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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.

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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.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.BooleanSupplier;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import javax.management.openmbean.OpenDataException;
import javax.management.openmbean.TabularData;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Collections2;
import com.google.common.collect.ConcurrentHashMultiset;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multiset;
import com.google.common.collect.Sets;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListenableFutureTask;
import com.google.common.util.concurrent.RateLimiter;
import com.google.common.util.concurrent.Uninterruptibles;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import io.netty.util.concurrent.FastThreadLocal;
import org.apache.cassandra.cache.AutoSavingCache;
import org.apache.cassandra.concurrent.DebuggableThreadPoolExecutor;
import org.apache.cassandra.concurrent.JMXEnabledThreadPoolExecutor;
import org.apache.cassandra.concurrent.NamedThreadFactory;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.db.Directories;
import org.apache.cassandra.db.DiskBoundaries;
import org.apache.cassandra.db.Keyspace;
import org.apache.cassandra.db.SerializationHeader;
import org.apache.cassandra.db.SystemKeyspace;
import org.apache.cassandra.db.compaction.CompactionInfo.Holder;
import org.apache.cassandra.db.lifecycle.ILifecycleTransaction;
import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
import org.apache.cassandra.db.lifecycle.SSTableIntervalTree;
import org.apache.cassandra.db.lifecycle.SSTableSet;
import org.apache.cassandra.db.lifecycle.View;
import org.apache.cassandra.db.lifecycle.WrappedLifecycleTransaction;
import org.apache.cassandra.db.rows.UnfilteredRowIterator;
import org.apache.cassandra.db.view.ViewBuilderTask;
import org.apache.cassandra.dht.AbstractBounds;
import org.apache.cassandra.dht.Bounds;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.dht.Token;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.index.SecondaryIndexBuilder;
import org.apache.cassandra.io.sstable.Descriptor;
import org.apache.cassandra.io.sstable.ISSTableScanner;
import org.apache.cassandra.io.sstable.IndexSummaryRedistribution;
import org.apache.cassandra.io.sstable.SSTableRewriter;
import org.apache.cassandra.io.sstable.SnapshotDeletingTask;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.io.sstable.format.SSTableWriter;
import org.apache.cassandra.io.sstable.metadata.MetadataCollector;
import org.apache.cassandra.io.sstable.metadata.StatsMetadata;
import org.apache.cassandra.io.util.FileUtils;
import org.apache.cassandra.locator.RangesAtEndpoint;
import org.apache.cassandra.metrics.CompactionMetrics;
import org.apache.cassandra.metrics.TableMetrics;
import org.apache.cassandra.schema.CompactionParams.TombstoneOption;
import org.apache.cassandra.schema.Schema;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.service.ActiveRepairService;
import org.apache.cassandra.service.StorageService;
import org.apache.cassandra.streaming.PreviewKind;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.JVMStabilityInspector;
import org.apache.cassandra.utils.MBeanWrapper;
import org.apache.cassandra.utils.Throwables;
import org.apache.cassandra.utils.UUIDGen;
import org.apache.cassandra.utils.WrappedRunnable;
import org.apache.cassandra.utils.concurrent.Refs;

import static java.util.Collections.singleton;
import static org.apache.cassandra.service.ActiveRepairService.NO_PENDING_REPAIR;
import static org.apache.cassandra.service.ActiveRepairService.UNREPAIRED_SSTABLE;

/**
 * 

* A singleton which manages a private executor of ongoing compactions. *

* Scheduling for compaction is accomplished by swapping sstables to be compacted into * a set via Tracker. New scheduling attempts will ignore currently compacting * sstables. */ public class CompactionManager implements CompactionManagerMBean { public static final String MBEAN_OBJECT_NAME = "org.apache.cassandra.db:type=CompactionManager"; private static final Logger logger = LoggerFactory.getLogger(CompactionManager.class); public static final CompactionManager instance; @VisibleForTesting public final AtomicInteger currentlyBackgroundUpgrading = new AtomicInteger(0); public static final int NO_GC = Integer.MIN_VALUE; public static final int GC_ALL = Integer.MAX_VALUE; // A thread local that tells us if the current thread is owned by the compaction manager. Used // by CounterContext to figure out if it should log a warning