+            .0000001);
+    assertEquals(
+            0.013,
+            registry.getSampleValue(
+                    "jvm_safepoint_total_time_seconds", EMPTY_LABEL, EMPTY_LABEL),
+            .0000001);
+    assertEquals(
+            0.031,
+            registry.getSampleValue(
+                    "jvm_safepoint_sync_time_seconds", EMPTY_LABEL, EMPTY_LABEL),
+            .0000001);
+  }
+}