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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.cassandra.db.compaction;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.TreeSet;
import java.util.concurrent.TimeUnit;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.db.lifecycle.SSTableSet;
import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.schema.CompactionParams;
import org.apache.cassandra.utils.Pair;
import static com.google.common.collect.Iterables.filter;
public class TimeWindowCompactionStrategy extends AbstractCompactionStrategy
{
private static final Logger logger = LoggerFactory.getLogger(TimeWindowCompactionStrategy.class);
private final TimeWindowCompactionStrategyOptions options;
protected volatile int estimatedRemainingTasks;
private final Set sstables = new HashSet<>();
private long lastExpiredCheck;
private long highestWindowSeen;
public TimeWindowCompactionStrategy(ColumnFamilyStore cfs, Map options)
{
super(cfs, options);
this.estimatedRemainingTasks = 0;
this.options = new TimeWindowCompactionStrategyOptions(options);
if (!options.containsKey(AbstractCompactionStrategy.TOMBSTONE_COMPACTION_INTERVAL_OPTION) && !options.containsKey(AbstractCompactionStrategy.TOMBSTONE_THRESHOLD_OPTION))
{
disableTombstoneCompactions = true;
logger.debug("Disabling tombstone compactions for TWCS");
}
else
logger.debug("Enabling tombstone compactions for TWCS");
}
@Override
@SuppressWarnings("resource") // transaction is closed by AbstractCompactionTask::execute
public AbstractCompactionTask getNextBackgroundTask(int gcBefore)
{
while (true)
{
List latestBucket = getNextBackgroundSSTables(gcBefore);
if (latestBucket.isEmpty())
return null;
LifecycleTransaction modifier = cfs.getTracker().tryModify(latestBucket, OperationType.COMPACTION);
if (modifier != null)
return new CompactionTask(cfs, modifier, gcBefore);
}
}
/**
*
* @param gcBefore
* @return
*/
private synchronized List getNextBackgroundSSTables(final int gcBefore)
{
if (Iterables.isEmpty(cfs.getSSTables(SSTableSet.LIVE)))
return Collections.emptyList();
Set uncompacting = ImmutableSet.copyOf(filter(cfs.getUncompactingSSTables(), sstables::contains));
// Find fully expired SSTables. Those will be included no matter what.
Set expired = Collections.emptySet();
if (System.currentTimeMillis() - lastExpiredCheck > options.expiredSSTableCheckFrequency)
{
logger.debug("TWCS expired check sufficiently far in the past, checking for fully expired SSTables");
expired = CompactionController.getFullyExpiredSSTables(cfs, uncompacting, cfs.getOverlappingLiveSSTables(uncompacting), gcBefore);
lastExpiredCheck = System.currentTimeMillis();
}
else
{
logger.debug("TWCS skipping check for fully expired SSTables");
}
Set candidates = Sets.newHashSet(filterSuspectSSTables(uncompacting));
List compactionCandidates = new ArrayList<>(getNextNonExpiredSSTables(Sets.difference(candidates, expired), gcBefore));
if (!expired.isEmpty())
{
logger.debug("Including expired sstables: {}", expired);
compactionCandidates.addAll(expired);
}
return compactionCandidates;
}
private List getNextNonExpiredSSTables(Iterable nonExpiringSSTables, final int gcBefore)
{
List mostInteresting = getCompactionCandidates(nonExpiringSSTables);
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 = new ArrayList<>();
for (SSTableReader sstable : nonExpiringSSTables)
{
if (worthDroppingTombstones(sstable, gcBefore))
sstablesWithTombstones.add(sstable);
}
if (sstablesWithTombstones.isEmpty())
return Collections.emptyList();
return Collections.singletonList(Collections.min(sstablesWithTombstones, SSTableReader.sizeComparator));
}
private List getCompactionCandidates(Iterable candidateSSTables)
{
