/**
 * 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.hbase.regionserver;

import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.metrics.BaseSourceImpl;
import org.apache.hadoop.hbase.metrics.Interns;
import org.apache.hadoop.metrics2.MetricsCollector;
import org.apache.hadoop.metrics2.MetricsRecordBuilder;
import org.apache.hadoop.metrics2.impl.JmxCacheBuster;
import org.apache.hadoop.metrics2.lib.MetricsExecutorImpl;

@InterfaceAudience.Private
public class MetricsRegionAggregateSourceImpl extends BaseSourceImpl
    implements MetricsRegionAggregateSource {

  private static final Log LOG = LogFactory.getLog(MetricsRegionAggregateSourceImpl.class);

  private final MetricsExecutorImpl executor = new MetricsExecutorImpl();

  private final Set<MetricsRegionSource> regionSources =
      Collections.newSetFromMap(new ConcurrentHashMap<MetricsRegionSource, Boolean>());

  public MetricsRegionAggregateSourceImpl() {
    this(METRICS_NAME, METRICS_DESCRIPTION, METRICS_CONTEXT, METRICS_JMX_CONTEXT);
  }


  public MetricsRegionAggregateSourceImpl(String metricsName,
                                          String metricsDescription,
                                          String metricsContext,
                                          String metricsJmxContext) {
    super(metricsName, metricsDescription, metricsContext, metricsJmxContext);

    // Every few mins clean the JMX cache.
    executor.getExecutor().scheduleWithFixedDelay(new Runnable() {
      public void run() {
        JmxCacheBuster.clearJmxCache();
      }
    }, 5, 5, TimeUnit.MINUTES);
  }

  @Override
  public void register(MetricsRegionSource source) {
    regionSources.add(source);
    clearCache();
  }

  @Override
  public void deregister(MetricsRegionSource toRemove) {
    try {
      regionSources.remove(toRemove);
    } catch (Exception e) {
      // Ignored. If this errors out it means that someone is double
      // closing the region source and the region is already nulled out.
      LOG.info(
          "Error trying to remove " + toRemove + " from " + this.getClass().getSimpleName(),
          e);
    }
    clearCache();
  }

  private synchronized void clearCache() {
    JmxCacheBuster.clearJmxCache();
  }

  /**
   * Yes this is a get function that doesn't return anything.  Thanks Hadoop for breaking all
   * expectations of java programmers.  Instead of returning anything Hadoop metrics expects
   * getMetrics to push the metrics into the collector.
   *
   * @param collector the collector
   * @param all       get all the metrics regardless of when they last changed.
   */
  @Override
  public void getMetrics(MetricsCollector collector, boolean all) {
    MetricsRecordBuilder mrb = collector.addRecord(metricsName);

    if (regionSources != null) {
      for (MetricsRegionSource regionMetricSource : regionSources) {
        if (regionMetricSource instanceof MetricsRegionSourceImpl) {
          ((MetricsRegionSourceImpl) regionMetricSource).snapshot(mrb, all);
        }
      }
      mrb.addGauge(Interns.info(NUM_REGIONS, NUMBER_OF_REGIONS_DESC), regionSources.size());
      metricsRegistry.snapshot(mrb, all);
    }
  }
}