org.apache.sling.commons.metrics.Gauge Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.sling.commons.metrics;
import org.osgi.annotation.versioning.ConsumerType;
/**
* A gauge metric is an instantaneous reading of a particular value. To instrument a queue's depth,
* for example:
*
* final Queue<String> queue = new ConcurrentLinkedQueue<String>();
* final Gauge<Integer> queueDepth = new Gauge<Integer>() {
* public Integer getValue() {
* return queue.size();
* }
* };
*
*
* A Gauge instance should be registered with OSGi ServiceRegistry with {@code Gauge#NAME} set
* to Gauge name. Then the Gauge instance would be registered with MetricService via whiteboard
* pattern
*
* @param the type of the metric's value
*/
@ConsumerType
public interface Gauge {
/**
* Service property name which determines the name of the Gauge
*/
String NAME = "name";
/**
* Returns the metric's current value.
*
* @return the metric's current value
*/
T getValue();
}