HBASE-11573 Report age on eviction; ADD FORGOTTEN FILE

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/AgeSnapshot.java

@@ -0,0 +1,74 @@
+/**
+ * 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.io.hfile;
+
+import org.codehaus.jackson.annotate.JsonIgnoreProperties;
+
+import com.yammer.metrics.core.Histogram;
+import com.yammer.metrics.stats.Snapshot;
+
+/**
+ * Snapshot of block cache age in cache.
+ * This object is preferred because we can control how it is serialized out when JSON'ing.
+ */
+@JsonIgnoreProperties({"ageHistogram", "snapshot"})
+public class AgeSnapshot {
+  private final Histogram ageHistogram;
+  private final Snapshot snapshot;
+
+  AgeSnapshot(final Histogram ageHistogram) {
+    this.ageHistogram = ageHistogram;
+    this.snapshot = ageHistogram.getSnapshot();
+  }
+
+  public double get75thPercentile() {
+    return snapshot.get75thPercentile();
+  }
+
+  public double get95thPercentile() {
+    return snapshot.get95thPercentile();
+  }
+
+  public double get98thPercentile() {
+    return snapshot.get98thPercentile();
+  }
+
+  public double get999thPercentile() {
+    return snapshot.get999thPercentile();
+  }
+
+  public double get99thPercentile() {
+    return snapshot.get99thPercentile();
+  }
+
+  public double getMean() {
+    return this.ageHistogram.mean();
+  }
+
+  public double getMax() {
+    return ageHistogram.max();
+  }
+
+  public double getMin() {
+    return ageHistogram.min();
+  }
+
+  public double getStdDev() {
+    return ageHistogram.stdDev();
+  }
+}