Line data    Source code

       1             : // Copyright (C) 2015 The Android Open Source Project
       2             : //
       3             : // Licensed under the Apache License, Version 2.0 (the "License");
       4             : // you may not use this file except in compliance with the License.
       5             : // You may obtain a copy of the License at
       6             : //
       7             : // http://www.apache.org/licenses/LICENSE-2.0
       8             : //
       9             : // Unless required by applicable law or agreed to in writing, software
      10             : // distributed under the License is distributed on an "AS IS" BASIS,
      11             : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      12             : // See the License for the specific language governing permissions and
      13             : // limitations under the License.
      14             : 
      15             : package com.google.gerrit.metrics.dropwizard;
      16             : 
      17             : import com.google.common.collect.ImmutableSet;
      18             : import java.util.concurrent.TimeUnit;
      19             : import java.util.concurrent.atomic.AtomicLong;
      20             : 
      21             : /**
      22             :  * Run a user specified trigger only once every 2 seconds.
      23             :  *
      24             :  * <p>This allows the same Runnable trigger to be applied to several metrics. When a recorder is
      25             :  * sampling the related metrics only the first access will perform recomputation. Reading other
      26             :  * related metrics will rely on the already set values for the next several seconds.
      27             :  */
      28             : class CallbackGroup implements Runnable {
      29          16 :   private static final long PERIOD = TimeUnit.SECONDS.toNanos(2);
      30             : 
      31             :   private final AtomicLong reloadAt;
      32             :   private final Runnable trigger;
      33             :   private final ImmutableSet<CallbackMetricGlue> metrics;
      34          16 :   private final Object reloadLock = new Object();
      35             : 
      36          16 :   CallbackGroup(Runnable trigger, ImmutableSet<CallbackMetricGlue> metrics) {
      37          16 :     this.reloadAt = new AtomicLong(0);
      38          16 :     this.trigger = trigger;
      39          16 :     this.metrics = metrics;
      40          16 :   }
      41             : 
      42             :   @Override
      43             :   public void run() {
      44          16 :     if (reload()) {
      45          16 :       synchronized (reloadLock) {
      46          16 :         for (CallbackMetricGlue m : metrics) {
      47          16 :           m.beginSet();
      48          16 :         }
      49          16 :         trigger.run();
      50          16 :         for (CallbackMetricGlue m : metrics) {
      51          16 :           m.endSet();
      52          16 :         }
      53          16 :       }
      54             :     }
      55          16 :   }
      56             : 
      57             :   private boolean reload() {
      58             :     for (; ; ) {
      59          16 :       long now = System.nanoTime();
      60          16 :       long next = reloadAt.get();
      61          16 :       if (next > now) {
      62           1 :         return false;
      63          16 :       } else if (reloadAt.compareAndSet(next, now + PERIOD)) {
      64          16 :         return true;
      65             :       }
      66           0 :     }
      67             :   }
      68             : }