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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.db.compaction;
import java.util.*;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Predicate;
import com.google.common.collect.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.cql3.statements.CFPropDefs;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.io.sstable.SSTableReader;
import org.apache.cassandra.utils.Pair;
public class DateTieredCompactionStrategy extends AbstractCompactionStrategy
{
private static final Logger logger = LoggerFactory.getLogger(DateTieredCompactionStrategy.class);
private final DateTieredCompactionStrategyOptions options;
protected volatile int estimatedRemainingTasks;
private final Set sstables = new HashSet<>();
public DateTieredCompactionStrategy(ColumnFamilyStore cfs, Map options)
{
super(cfs, options);
this.estimatedRemainingTasks = 0;
this.options = new DateTieredCompactionStrategyOptions(options);
}
@Override
public synchronized AbstractCompactionTask getNextBackgroundTask(int gcBefore)
{
if (!isEnabled())
return null;
while (true)
{
List latestBucket = getNextBackgroundSStables(gcBefore);
if (latestBucket.isEmpty())
return null;
if (cfs.getDataTracker().markCompacting(latestBucket))
return new CompactionTask(cfs, latestBucket, gcBefore, false);
}
}
/**
*
* @param gcBefore
* @return
*/
private List getNextBackgroundSStables(final int gcBefore)
{
if (!isEnabled() || cfs.getSSTables().isEmpty())
return Collections.emptyList();
int base = cfs.getMinimumCompactionThreshold();
long now = getNow();
Iterable candidates = filterSuspectSSTables(Sets.intersection(cfs.getUncompactingSSTables(), sstables));
List mostInteresting = getCompactionCandidates(candidates, now, base);
if (mostInteresting != null)
{
return mostInteresting;
}
// if there is no sstable to compact in standard way, try compacting single sstable whose droppable tombstone
// ratio is greater than threshold.
List sstablesWithTombstones = Lists.newArrayList();
for (SSTableReader sstable : candidates)
{
if (worthDroppingTombstones(sstable, gcBefore))
sstablesWithTombstones.add(sstable);
}
if (sstablesWithTombstones.isEmpty())
return Collections.emptyList();
return Collections.singletonList(Collections.min(sstablesWithTombstones, new SSTableReader.SizeComparator()));
}
private List getCompactionCandidates(Iterable candidateSSTables, long now, int base)
{
Iterable candidates = filterOldSSTables(Lists.newArrayList(candidateSSTables), options.maxSSTableAge, now);
List> buckets = getBuckets(createSSTableAndMinTimestampPairs(candidates), options.baseTime, base, now);
logger.debug("Compaction buckets are {}", buckets);
updateEstimatedCompactionsByTasks(buckets);
List mostInteresting = newestBucket(buckets, cfs.getMinimumCompactionThreshold(), cfs.getMaximumCompactionThreshold());
if (!mostInteresting.isEmpty())
return mostInteresting;
return null;
}
/**
* Gets the timestamp that DateTieredCompactionStrategy considers to be the "current time".
* @return the maximum timestamp across all SSTables.
* @throws java.util.NoSuchElementException if there are no SSTables.
*/
private long getNow()
{
return Collections.max(cfs.getSSTables(), new Comparator()
{
public int compare(SSTableReader o1, SSTableReader o2)
{
return Long.compare(o1.getMaxTimestamp(), o2.getMaxTimestamp());
}
}).getMaxTimestamp();
}
/**
* Removes all sstables with max timestamp older than maxSSTableAge.
* @param sstables all sstables to consider
* @param maxSSTableAge the age in milliseconds when an SSTable stops participating in compactions
* @param now current time. SSTables with max timestamp less than (now - maxSSTableAge) are filtered.
* @return a list of sstables with the oldest sstables excluded
*/
@VisibleForTesting
static Iterable filterOldSSTables(List sstables, long maxSSTableAge, long now)
{
if (maxSSTableAge == 0)
return sstables;
final long cutoff = now - maxSSTableAge;
return Iterables.filter(sstables, new Predicate()
{
@Override
public boolean apply(SSTableReader sstable)
{
return sstable.getMaxTimestamp() >= cutoff;
}
});
}
/**
*
* @param sstables
* @return
*/
public static List> createSSTableAndMinTimestampPairs(Iterable sstables)
{
List> sstableMinTimestampPairs = Lists.newArrayListWithCapacity(Iterables.size(sstables));
for (SSTableReader sstable : sstables)
sstableMinTimestampPairs.add(Pair.create(sstable, sstable.getMinTimestamp()));
return sstableMinTimestampPairs;
}
@Override
public void addSSTable(SSTableReader sstable)
{
sstables.add(sstable);
}
@Override
public void removeSSTable(SSTableReader sstable)
{
sstables.remove(sstable);
}
/**
* A target time span used for bucketing SSTables based on timestamps.
*/
private static class Target
{
// How big a range of timestamps fit inside the target.
public final long size;
// A timestamp t hits the target iff t / size == divPosition.
public final long divPosition;
public Target(long size, long divPosition)
{
this.size = size;
this.divPosition = divPosition;
}
/**
* Compares the target to a timestamp.
* @param timestamp the timestamp to compare.
* @return a negative integer, zero, or a positive integer as the target lies before, covering, or after than the timestamp.
*/
public int compareToTimestamp(long timestamp)
{
return Long.compare(divPosition, timestamp / size);
}
/**
* Tells if the timestamp hits the target.
