HBASE-8556 fix coverage org.apache.hadoop.hbase.metrics.histogram (Aleksey Gorshkov)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1537436 13f79535-47bb-0310-9956-ffa450edef68

hbase-server/src/test/java/org/apache/hadoop/hbase/metrics/TestMetricsHistogram.java

@@ -0,0 +1,112 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.hadoop.hbase.metrics;
+
+import static org.mockito.Matchers.anyFloat;
+import static org.mockito.Matchers.anyLong;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import java.util.Random;
+
+import org.apache.hadoop.hbase.SmallTests;
+import org.apache.hadoop.hbase.metrics.histogram.MetricsHistogram;
+import org.apache.hadoop.metrics.MetricsRecord;
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import com.yammer.metrics.stats.Snapshot;
+
+@SuppressWarnings("deprecation")
+@Category(SmallTests.class)
+public class TestMetricsHistogram {
+
+  @Test
+  public void testBasicUniform() {
+    MetricsHistogram h = new MetricsHistogram("testHistogram", null);
+
+    for (int i = 0; i < 100; i++) {
+      h.update(i);
+    }
+
+    Assert.assertEquals(100, h.getCount());
+    Assert.assertEquals(0, h.getMin());
+    Assert.assertEquals(99, h.getMax());
+    Assert.assertEquals(49.5d, h.getMean(), 0.01);
+  }
+
+  @Test
+  public void testSnapshotPercentiles() {
+    final MetricsHistogram h = new MetricsHistogram("testHistogram", null);
+    final long[] data = genRandomData(h);
+
+    final Snapshot s = h.getSnapshot();
+
+    assertPercentile(data, 50, s.getMedian());
+    assertPercentile(data, 75, s.get75thPercentile());
+    assertPercentile(data, 95, s.get95thPercentile());
+    assertPercentile(data, 98, s.get98thPercentile());
+    assertPercentile(data, 99, s.get99thPercentile());
+    assertPercentile(data, 99.9, s.get999thPercentile());
+  }
+
+  @Test
+  public void testPushMetric() {
+    final MetricsHistogram h = new MetricsHistogram("testHistogram", null);
+    genRandomData(h);
+
+    MetricsRecord mr = mock(MetricsRecord.class);
+    h.pushMetric(mr);
+    
+    verify(mr).setMetric("testHistogram_num_ops", 10000L);
+    verify(mr).setMetric(eq("testHistogram_min"), anyLong());
+    verify(mr).setMetric(eq("testHistogram_max"), anyLong());
+    verify(mr).setMetric(eq("testHistogram_mean"), anyFloat());
+    verify(mr).setMetric(eq("testHistogram_std_dev"), anyFloat());
+    verify(mr).setMetric(eq("testHistogram_median"), anyFloat());
+    verify(mr).setMetric(eq("testHistogram_75th_percentile"), anyFloat());
+    verify(mr).setMetric(eq("testHistogram_95th_percentile"), anyFloat());
+    verify(mr).setMetric(eq("testHistogram_99th_percentile"), anyFloat());    
+  }
+
+  private void assertPercentile(long[] data, double percentile, double value) {
+    int count = 0;
+    for (long v : data) {
+      if (v < value) {
+        count++;
+      }
+    }
+    Assert.assertEquals("Wrong " + percentile + " percentile", 
+        (int)(percentile / 100), count / data.length);
+  }
+  
+  private long[] genRandomData(final MetricsHistogram h) {
+    final Random r = new Random();
+    final long[] data = new long[10000];
+
+    for (int i = 0; i < data.length; i++) {
+      data[i] = (long) (r.nextGaussian() * 10000);
+      h.update(data[i]);
+    }
+    
+    return data;
+  }
+  
+}