Pair, Long> buckets = getBuckets(candidateSSTables, options.sstableWindowUnit, options.sstableWindowSize, options.timestampResolution);
// Update the highest window seen, if necessary
if(buckets.right > this.highestWindowSeen)
this.highestWindowSeen = buckets.right;
updateEstimatedCompactionsByTasks(buckets.left);
List mostInteresting = newestBucket(buckets.left,
cfs.getMinimumCompactionThreshold(),
cfs.getMaximumCompactionThreshold(),
options.stcsOptions,
this.highestWindowSeen);
if (!mostInteresting.isEmpty())
return mostInteresting;
return null;
}
@Override
public void addSSTable(SSTableReader sstable)
{
sstables.add(sstable);
}
@Override
public void removeSSTable(SSTableReader sstable)
{
sstables.remove(sstable);
}
/**
* Find the lowest and highest timestamps in a given timestamp/unit pair
* Returns milliseconds, caller should adjust accordingly
*/
public static Pair getWindowBoundsInMillis(TimeUnit windowTimeUnit, int windowTimeSize, long timestampInMillis)
{
long lowerTimestamp;
long upperTimestamp;
long timestampInSeconds = TimeUnit.SECONDS.convert(timestampInMillis, TimeUnit.MILLISECONDS);
switch(windowTimeUnit)
{
case MINUTES:
lowerTimestamp = timestampInSeconds - ((timestampInSeconds) % (60L * windowTimeSize));
upperTimestamp = (lowerTimestamp + (60L * (windowTimeSize - 1L))) + 59L;
break;
case HOURS:
lowerTimestamp = timestampInSeconds - ((timestampInSeconds) % (3600L * windowTimeSize));
upperTimestamp = (lowerTimestamp + (3600L * (windowTimeSize - 1L))) + 3599L;
break;
case DAYS:
default:
lowerTimestamp = timestampInSeconds - ((timestampInSeconds) % (86400L * windowTimeSize));
upperTimestamp = (lowerTimestamp + (86400L * (windowTimeSize - 1L))) + 86399L;
break;
}
return Pair.create(TimeUnit.MILLISECONDS.convert(lowerTimestamp, TimeUnit.SECONDS),
TimeUnit.MILLISECONDS.convert(upperTimestamp, TimeUnit.SECONDS));
}
/**
* Group files with similar max timestamp into buckets.
*
* @param files pairs consisting of a file and its min timestamp
* @param sstableWindowUnit
* @param sstableWindowSize
* @param timestampResolution
* @return A pair, where the left element is the bucket representation (map of timestamp to sstablereader), and the right is the highest timestamp seen
*/
@VisibleForTesting
static Pair, Long> getBuckets(Iterable files, TimeUnit sstableWindowUnit, int sstableWindowSize, TimeUnit timestampResolution)
{
HashMultimap buckets = HashMultimap.create();
long maxTimestamp = 0;
// Create hash map to represent buckets
// For each sstable, add sstable to the time bucket
// Where the bucket is the file's max timestamp rounded to the nearest window bucket
for (SSTableReader f : files)
{
assert TimeWindowCompactionStrategyOptions.validTimestampTimeUnits.contains(timestampResolution);
long tStamp = TimeUnit.MILLISECONDS.convert(f.getMaxTimestamp(), timestampResolution);
Pair bounds = getWindowBoundsInMillis(sstableWindowUnit, sstableWindowSize, tStamp);
buckets.put(bounds.left, f);
if (bounds.left > maxTimestamp)
maxTimestamp = bounds.left;
}
logger.trace("buckets {}, max timestamp {}", buckets, maxTimestamp);
return Pair.create(buckets, maxTimestamp);
}
private void updateEstimatedCompactionsByTasks(HashMultimap tasks)
{
int n = 0;
long now = this.highestWindowSeen;
for(Long key : tasks.keySet())
{
// For current window, make sure it's compactable
if (key.compareTo(now) >= 0 && tasks.get(key).size() >= cfs.getMinimumCompactionThreshold())
n++;
else if (key.compareTo(now) < 0 && tasks.get(key).size() >= 2)
n++;
}
this.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(HashMultimap buckets, int minThreshold, int maxThreshold, SizeTieredCompactionStrategyOptions stcsOptions, long now)
{
// If the current bucket has at least minThreshold SSTables, choose that one.
