Metric.java

/*
 * Copyright (c) 2008-2017, 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;

/**
 * A Metric is a 'quantitative measure' of something for example the number of operations pending, number of operations
 * per second being executed etc.
 *
 * Each metric is uniquely identified using a name. See {@link #getName()}.
 *
 * A metric gets its content from a probe. An probe can be one of the following:
 * <ol>
 *     <li>a method with the {@link Probe} annotation</li>
 *     <li>a field with the {@link Probe} annotation</li>
 *     <li>a {@link LongProbeFunction}</li>
 *     <li>a {@link DoubleProbeFunction}</li>
 * </ol>
 *
 * If the Metric is obtained before a probe is registered, the Metric is without probe. As long as no probe is available,
 * every time the metrics needs a value, it will look up the probe in the {@link MetricsRegistry}.
 */
public interface Metric {

    /**
     * Gets the name that identifies this metric.
     *
     * The returned value will never change and never be null.
     *
     * @return the name of the metric.
     */
    String getName();
}