com.netflix.servo.monitor.MinGauge Maven / Gradle / Ivy
/**
* Copyright 2013 Netflix, Inc.
*
* 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.netflix.servo.monitor;
import com.netflix.servo.annotations.DataSourceType;
import com.netflix.servo.util.Clock;
import com.netflix.servo.util.ClockWithOffset;
import java.util.concurrent.atomic.AtomicLong;
/**
* Gauge that keeps track of the minimum value seen since the last reset. The reset value is
* Long.MAX_VALUE. If no update has been received since the last reset, then {@link #getValue}
* will return 0.
*/
public class MinGauge extends AbstractMonitor
implements Gauge {
private final StepLong min;
/**
* Creates a new instance of the gauge.
*/
public MinGauge(MonitorConfig config) {
this(config, ClockWithOffset.INSTANCE);
}
/**
* Creates a new instance of the gauge using a specific Clock. Useful for unit testing.
*/
MinGauge(MonitorConfig config, Clock clock) {
super(config.withAdditionalTag(DataSourceType.GAUGE));
min = new StepLong(Long.MAX_VALUE, clock);
}
private void updateMin(int idx, long v) {
AtomicLong current = min.getCurrent(idx);
long m = current.get();
while (v < m) {
if (current.compareAndSet(m, v)) {
break;
}
m = current.get();
}
}
/**
* Update the min if the provided value is smaller than the current min.
*/
public void update(long v) {
for (int i = 0; i < Pollers.NUM_POLLERS; ++i) {
updateMin(i, v);
}
}
/**
* {@inheritDoc}
*/
@Override
public Long getValue(int pollerIdx) {
long v = min.poll(pollerIdx);
return (v == Long.MAX_VALUE) ? 0L : v;
}
/**
* Returns the current min value since the last reset.
*/
public long getCurrentValue(int nth) {
long v = min.getCurrent(nth).get();
return (v == Long.MAX_VALUE) ? 0L : v;
}
/**
* {@inheritDoc}
*/
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj == null || !(obj instanceof MinGauge)) {
return false;
}
MinGauge m = (MinGauge) obj;
return config.equals(m.getConfig()) && getValue(0).equals(m.getValue(0));
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
int result = getConfig().hashCode();
result = 31 * result + getValue(0).hashCode();
return result;
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
return "MinGauge{config=" + config + ", min=" + min + '}';
}
}