src/java/org/apache/cassandra/db/compaction/LeveledGenerations.java - cassandra - Git at Google

 /*
  * 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<SSTableReader, SSTableReader> allSSTables = new HashMap<>();
     private final Set<SSTableReader> l0 = new HashSet<>();
     private static long lastOverlapCheck = System.nanoTime();
     // note that since l0 is broken out, levels[0] represents L1:
     private final TreeSet<SSTableReader> [] levels = new TreeSet[MAX_LEVEL_COUNT - 1];

     private static final Comparator<SSTableReader> 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<SSTableReader> 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<SSTableReader> 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<SSTableReader> 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)
             {
                 if (strictLCSChecksTest) // we can only assert this in tests since this is normal when for example moving sstables from unrepaired to repaired
                     throw new AssertionError("Got unexpected overlap in level "+sstable.getSSTableLevel());
                 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.descriptor.getMetadataSerializer().mutateLevel(sstable.descriptor, 0);
             sstable.reloadSSTableMetadata();
         }
         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<SSTableReader> 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<SSTableReader> allSSTables()
     {
         ImmutableSet.Builder<SSTableReader> builder = ImmutableSet.builder();
         builder.addAll(l0);
         for (Set<SSTableReader> 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<SSTableReader> wrappingIterator(int lvl, SSTableReader lastCompactedSSTable)
     {
         assert lvl > 0; // only makes sense in L1+
         TreeSet<SSTableReader> level = levels[lvl - 1];
         if (level.isEmpty())
             return Collections.emptyIterator();
         if (lastCompactedSSTable == null)
             return level.iterator();

         PeekingIterator<SSTableReader> 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<SSTableReader> level = get(i);
                 if (!level.isEmpty())
                 {
                     logger.trace("L{} contains {} SSTables ({}) in {}",
                                  i,
                                  level.size(),
                                  FBUtilities.prettyPrintMemory(SSTableReader.getTotalBytes(level)),
                                  this);
                 }
             }
         }
     }

     Set<SSTableReader>[] snapshot()
     {
         Set<SSTableReader> [] 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);
                 }
             }
         }
     }
 }
	/*
	* 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<SSTableReader, SSTableReader> allSSTables = new HashMap<>();
	private final Set<SSTableReader> l0 = new HashSet<>();
	private static long lastOverlapCheck = System.nanoTime();
	// note that since l0 is broken out, levels[0] represents L1:
	private final TreeSet<SSTableReader> [] levels = new TreeSet[MAX_LEVEL_COUNT - 1];

	private static final Comparator<SSTableReader> 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<SSTableReader> 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<SSTableReader> 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<SSTableReader> 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)
	{
	if (strictLCSChecksTest) // we can only assert this in tests since this is normal when for example moving sstables from unrepaired to repaired
	throw new AssertionError("Got unexpected overlap in level "+sstable.getSSTableLevel());
	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.descriptor.getMetadataSerializer().mutateLevel(sstable.descriptor, 0);
	sstable.reloadSSTableMetadata();
	}
	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<SSTableReader> 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<SSTableReader> allSSTables()
	{
	ImmutableSet.Builder<SSTableReader> builder = ImmutableSet.builder();
	builder.addAll(l0);
	for (Set<SSTableReader> 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<SSTableReader> wrappingIterator(int lvl, SSTableReader lastCompactedSSTable)
	{
	assert lvl > 0; // only makes sense in L1+
	TreeSet<SSTableReader> level = levels[lvl - 1];
	if (level.isEmpty())
	return Collections.emptyIterator();
	if (lastCompactedSSTable == null)
	return level.iterator();

	PeekingIterator<SSTableReader> 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<SSTableReader> level = get(i);
	if (!level.isEmpty())
	{
	logger.trace("L{} contains {} SSTables ({}) in {}",
	i,
	level.size(),
	FBUtilities.prettyPrintMemory(SSTableReader.getTotalBytes(level)),
	this);
	}
	}
	}
	}

	Set<SSTableReader>[] snapshot()
	{
	Set<SSTableReader> [] 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);
	}
	}
	}
	}
	}