for invalid counter shards. public static final FastThreadLocal isCompactionManager = new FastThreadLocal() { @Override protected Boolean initialValue() { return false; } }; static { instance = new CompactionManager(); MBeanWrapper.instance.registerMBean(instance, MBEAN_OBJECT_NAME); } private final CompactionExecutor executor = new CompactionExecutor(); private final ValidationExecutor validationExecutor = new ValidationExecutor(); private final CompactionExecutor cacheCleanupExecutor = new CacheCleanupExecutor(); private final CompactionExecutor viewBuildExecutor = new ViewBuildExecutor(); private final CompactionMetrics metrics = new CompactionMetrics(executor, validationExecutor, viewBuildExecutor); @VisibleForTesting final Multiset compactingCF = ConcurrentHashMultiset.create(); public final ActiveCompactions active = new ActiveCompactions(); // used to temporarily pause non-strategy managed compactions (like index summary redistribution) private final AtomicInteger globalCompactionPauseCount = new AtomicInteger(0); private final RateLimiter compactionRateLimiter = RateLimiter.create(Double.MAX_VALUE); public CompactionMetrics getMetrics() { return metrics; } /** * Gets compaction rate limiter. * Rate unit is bytes per sec. * * @return RateLimiter with rate limit set */ public RateLimiter getRateLimiter() { setRate(DatabaseDescriptor.getCompactionThroughputMbPerSec()); return compactionRateLimiter; } /** * Sets the rate for the rate limiter. When compaction_throughput_mb_per_sec is 0 or node is bootstrapping, * this sets the rate to Double.MAX_VALUE bytes per second. * @param throughPutMbPerSec throughput to set in mb per second */ public void setRate(final double throughPutMbPerSec) { double throughput = throughPutMbPerSec * 1024.0 * 1024.0; // if throughput is set to 0, throttling is disabled if (throughput == 0 || StorageService.instance.isBootstrapMode()) throughput = Double.MAX_VALUE; if (compactionRateLimiter.getRate() != throughput) compactionRateLimiter.setRate(throughput); } /** * Call this whenever a compaction might be needed on the given columnfamily. * It's okay to over-call (within reason) if a call is unnecessary, it will * turn into a no-op in the bucketing/candidate-scan phase. */ public List> submitBackground(final ColumnFamilyStore cfs) { if (cfs.isAutoCompactionDisabled()) { logger.trace("Autocompaction is disabled"); return Collections.emptyList(); } /** * If a CF is currently being compacted, and there are no idle threads, submitBackground should be a no-op; * we can wait for the current compaction to finish and re-submit when more information is available. * Otherwise, we should submit at least one task to prevent starvation by busier CFs, and more if there * are idle threads stil. (CASSANDRA-4310) */ int count = compactingCF.count(cfs); if (count > 0 && executor.getActiveCount() >= executor.getMaximumPoolSize()) { logger.trace("Background compaction is still running for {}.{} ({} remaining). Skipping", cfs.keyspace.getName(), cfs.name, count); return Collections.emptyList(); } logger.trace("Scheduling a background task check for {}.{} with {}", cfs.keyspace.getName(), cfs.name, cfs.getCompactionStrategyManager().getName()); List> futures = new ArrayList<>(1); Future fut = executor.submitIfRunning(new BackgroundCompactionCandidate(cfs), "background task"); if (!fut.isCancelled()) futures.add(fut); else compactingCF.remove(cfs); return futures; } public boolean isCompacting(Iterable cfses, Predicate sstablePredicate) { for (ColumnFamilyStore cfs : cfses) if (cfs.getTracker().getCompacting().stream().anyMatch(sstablePredicate)) return true; return false; } @VisibleForTesting public boolean hasOngoingOrPendingTasks() { if (!active.getCompactions().isEmpty() || !compactingCF.isEmpty()) return true; int pendingTasks = executor.getPendingTaskCount() + validationExecutor.getPendingTaskCount() + viewBuildExecutor.getPendingTaskCount() + cacheCleanupExecutor.getPendingTaskCount(); if (pendingTasks > 0) return true; int activeTasks = executor.getActiveTaskCount() + validationExecutor.getActiveTaskCount() + viewBuildExecutor.getActiveTaskCount() + cacheCleanupExecutor.getActiveTaskCount(); return activeTasks > 0; } /** * Shutdowns both compaction and validation executors, cancels running compaction / validation, * and waits for tasks to complete if tasks were not cancelable. */ public void forceShutdown() { // shutdown executors to prevent further submission executor.shutdown(); validationExecutor.shutdown(); viewBuildExecutor.shutdown(); cacheCleanupExecutor.shutdown(); // interrupt compactions and validations for (Holder compactionHolder : active.getCompactions()) { compactionHolder.stop(); } // wait