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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.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.TimeUnit;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterators;
import com.google.common.collect.PeekingIterator;
import com.google.common.primitives.Ints;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.utils.FBUtilities;
/**
* Handles the leveled manifest generations
*
* Not thread safe, all access should be synchronized in LeveledManifest
*/
class LeveledGenerations
{
private static final Logger logger = LoggerFactory.getLogger(LeveledGenerations.class);
private final boolean strictLCSChecksTest = Boolean.getBoolean(Config.PROPERTY_PREFIX + "test.strict_lcs_checks");
// It includes L0, i.e. we support [L0 - L8] levels
static final int MAX_LEVEL_COUNT = 9;
/**
* This map is used to track the original NORMAL instances of sstables
*
* When aborting a compaction we can get notified that a MOVED_STARTS sstable is replaced with a NORMAL instance
* of the same sstable but since we use sorted sets (on the first token) in L1+ we won't find it and won't remove it.
* Then, when we add the NORMAL instance we have to replace the *instance* of the sstable to be able to later mark
* it compacting again.
*
* In this map we rely on the fact that hashCode and equals do not care about first token, so when we
* do allSSTables.get(instance_with_moved_starts) we will get the NORMAL sstable back, which we can then remove
* from the TreeSet.
*/
private final Map allSSTables = new HashMap<>();
private final Set l0 = new HashSet<>();
private static long lastOverlapCheck = System.nanoTime();
// note that since l0 is broken out, levels[0] represents L1:
private final TreeSet [] levels = new TreeSet[MAX_LEVEL_COUNT - 1];
private static final Comparator nonL0Comparator = (o1, o2) -> {
int cmp = SSTableReader.sstableComparator.compare(o1, o2);
if (cmp == 0)
cmp = Ints.compare(o1.descriptor.generation, o2.descriptor.generation);
return cmp;
};
LeveledGenerations()
{
for (int i = 0; i < MAX_LEVEL_COUNT - 1; i++)
levels[i] = new TreeSet<>(nonL0Comparator);
}
Set get(int level)
{
if (level > levelCount() - 1 || level < 0)
throw new ArrayIndexOutOfBoundsException("Invalid generation " + level + " - maximum is " + (levelCount() - 1));
if (level == 0)
return l0;
return levels[level - 1];
}
int levelCount()
{
return levels.length + 1;
}
/**
* Adds readers to the correct level
*
* If adding an sstable would cause an overlap in the level (if level > 1) we send it to L0. This can happen
* for example when moving sstables from unrepaired to repaired.
*
* If the sstable is already in the manifest we replace the instance.
*
* If the sstable exists in the manifest but has the wrong level, it is removed from the wrong level and added to the correct one
*
* todo: group sstables per level, add all if level is currently empty, improve startup speed
*/
void addAll(Iterable readers)
{
logDistribution();
for (SSTableReader sstable : readers)
{
assert sstable.getSSTableLevel() < levelCount() : "Invalid level " + sstable.getSSTableLevel() + " out of " + (levelCount() - 1);
int existingLevel = getLevelIfExists(sstable);
if (existingLevel != -1)
{
if (sstable.getSSTableLevel() != existingLevel)
{
logger.error("SSTable {} on the wrong level in the manifest - {} instead of {} as recorded in the sstable metadata, removing from level {}", sstable, existingLevel, sstable.getSSTableLevel(), existingLevel);
if (strictLCSChecksTest)
throw new AssertionError("SSTable not in matching level in manifest: "+sstable + ": "+existingLevel+" != " + sstable.getSSTableLevel());
}
else
{
logger.info("Manifest already contains {} in level {} - replacing instance", sstable, existingLevel);
}
get(existingLevel).remove(sstable);
allSSTables.remove(sstable);
}
allSSTables.put(sstable, sstable);
if (sstable.getSSTableLevel() == 0)
{
l0.add(sstable);
continue;
}
TreeSet level = levels[sstable.getSSTableLevel() - 1];
/*
current level: |-----||----||----| |---||---|
new sstable: |--|
^ before
^ after
overlap if before.last >= newsstable.first or after.first <= newsstable.last
*/
SSTableReader after = level.ceiling(sstable);
SSTableReader before = level.floor(sstable);
if (before != null && before.last.compareTo(sstable.first) >= 0 ||
after != null && after.first.compareTo(sstable.last) <= 0)
{
sendToL0(sstable);
}
else
{
level.add(sstable);
}
}
maybeVerifyLevels();
}
/**
* Sends sstable to L0 by mutating its level in the sstable metadata.
