001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.metrics2;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022import org.apache.hadoop.classification.InterfaceStability;
023
024/**
025 * The source of metrics information. It generates and updates metrics. It
026 * registers with {@link MetricsSystem}, which periodically polls it to collect
027 * {@link MetricsRecord} and passes it to {@link MetricsSink}.
028 */
029@InterfaceAudience.Public
030@InterfaceStability.Evolving
031public interface MetricsSource {
032  /**
033   * Get metrics from the metrics source
034   * @param collector to contain the resulting metrics snapshot
035   * @param all if true, return all metrics even if unchanged.
036   */
037  void getMetrics(MetricsCollector collector, boolean all);
038}