1 files changed, 139 insertions, 0 deletions
diff --git a/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java b/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java
new file mode 100644
index 0000000000..ee87397792
--- /dev/null
+++ b/java/com/google/gerrit/metrics/dropwizard/BucketedCallback.java
@@ -0,0 +1,139 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.metrics.dropwizard;
+
+import com.codahale.metrics.Gauge;
+import com.codahale.metrics.Metric;
+import com.codahale.metrics.MetricRegistry;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Maps;
+import com.google.gerrit.metrics.Description;
+import com.google.gerrit.metrics.Field;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/** Abstract callback metric broken down into buckets. */
+abstract class BucketedCallback<V> implements BucketedMetric {
+  private final DropWizardMetricMaker metrics;
+  private final MetricRegistry registry;
+  private final String name;
+  private final Description.FieldOrdering ordering;
+  protected final Field<?>[] fields;
+  private final V zero;
+  private final Map<Object, ValueGauge> cells;
+  protected volatile Runnable trigger;
+  private final Object lock = new Object();
+
+  BucketedCallback(
+      DropWizardMetricMaker metrics,
+      MetricRegistry registry,
+      String name,
+      Class<V> valueType,
+      Description desc,
+      Field<?>... fields) {
+    this.metrics = metrics;
+    this.registry = registry;
+    this.name = name;
+    this.ordering = desc.getFieldOrdering();
+    this.fields = fields;
+    this.zero = CallbackMetricImpl0.zeroFor(valueType);
+    this.cells = new ConcurrentHashMap<>();
+  }
+
+  void doRemove() {
+    for (Object key : cells.keySet()) {
+      registry.remove(submetric(key));
+    }
+    metrics.remove(name);
+  }
+
+  void doBeginSet() {
+    for (ValueGauge g : cells.values()) {
+      g.set = false;
+    }
+  }
+
+  void doPrune() {
+    cells.entrySet().removeIf(objectValueGaugeEntry -> !objectValueGaugeEntry.getValue().set);
+  }
+
+  void doEndSet() {
+    for (ValueGauge g : cells.values()) {
+      if (!g.set) {
+        g.value = zero;
+      }
+    }
+  }
+
+  ValueGauge getOrCreate(Object f1, Object f2) {
+    return getOrCreate(ImmutableList.of(f1, f2));
+  }
+
+  ValueGauge getOrCreate(Object f1, Object f2, Object f3) {
+    return getOrCreate(ImmutableList.of(f1, f2, f3));
+  }
+
+  ValueGauge getOrCreate(Object key) {
+    ValueGauge c = cells.get(key);
+    if (c != null) {
+      return c;
+    }
+
+    synchronized (lock) {
+      c = cells.get(key);
+      if (c == null) {
+        c = new ValueGauge();
+        registry.register(submetric(key), c);
+        cells.put(key, c);
+      }
+      return c;
+    }
+  }
+
+  private String submetric(Object key) {
+    return DropWizardMetricMaker.name(ordering, name, name(key));
+  }
+
+  abstract String name(Object key);
+
+  @Override
+  public Metric getTotal() {
+    return null;
+  }
+
+  @Override
+  public Field<?>[] getFields() {
+    return fields;
+  }
+
+  @Override
+  public Map<Object, Metric> getCells() {
+    return Maps.transformValues(cells, in -> (Metric) in);
+  }
+
+  final class ValueGauge implements Gauge<V> {
+    volatile V value = zero;
+    boolean set;
+
+    @Override
+    public V getValue() {
+      Runnable t = trigger;
+      if (t != null) {
+        t.run();
+      }
+      return value;
+    }
+  }
+}