for tasks to terminate // compaction tasks are interrupted above, so it shuold be fairy quick // until not interrupted tasks to complete. for (ExecutorService exec : Arrays.asList(executor, validationExecutor, viewBuildExecutor, cacheCleanupExecutor)) { try { if (!exec.awaitTermination(1, TimeUnit.MINUTES)) logger.warn("Failed to wait for compaction executors shutdown"); } catch (InterruptedException e) { logger.error("Interrupted while waiting for tasks to be terminated", e); } } } public void finishCompactionsAndShutdown(long timeout, TimeUnit unit) throws InterruptedException { executor.shutdown(); executor.awaitTermination(timeout, unit); } // the actual sstables to compact are not determined until we run the BCT; that way, if new sstables // are created between task submission and execution, we execute against the most up-to-date information @VisibleForTesting class BackgroundCompactionCandidate implements Runnable { private final ColumnFamilyStore cfs; BackgroundCompactionCandidate(ColumnFamilyStore cfs) { compactingCF.add(cfs); this.cfs = cfs; } public void run() { boolean ranCompaction = false; try { logger.trace("Checking {}.{}", cfs.keyspace.getName(), cfs.name); if (!cfs.isValid()) { logger.trace("Aborting compaction for dropped CF"); return; } CompactionStrategyManager strategy = cfs.getCompactionStrategyManager(); AbstractCompactionTask task = strategy.getNextBackgroundTask(getDefaultGcBefore(cfs, FBUtilities.nowInSeconds())); if (task == null) { if (DatabaseDescriptor.automaticSSTableUpgrade()) ranCompaction = maybeRunUpgradeTask(strategy); } else { task.execute(active); ranCompaction = true; } } finally { compactingCF.remove(cfs); } if (ranCompaction) // only submit background if we actually ran a compaction - otherwise we end up in an infinite loop submitting noop background tasks submitBackground(cfs); } boolean maybeRunUpgradeTask(CompactionStrategyManager strategy) { logger.debug("Checking for upgrade tasks {}.{}", cfs.keyspace.getName(), cfs.getTableName()); try { if (currentlyBackgroundUpgrading.incrementAndGet() <= DatabaseDescriptor.maxConcurrentAutoUpgradeTasks()) { AbstractCompactionTask upgradeTask = strategy.findUpgradeSSTableTask(); if (upgradeTask != null) { upgradeTask.execute(active); return true; } } } finally { currentlyBackgroundUpgrading.decrementAndGet(); } logger.trace("No tasks available"); return false; } } @VisibleForTesting public BackgroundCompactionCandidate getBackgroundCompactionCandidate(ColumnFamilyStore cfs) { return new BackgroundCompactionCandidate(cfs); } /** * Run an operation over all sstables using jobs threads * * @param cfs the column family store to run the operation on * @param operation the operation to run * @param jobs the number of threads to use - 0 means use all available. It never uses more than concurrent_compactors threads * @return status of the operation * @throws ExecutionException * @throws InterruptedException */ @SuppressWarnings("resource") private AllSSTableOpStatus parallelAllSSTableOperation(final ColumnFamilyStore cfs, final OneSSTableOperation operation, int jobs, OperationType operationType) throws ExecutionException, InterruptedException { logger.info("Starting {} for {}.{}", operationType, cfs.keyspace.getName(), cfs.getTableName()); List transactions = new ArrayList<>(); List> futures = new ArrayList<>(); try (LifecycleTransaction compacting = cfs.markAllCompacting(operationType)) { if (compacting == null) return AllSSTableOpStatus.UNABLE_TO_CANCEL; Iterable sstables = Lists.newArrayList(operation.filterSSTables(compacting)); if (Iterables.isEmpty(sstables)) { logger.info("No sstables to {} for {}.{}", operationType.name(), cfs.keyspace.getName(), cfs.name); return AllSSTableOpStatus.SUCCESSFUL; } for (final SSTableReader sstable : sstables) { final LifecycleTransaction txn = compacting.split(singleton(sstable)); transactions.add(txn); Callable callable = new Callable() { @Override public Object call() throws Exception { operation.execute(txn); return this; } }; Future fut = executor.submitIfRunning(callable, "paralell sstable operation"); if (!fut.isCancelled()) futures.add(fut); else return AllSSTableOpStatus.ABORTED; if (jobs > 0 && futures.size() == jobs) { Future f = FBUtilities.waitOnFirstFuture(futures); futures.remove(f); } } FBUtilities.waitOnFutures(futures); assert compacting.originals().isEmpty(); logger.info("Finished {} for {}.{} successfully", operationType, cfs.keyspace.getName(), cfs.getTableName()); return AllSSTableOpStatus.SUCCESSFUL; } finally { // wait on any unfinished futures to make sure we don't close an ongoing transaction try { FBUtilities.waitOnFutures(futures); } catch (Throwable t) { // these are handled/logged in CompactionExecutor#afterExecute } Throwable fail = Throwables.close(null, transactions); if (fail != null) logger.error("Failed to cleanup lifecycle transactions ({} for {}.