// For any other bucket, at least 2 SSTables is enough.
// In any case, limit to maxThreshold SSTables.
TreeSet allKeys = new TreeSet<>(buckets.keySet());
Iterator it = allKeys.descendingIterator();
while(it.hasNext())
{
Long key = it.next();
Set bucket = buckets.get(key);
logger.trace("Key {}, now {}", key, now);
if (bucket.size() >= minThreshold && key >= now)
{
// If we're in the newest bucket, we'll use STCS to prioritize sstables
List> pairs = SizeTieredCompactionStrategy.createSSTableAndLengthPairs(bucket);
List> stcsBuckets = SizeTieredCompactionStrategy.getBuckets(pairs, stcsOptions.bucketHigh, stcsOptions.bucketLow, stcsOptions.minSSTableSize);
logger.debug("Using STCS compaction for first window of bucket: data files {} , options {}", pairs, stcsOptions);
List stcsInterestingBucket = SizeTieredCompactionStrategy.mostInterestingBucket(stcsBuckets, minThreshold, maxThreshold);
// If the tables in the current bucket aren't eligible in the STCS strategy, we'll skip it and look for other buckets
if (!stcsInterestingBucket.isEmpty())
return stcsInterestingBucket;
}
else if (bucket.size() >= 2 && key < now)
{
logger.debug("bucket size {} >= 2 and not in current bucket, compacting what's here: {}", bucket.size(), bucket);
return trimToThreshold(bucket, maxThreshold);
}
else
{
logger.debug("No compaction necessary for bucket size {} , key {}, now {}", bucket.size(), key, now);
}
}
return Collections.emptyList();
}
/**
* @param bucket set of sstables
* @param maxThreshold maximum number of sstables in a single compaction task.
* @return A bucket trimmed to the maxThreshold newest sstables.
*/
@VisibleForTesting
static List trimToThreshold(Set bucket, int maxThreshold)
{
List ssTableReaders = new ArrayList<>(bucket);
// Trim the largest sstables off the end to meet the maxThreshold
Collections.sort(ssTableReaders, SSTableReader.sizeComparator);
return ImmutableList.copyOf(Iterables.limit(ssTableReaders, maxThreshold));
}
@Override
@SuppressWarnings("resource") // transaction is closed by AbstractCompactionTask::execute
public synchronized Collection getMaximalTask(int gcBefore, boolean splitOutput)
{
Iterable filteredSSTables = filterSuspectSSTables(sstables);
if (Iterables.isEmpty(filteredSSTables))
return null;
LifecycleTransaction txn = cfs.getTracker().tryModify(filteredSSTables, OperationType.COMPACTION);
if (txn == null)
return null;
return Collections.singleton(new CompactionTask(cfs, txn, gcBefore));
}
@Override
@SuppressWarnings("resource") // transaction is closed by AbstractCompactionTask::execute
public synchronized AbstractCompactionTask getUserDefinedTask(Collection sstables, int gcBefore)
{
assert !sstables.isEmpty(); // checked for by CM.submitUserDefined
LifecycleTransaction modifier = cfs.getTracker().tryModify(sstables, OperationType.COMPACTION);
if (modifier == null)
{
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, modifier, gcBefore).setUserDefined(true);
}
public int getEstimatedRemainingTasks()
{
return this.estimatedRemainingTasks;
}
public long getMaxSSTableBytes()
{
return Long.MAX_VALUE;
}
public static Map validateOptions(Map options) throws ConfigurationException
{
Map uncheckedOptions = AbstractCompactionStrategy.validateOptions(options);
uncheckedOptions = TimeWindowCompactionStrategyOptions.validateOptions(options, uncheckedOptions);
uncheckedOptions.remove(CompactionParams.Option.MIN_THRESHOLD.toString());
uncheckedOptions.remove(CompactionParams.Option.MAX_THRESHOLD.toString());
return uncheckedOptions;
}
public String toString()
{
return String.format("TimeWindowCompactionStrategy[%s/%s]",
cfs.getMinimumCompactionThreshold(),
cfs.getMaximumCompactionThreshold());
}
}