* @param timestamp the timestamp to test.
* @return true iff timestamp / size == divPosition.
*/
public boolean onTarget(long timestamp)
{
return compareToTimestamp(timestamp) == 0;
}
/**
* Gets the next target, which represents an earlier time span.
* @param base The number of contiguous targets that will have the same size. Targets following those will be base times as big.
* @return
*/
public Target nextTarget(int base)
{
if (divPosition % base > 0)
return new Target(size, divPosition - 1);
else
return new Target(size * base, divPosition / base - 1);
}
}
/**
* Group files with similar min timestamp into buckets. Files with recent min timestamps are grouped together into
* buckets designated to short timespans while files with older timestamps are grouped into buckets representing
* longer timespans.
* @param files pairs consisting of a file and its min timestamp
* @param timeUnit
* @param base
* @param now
* @return a list of buckets of files. The list is ordered such that the files with newest timestamps come first.
* Each bucket is also a list of files ordered from newest to oldest.
*/
@VisibleForTesting
static List> getBuckets(Collection> files, long timeUnit, int base, long now)
{
// Sort files by age. Newest first.
final List> sortedFiles = Lists.newArrayList(files);
Collections.sort(sortedFiles, Collections.reverseOrder(new Comparator>()
{
public int compare(Pair p1, Pair p2)
{
return p1.right.compareTo(p2.right);
}
}));
List> buckets = Lists.newArrayList();
Target target = getInitialTarget(now, timeUnit);
PeekingIterator> it = Iterators.peekingIterator(sortedFiles.iterator());
outerLoop:
while (it.hasNext())
{
while (!target.onTarget(it.peek().right))
{
// If the file is too new for the target, skip it.
if (target.compareToTimestamp(it.peek().right) < 0)
{
it.next();
if (!it.hasNext())
break outerLoop;
}
else // If the file is too old for the target, switch targets.
target = target.nextTarget(base);
}
List bucket = Lists.newArrayList();
while (target.onTarget(it.peek().right))
{
bucket.add(it.next().left);
if (!it.hasNext())
break;
}
buckets.add(bucket);
}
return buckets;
}
@VisibleForTesting
static Target getInitialTarget(long now, long timeUnit)
{
return new Target(timeUnit, now / timeUnit);
}
private void updateEstimatedCompactionsByTasks(List> tasks)
{
int n = 0;
for (List bucket : tasks)
{
if (bucket.size() >= cfs.getMinimumCompactionThreshold())
n += Math.ceil((double)bucket.size() / cfs.getMaximumCompactionThreshold());
}
estimatedRemainingTasks = n;
}
/**
* @param buckets list of buckets, sorted from newest to oldest, from which to return the newest bucket within thresholds.
* @param minThreshold minimum number of sstables in a bucket to qualify.
* @param maxThreshold maximum number of sstables to compact at once (the returned bucket will be trimmed down to this).
* @return a bucket (list) of sstables to compact.
*/
@VisibleForTesting
static List newestBucket(List> buckets, int minThreshold, int maxThreshold)
{
// Skip buckets containing less than minThreshold sstables, and limit other buckets to maxThreshold sstables.
for (List bucket : buckets)
if (bucket.size() >= minThreshold)
return trimToThreshold(bucket, maxThreshold);
return Collections.emptyList();
}
/**
* @param bucket list of sstables, ordered from newest to oldest by getMinTimestamp().
* @param maxThreshold maximum number of sstables in a single compaction task.
* @return A bucket trimmed to the maxThreshold newest sstables.
*/
@VisibleForTesting
static List trimToThreshold(List bucket, int maxThreshold)
{
// Trim the oldest sstables off the end to meet the maxThreshold
return bucket.subList(0, Math.min(bucket.size(), maxThreshold));
}
@Override
public synchronized Collection getMaximalTask(int gcBefore)
{
Iterable sstables = cfs.markAllCompacting();
if (sstables == null)
return null;
return Arrays.asList(new CompactionTask(cfs, sstables, gcBefore, false));
}
@Override
public synchronized AbstractCompactionTask getUserDefinedTask(Collection sstables, int gcBefore)
{
assert !sstables.isEmpty(); // checked for by CM.submitUserDefined
if (!cfs.getDataTracker().markCompacting(sstables))
{
logger.debug("Unable to mark {} for compaction; probably a background compaction got to it first. You can disable background compactions temporarily if this is a problem", sstables);
return null;
}
return new CompactionTask(cfs, sstables, gcBefore, false).setUserDefined(true);
}
public int getEstimatedRemainingTasks()
{
return estimatedRemainingTasks;
}
public long getMaxSSTableBytes()
{
return Long.MAX_VALUE;
}
public static Map validateOptions(Map options) throws ConfigurationException
{
Map uncheckedOptions = AbstractCompactionStrategy.validateOptions(options);
uncheckedOptions = DateTieredCompactionStrategyOptions.validateOptions(options, uncheckedOptions);
uncheckedOptions.remove(CFPropDefs.KW_MINCOMPACTIONTHRESHOLD);
uncheckedOptions.remove(CFPropDefs.KW_MAXCOMPACTIONTHRESHOLD);
return uncheckedOptions;
}
public String toString()
{
return String.format("DateTieredCompactionStrategy[%s/%s]",
cfs.getMinimumCompactionThreshold(),
cfs.getMaximumCompactionThreshold());
}
}
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