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/*
* Copyright 2018, OpenCensus Authors
*
* 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 io.opencensus.metrics;
import io.opencensus.internal.Utils;
import java.util.List;
import javax.annotation.concurrent.ThreadSafe;
/**
* Double Gauge metric, to report instantaneous measurement of a double value. Gauges can go both up
* and down. The gauges values can be negative.
*
* <p>Example 1: Create a Gauge with default labels.
*
* <pre>{@code
* class YourClass {
*
* private static final MetricRegistry metricRegistry = Metrics.getMetricRegistry();
*
* List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
* // TODO(mayurkale): Plugs-in the DoubleGauge into the registry.
* DoubleGauge gauge = metricRegistry.addDoubleGauge("queue_size",
* "Pending jobs", "1", labelKeys);
*
* // It is recommended to keep a reference of a point for manual operations.
* DoublePoint defaultPoint = gauge.getDefaultTimeSeries();
*
* void doWork() {
* // Your code here.
* defaultPoint.add(10);
* }
*
* }
* }</pre>
*
* <p>Example 2: You can also use labels(keys and values) to track different types of metric.
*
* <pre>{@code
* class YourClass {
*
* private static final MetricRegistry metricRegistry = Metrics.getMetricRegistry();
*
* List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
* List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));
*
* // TODO(mayurkale): Plugs-in the DoubleGauge into the registry.
* DoubleGauge gauge = metricRegistry.addDoubleGauge("queue_size",
* "Pending jobs", "1", labelKeys);
*
* // It is recommended to keep a reference of a point for manual operations.
* DoublePoint inboundPoint = gauge.getOrCreateTimeSeries(labelValues);
*
* void doSomeWork() {
* // Your code here.
* inboundPoint.set(15);
* }
*
* }
* }</pre>
*
* @since 0.17
*/
@ThreadSafe
public abstract class DoubleGauge {
/**
* Creates a {@code TimeSeries} and returns a {@code DoublePoint} if the specified {@code
* labelValues} is not already associated with this gauge, else returns an existing {@code
* DoublePoint}.
*
* <p>It is recommended to keep a reference to the DoublePoint instead of always calling this
* method for manual operations.
*
* @param labelValues the list of label values. The number of label values must be the same to
* that of the label keys.
* @return a {@code DoublePoint} the value of single gauge.
* @throws NullPointerException if {@code labelValues} is null OR any element of {@code
* labelValues} is null.
* @throws IllegalArgumentException if number of {@code labelValues}s are not equal to the label
* keys.
* @since 0.17
*/
public abstract DoublePoint getOrCreateTimeSeries(List<LabelValue> labelValues);
/**
* Returns a {@code DoublePoint} for a gauge with all labels not set, or default labels.
*
* @return a {@code DoublePoint} for a gauge with all labels not set, or default labels.
* @since 0.17
*/
public abstract DoublePoint getDefaultTimeSeries();
/**
* Removes the {@code TimeSeries} from the gauge metric, if it is present. i.e. references to
* previous {@code DoublePoint} objects are invalid (not part of the metric).
*
* @param labelValues the list of label values.
* @throws NullPointerException if {@code labelValues} is null or any element of {@code
* labelValues} is null.
* @since 0.17
*/
public abstract void removeTimeSeries(List<LabelValue> labelValues);
/**
* Removes all {@code TimeSeries} from the gauge metric. i.e. references to all previous {@code
* DoublePoint} objects are invalid (not part of the metric).
*
* @since 0.17
*/
public abstract void clear();
/**
* Returns the no-op implementation of the {@code DoubleGauge}.
*
* @return the no-op implementation of the {@code DoubleGauge}.
* @since 0.17
*/
static DoubleGauge newNoopDoubleGauge(
String name, String description, String unit, List<LabelKey> labelKeys) {
return NoopDoubleGauge.create(name, description, unit, labelKeys);
}
/**
* The value of a single point in the Gauge.TimeSeries.
*
* @since 0.17
*/
public abstract static class DoublePoint {
/**
* Adds the given value to the current value. The values can be negative.
*
* @param amt the value to add
* @since 0.17
*/
public abstract void add(double amt);
/**
* Sets the given value.
*
* @param val the new value.
* @since 0.17
*/
public abstract void set(double val);
}
/** No-op implementations of DoubleGauge class. */
private static final class NoopDoubleGauge extends DoubleGauge {
private final int labelKeysSize;
static NoopDoubleGauge create(
String name, String description, String unit, List<LabelKey> labelKeys) {
return new NoopDoubleGauge(name, description, unit, labelKeys);
}
/** Creates a new {@code NoopDoublePoint}. */
NoopDoubleGauge(String name, String description, String unit, List<LabelKey> labelKeys) {
Utils.checkNotNull(name, "name");
Utils.checkNotNull(description, "description");
Utils.checkNotNull(unit, "unit");
Utils.checkListElementNotNull(
Utils.checkNotNull(labelKeys, "labelKeys"), "labelKey element should not be null.");
labelKeysSize = labelKeys.size();
}
@Override
public NoopDoublePoint getOrCreateTimeSeries(List<LabelValue> labelValues) {
Utils.checkListElementNotNull(
Utils.checkNotNull(labelValues, "labelValues"), "labelValue element should not be null.");
Utils.checkArgument(labelKeysSize == labelValues.size(), "Incorrect number of labels.");
return NoopDoublePoint.INSTANCE;
}
@Override
public NoopDoublePoint getDefaultTimeSeries() {
return NoopDoublePoint.INSTANCE;
}
@Override
public void removeTimeSeries(List<LabelValue> labelValues) {
Utils.checkNotNull(labelValues, "labelValues");
}
@Override
public void clear() {}
/** No-op implementations of DoublePoint class. */
private static final class NoopDoublePoint extends DoublePoint {
private static final NoopDoublePoint INSTANCE = new NoopDoublePoint();
private NoopDoublePoint() {}
@Override
public void add(double amt) {}
@Override
public void set(double val) {}
}
}
}
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