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// 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.google.common.collect.ImmutableSet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* Run a user specified trigger only once every 2 seconds.
*
* <p>This allows the same Runnable trigger to be applied to several metrics. When a recorder is
* sampling the related metrics only the first access will perform recomputation. Reading other
* related metrics will rely on the already set values for the next several seconds.
*/
class CallbackGroup implements Runnable {
private static final long PERIOD = TimeUnit.SECONDS.toNanos(2);
private final AtomicLong reloadAt;
private final Runnable trigger;
private final ImmutableSet<CallbackMetricGlue> metrics;
private final Object reloadLock = new Object();
CallbackGroup(Runnable trigger, ImmutableSet<CallbackMetricGlue> metrics) {
this.reloadAt = new AtomicLong(0);
this.trigger = trigger;
this.metrics = metrics;
}
@Override
public void run() {
if (reload()) {
synchronized (reloadLock) {
for (CallbackMetricGlue m : metrics) {
m.beginSet();
}
trigger.run();
for (CallbackMetricGlue m : metrics) {
m.endSet();
}
}
}
}
private boolean reload() {
for (; ; ) {
long now = System.nanoTime();
long next = reloadAt.get();
if (next > now) {
return false;
} else if (reloadAt.compareAndSet(next, now + PERIOD)) {
return true;
}
}
}
}
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