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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.compactions;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.regionserver.StoreConfigInformation;
import org.apache.hadoop.hbase.regionserver.StoreFile;
/**
* Class to pick which files if any to compact together.
*
* This class will search all possibilities for different and if it gets stuck it will choose
* the smallest set of files to compact.
*/
@InterfaceAudience.Private
public class ExploringCompactionPolicy extends RatioBasedCompactionPolicy {
private static final Log LOG = LogFactory.getLog(ExploringCompactionPolicy.class);
/**
* Constructor for ExploringCompactionPolicy.
* @param conf The configuration object
* @param storeConfigInfo An object to provide info about the store.
*/
public ExploringCompactionPolicy(final Configuration conf,
final StoreConfigInformation storeConfigInfo) {
super(conf, storeConfigInfo);
}
@Override
final ArrayList applyCompactionPolicy(final ArrayList candidates,
final boolean mayUseOffPeak, final boolean mightBeStuck) throws IOException {
return new ArrayList(applyCompactionPolicy(candidates, mightBeStuck,
mayUseOffPeak, comConf.getMinFilesToCompact(), comConf.getMaxFilesToCompact()));
}
public List applyCompactionPolicy(final List candidates,
boolean mightBeStuck, boolean mayUseOffPeak, int minFiles, int maxFiles) {
final double currentRatio = mayUseOffPeak
? comConf.getCompactionRatioOffPeak() : comConf.getCompactionRatio();
// Start off choosing nothing.
List bestSelection = new ArrayList(0);
List smallest = mightBeStuck ? new ArrayList(0) : null;
long bestSize = 0;
long smallestSize = Long.MAX_VALUE;
int opts = 0, optsInRatio = 0, bestStart = -1; // for debug logging
// Consider every starting place.
for (int start = 0; start < candidates.size(); start++) {
// Consider every different sub list permutation in between start and end with min files.
for (int currentEnd = start + minFiles - 1;
currentEnd < candidates.size(); currentEnd++) {
List potentialMatchFiles = candidates.subList(start, currentEnd + 1);
// Sanity checks
if (potentialMatchFiles.size() < minFiles) {
continue;
}
if (potentialMatchFiles.size() > maxFiles) {
continue;
}
// Compute the total size of files that will
// have to be read if this set of files is compacted.
long size = getTotalStoreSize(potentialMatchFiles);
// Store the smallest set of files. This stored set of files will be used
// if it looks like the algorithm is stuck.
if (mightBeStuck && size < smallestSize) {
smallest = potentialMatchFiles;
smallestSize = size;
}
if (size > comConf.getMaxCompactSize(mayUseOffPeak)) {
continue;
}
++opts;
if (size >= comConf.getMinCompactSize()
&& !filesInRatio(potentialMatchFiles, currentRatio)) {
continue;
}
++optsInRatio;
if (isBetterSelection(bestSelection, bestSize, potentialMatchFiles, size, mightBeStuck)) {
bestSelection = potentialMatchFiles;
bestSize = size;
bestStart = start;
}
}
}
if (bestSelection.size() == 0 && mightBeStuck) {
LOG.debug("Exploring compaction algorithm has selected " + smallest.size()
+ " files of size "+ smallestSize + " because the store might be stuck");
return new ArrayList(smallest);
}
LOG.debug("Exploring compaction algorithm has selected " + bestSelection.size()
+ " files of size " + bestSize + " starting at candidate #" + bestStart +
" after considering " + opts + " permutations with " + optsInRatio + " in ratio");
return new ArrayList(bestSelection);
}
private boolean isBetterSelection(List bestSelection,
long bestSize, List selection, long size, boolean mightBeStuck) {
if (mightBeStuck && bestSize > 0 && size > 0) {
// Keep the selection that removes most files for least size. That penaltizes adding
// large files to compaction, but not small files, so we don't become totally inefficient
// (might want to tweak that in future). Also, given the current order of looking at
// permutations, prefer earlier files and smaller selection if the difference is small.
final double REPLACE_IF_BETTER_BY = 1.05;
double thresholdQuality = ((double)bestSelection.size() / bestSize) * REPLACE_IF_BETTER_BY;
return thresholdQuality < ((double)selection.size() / size);
}
// Keep if this gets rid of more files. Or the same number of files for less io.
return selection.size() > bestSelection.size()
|| (selection.size() == bestSelection.size() && size < bestSize);
}
/**
* Find the total size of a list of store files.
* @param potentialMatchFiles StoreFile list.
* @return Sum of StoreFile.getReader().length();
*/
private long getTotalStoreSize(final List potentialMatchFiles) {
long size = 0;
for (StoreFile s:potentialMatchFiles) {
size += s.getReader().length();
}
return size;
}
/**
* Check that all files satisfy the constraint
* FileSize(i) <= ( Sum(0,N,FileSize(_)) - FileSize(i) ) * Ratio.
*
* @param files List of store files to consider as a compaction candidate.
* @param currentRatio The ratio to use.
* @return a boolean if these files satisfy the ratio constraints.
*/
private boolean filesInRatio(final List files, final double currentRatio) {
if (files.size() < 2) {
return true;
}
long totalFileSize = getTotalStoreSize(files);
for (StoreFile file : files) {
long singleFileSize = file.getReader().length();
long sumAllOtherFileSizes = totalFileSize - singleFileSize;
if (singleFileSize > sumAllOtherFileSizes * currentRatio) {
return false;
}
}
return true;
}
}