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Apache Hadoop Common

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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.hadoop.metrics2;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * The source of metrics information. It generates and updates metrics. It
 * registers with {@link MetricsSystem}, which periodically polls it to collect
 * {@link MetricsRecord} and passes it to {@link MetricsSink}.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface MetricsSource {
  /**
   * Get metrics from the metrics source
   * @param collector to contain the resulting metrics snapshot
   * @param all if true, return all metrics even if unchanged.
   */
  void getMetrics(MetricsCollector collector, boolean all);
}