*
* SSTable should not exist in the manifest
*/
private void sendToL0(SSTableReader sstable)
{
try
{
sstable.mutateLevelAndReload(0);
}
catch (IOException e)
{
// Adding it to L0 and marking suspect is probably the best we can do here - it won't create overlap
// and we won't pick it for later compactions.
logger.error("Failed mutating sstable metadata for {} - adding it to L0 to avoid overlap. Marking suspect", sstable, e);
sstable.markSuspect();
}
l0.add(sstable);
}
/**
* Tries to find the sstable in the levels without using the sstable-recorded level
*
* Used to make sure we don't try to re-add an existing sstable
*/
private int getLevelIfExists(SSTableReader sstable)
{
for (int i = 0; i < levelCount(); i++)
{
if (get(i).contains(sstable))
return i;
}
return -1;
}
int remove(Collection readers)
{
int minLevel = Integer.MAX_VALUE;
for (SSTableReader sstable : readers)
{
int level = sstable.getSSTableLevel();
minLevel = Math.min(minLevel, level);
SSTableReader versionInManifest = allSSTables.get(sstable);
if (versionInManifest != null)
{
get(level).remove(versionInManifest);
allSSTables.remove(versionInManifest);
}
}
return minLevel;
}
int[] getAllLevelSize()
{
int[] counts = new int[levelCount()];
for (int i = 0; i < levelCount(); i++)
counts[i] = get(i).size();
return counts;
}
Set allSSTables()
{
ImmutableSet.Builder builder = ImmutableSet.builder();
builder.addAll(l0);
for (Set sstables : levels)
builder.addAll(sstables);
return builder.build();
}
/**
* given a level with sstables with first tokens [0, 10, 20, 30] and a lastCompactedSSTable with last = 15, we will
* return an Iterator over [20, 30, 0, 10].
*/
Iterator wrappingIterator(int lvl, SSTableReader lastCompactedSSTable)
{
assert lvl > 0; // only makes sense in L1+
TreeSet level = levels[lvl - 1];
if (level.isEmpty())
return Collections.emptyIterator();
if (lastCompactedSSTable == null)
return level.iterator();
PeekingIterator tail = Iterators.peekingIterator(level.tailSet(lastCompactedSSTable).iterator());
SSTableReader pivot = null;
// then we need to make sure that the first token of the pivot is greater than the last token of the lastCompactedSSTable
while (tail.hasNext())
{
SSTableReader potentialPivot = tail.peek();
if (potentialPivot.first.compareTo(lastCompactedSSTable.last) > 0)
{
pivot = potentialPivot;
break;
}
tail.next();
}
if (pivot == null)
return level.iterator();
return Iterators.concat(tail, level.headSet(pivot, false).iterator());
}
void logDistribution()
{
if (logger.isTraceEnabled())
{
for (int i = 0; i < levelCount(); i++)
{
Set level = get(i);
if (!level.isEmpty())
{
logger.trace("L{} contains {} SSTables ({}) in {}",
i,
level.size(),
FBUtilities.prettyPrintMemory(SSTableReader.getTotalBytes(level)),
this);
}
}
}
}
Set[] snapshot()
{
Set [] levelsCopy = new Set[levelCount()];
for (int i = 0; i < levelCount(); i++)
levelsCopy[i] = ImmutableSet.copyOf(get(i));
return levelsCopy;
}
/**
* do extra verification of the sstables in the generations
*
* only used during tests
*/
private void maybeVerifyLevels()
{
if (!strictLCSChecksTest || System.nanoTime() - lastOverlapCheck <= TimeUnit.NANOSECONDS.convert(5, TimeUnit.SECONDS))
return;
logger.info("LCS verifying levels");
lastOverlapCheck = System.nanoTime();
for (int i = 1; i < levelCount(); i++)
{
SSTableReader prev = null;
for (SSTableReader sstable : get(i))
{
// no overlap:
assert prev == null || prev.last.compareTo(sstable.first) < 0;
prev = sstable;
// make sure it does not exist in any other level:
for (int j = 0; j < levelCount(); j++)
{
if (i == j)
continue;
assert !get(j).contains(sstable);
}
}
}
}
void newLevel(SSTableReader sstable, int oldLevel)
{
SSTableReader versionInManifest = allSSTables.remove(sstable);
boolean removed = false;
if (versionInManifest != null)
removed = get(oldLevel).remove(versionInManifest);
if (!removed)
logger.warn("Could not remove "+sstable+" from "+oldLevel);
addAll(Collections.singleton(sstable));
}
}