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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.hbase.regionserver;

import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceAudience;

/**
 * A {@link FlushPolicy} that only flushes store larger a given threshold. If no store is large
 * enough, then all stores will be flushed.
 */
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
public class FlushLargeStoresPolicy extends FlushPolicy {

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

  public static final String HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND =
      "hbase.hregion.percolumnfamilyflush.size.lower.bound";

  private static final long DEFAULT_HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND = 1024 * 1024 * 16L;

  private long flushSizeLowerBound;

  @Override
  protected void configureForRegion(HRegion region) {
    super.configureForRegion(region);
    long flushSizeLowerBound;
    String flushedSizeLowerBoundString =
        region.getTableDesc().getValue(HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND);
    if (flushedSizeLowerBoundString == null) {
      flushSizeLowerBound =
          getConf().getLong(HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND,
            DEFAULT_HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND);
      if (LOG.isDebugEnabled()) {
        LOG.debug(HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND
            + " is not specified, use global config(" + flushSizeLowerBound + ") instead");
      }
    } else {
      try {
        flushSizeLowerBound = Long.parseLong(flushedSizeLowerBoundString);
      } catch (NumberFormatException nfe) {
        flushSizeLowerBound =
            getConf().getLong(HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND,
              DEFAULT_HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND);
        LOG.warn("Number format exception when parsing "
            + HREGION_COLUMNFAMILY_FLUSH_SIZE_LOWER_BOUND + " for table "
            + region.getTableDesc().getTableName() + ":" + flushedSizeLowerBoundString + ". " + nfe
            + ", use global config(" + flushSizeLowerBound + ") instead");

      }
    }
    this.flushSizeLowerBound = flushSizeLowerBound;
  }

  private boolean shouldFlush(Store store) {
    if (store.getMemStoreSize() > this.flushSizeLowerBound) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Flush Column Family " + store.getColumnFamilyName() + " of " +
          region.getRegionInfo().getEncodedName() + " because memstoreSize=" +
          store.getMemStoreSize() + " > lower bound=" + this.flushSizeLowerBound);
      }
      return true;
    }
    return region.shouldFlushStore(store);
  }

  @Override
  public Collection selectStoresToFlush() {
    Collection stores = region.stores.values();
    Set specificStoresToFlush = new HashSet();
    for (Store store : stores) {
      if (shouldFlush(store)) {
        specificStoresToFlush.add(store);
      }
    }
    // Didn't find any CFs which were above the threshold for selection.
    if (specificStoresToFlush.isEmpty()) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Since none of the CFs were above the size, flushing all.");
      }
      return stores;
    } else {
      return specificStoresToFlush;
    }
  }

}