com.hazelcast.internal.metrics.impl.DoubleGaugeImpl Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2021, Hazelcast, Inc. All Rights Reserved.
*
* 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.hazelcast.internal.metrics.impl;
import com.hazelcast.internal.metrics.DoubleGauge;
import com.hazelcast.internal.metrics.DoubleProbeFunction;
import com.hazelcast.internal.metrics.LongProbeFunction;
import com.hazelcast.internal.metrics.ProbeFunction;
class DoubleGaugeImpl extends AbstractGauge implements DoubleGauge {
static final double DEFAULT_VALUE = 0d;
/**
* The value of this gauge is read out from this gauge source. Needed
* to handle static and dynamic metrics transparently for the gauge
* internals.
*
* If this gauge is created for a static metric, this is a
* {@link ProbeInstanceGaugeSource} instance, otherwise a
* {@link DoubleMetricValueCatcher} instance. The latter is used to
* catch the value of the dynamic metric this gauge is created for.
* If a static metric with metric id matching this gauge's name is
* created after creating this gauge, the
* {@link DoubleMetricValueCatcher} instance is replaced with a
* {@link ProbeInstanceGaugeSource} instance.
*/
private volatile DoubleGaugeSource gaugeSource;
DoubleGaugeImpl(MetricsRegistryImpl metricsRegistry, String name) {
super(metricsRegistry, name);
ProbeInstance probeInstance = metricsRegistry.getProbeInstance(name);
if (probeInstance != null) {
this.gaugeSource = new ProbeInstanceGaugeSource(probeInstance);
} else {
this.gaugeSource = new DoubleMetricValueCatcher();
}
}
@Override
public void onProbeInstanceSet(ProbeInstance probeInstance) {
gaugeSource = new ProbeInstanceGaugeSource(probeInstance);
}
@Override
MetricValueCatcher getCatcherOrNull() {
// we take a defensive copy, since this.gaugeSource might be changed
// between the instanceof and the casting
DoubleGaugeSource gaugeSourceCopy = this.gaugeSource;
return gaugeSourceCopy instanceof DoubleMetricValueCatcher ? (DoubleMetricValueCatcher) gaugeSourceCopy : null;
}
@Override
public double read() {
return gaugeSource.read();
}
@Override
public void render(StringBuilder stringBuilder) {
stringBuilder.append(read());
}
private static double getMetricValue(String gaugeName, Object source, ProbeFunction function,
MetricsRegistryImpl metricsRegistry) {
try {
if (function instanceof LongProbeFunction) {
LongProbeFunction longFunction = (LongProbeFunction) function;
return longFunction.get(source);
} else {
DoubleProbeFunction doubleFunction = (DoubleProbeFunction) function;
return doubleFunction.get(source);
}
} catch (Exception e) {
metricsRegistry.logger.warning("Failed to access the probe: " + gaugeName, e);
return DEFAULT_VALUE;
}
}
/**
* Local interface used to transparently back this gauge with static
* or dynamic metrics.
*
* @see #gaugeSource
*/
private interface DoubleGaugeSource {
double read();
}
private final class DoubleMetricValueCatcher extends AbstractMetricValueCatcher implements DoubleGaugeSource {
private volatile double value = DEFAULT_VALUE;
@Override
public void catchMetricValue(long collectionId, long value) {
lastCollectionId = collectionId;
this.value = value;
clearCachedMetricSourceRef();
}
@Override
public void catchMetricValue(long collectionId, double value) {
lastCollectionId = collectionId;
this.value = value;
clearCachedMetricSourceRef();
}
@Override
public double read() {
return readBase(DoubleGaugeImpl::getMetricValue, () -> value);
}
@Override
void clearCachedValue() {
value = DEFAULT_VALUE;
}
}
private final class ProbeInstanceGaugeSource implements DoubleGaugeSource {
private volatile ProbeInstance probeInstance;
private ProbeInstanceGaugeSource(ProbeInstance probeInstance) {
this.probeInstance = probeInstance;
}
@Override
public double read() {
ProbeFunction function = null;
Object source = null;
if (probeInstance != null) {
function = probeInstance.function;
source = probeInstance.source;
}
if (function == null || source == null) {
probeInstance = null;
return DEFAULT_VALUE;
}
return getMetricValue(name, source, function, metricsRegistry);
}
}
}