{})", operationType, cfs.keyspace.getName(), cfs.getTableName(), fail); } } private static interface OneSSTableOperation { Iterable filterSSTables(LifecycleTransaction transaction); void execute(LifecycleTransaction input) throws IOException; } public enum AllSSTableOpStatus { SUCCESSFUL(0), ABORTED(1), UNABLE_TO_CANCEL(2); public final int statusCode; AllSSTableOpStatus(int statusCode) { this.statusCode = statusCode; } } public AllSSTableOpStatus performScrub(final ColumnFamilyStore cfs, final boolean skipCorrupted, final boolean checkData, int jobs) throws InterruptedException, ExecutionException { return performScrub(cfs, skipCorrupted, checkData, false, jobs); } public AllSSTableOpStatus performScrub(final ColumnFamilyStore cfs, final boolean skipCorrupted, final boolean checkData, final boolean reinsertOverflowedTTL, int jobs) throws InterruptedException, ExecutionException { return parallelAllSSTableOperation(cfs, new OneSSTableOperation() { @Override public Iterable filterSSTables(LifecycleTransaction input) { return input.originals(); } @Override public void execute(LifecycleTransaction input) { scrubOne(cfs, input, skipCorrupted, checkData, reinsertOverflowedTTL, active); } }, jobs, OperationType.SCRUB); } public AllSSTableOpStatus performVerify(ColumnFamilyStore cfs, Verifier.Options options) throws InterruptedException, ExecutionException { assert !cfs.isIndex(); return parallelAllSSTableOperation(cfs, new OneSSTableOperation() { @Override public Iterable filterSSTables(LifecycleTransaction input) { return input.originals(); } @Override public void execute(LifecycleTransaction input) { verifyOne(cfs, input.onlyOne(), options, active); } }, 0, OperationType.VERIFY); } public AllSSTableOpStatus performSSTableRewrite(final ColumnFamilyStore cfs, final boolean excludeCurrentVersion, int jobs) throws InterruptedException, ExecutionException { return parallelAllSSTableOperation(cfs, new OneSSTableOperation() { @Override public Iterable filterSSTables(LifecycleTransaction transaction) { List sortedSSTables = Lists.newArrayList(transaction.originals()); Collections.sort(sortedSSTables, SSTableReader.sizeComparator.reversed()); Iterator iter = sortedSSTables.iterator(); while (iter.hasNext()) { SSTableReader sstable = iter.next(); if (excludeCurrentVersion && sstable.descriptor.version.equals(sstable.descriptor.getFormat().getLatestVersion())) { transaction.cancel(sstable); iter.remove(); } } return sortedSSTables; } @Override public void execute(LifecycleTransaction txn) { AbstractCompactionTask task = cfs.getCompactionStrategyManager().getCompactionTask(txn, NO_GC, Long.MAX_VALUE); task.setUserDefined(true); task.setCompactionType(OperationType.UPGRADE_SSTABLES); task.execute(active); } }, jobs, OperationType.UPGRADE_SSTABLES); } public AllSSTableOpStatus performCleanup(final ColumnFamilyStore cfStore, int jobs) throws InterruptedException, ExecutionException { assert !cfStore.isIndex(); Keyspace keyspace = cfStore.keyspace; if (!StorageService.instance.getTokenMetadata().getPendingRanges(keyspace.getName(), FBUtilities.getBroadcastAddressAndPort()).isEmpty()) { logger.info("Cleanup cannot run while node has pending ranges for keyspace {} table {}, wait for node addition/decommission to complete and try again", cfStore.keyspace.getName(), cfStore.getTableName()); return AllSSTableOpStatus.ABORTED; } // if local ranges is empty, it means no data should remain final RangesAtEndpoint replicas = StorageService.instance.getLocalReplicas(keyspace.getName()); final Set> allRanges = replicas.ranges(); final Set> transientRanges = replicas.onlyTransient().ranges(); final Set> fullRanges = replicas.onlyFull().ranges(); final boolean hasIndexes = cfStore.indexManager.hasIndexes(); return parallelAllSSTableOperation(cfStore, new OneSSTableOperation() { @Override public Iterable filterSSTables(LifecycleTransaction transaction) { List sortedSSTables = Lists.newArrayList(transaction.originals()); Iterator sstableIter = sortedSSTables.iterator(); int totalSSTables = 0; int skippedSStables = 0; while (sstableIter.hasNext()) { SSTableReader sstable = sstableIter.next(); boolean needsCleanupFull = needsCleanup(sstable, fullRanges); boolean needsCleanupTransient = !transientRanges.isEmpty() && sstable.isRepaired() && needsCleanup(sstable, transientRanges); //If there are no ranges for which the table needs cleanup either due to lack of intersection or lack //of the table being repaired. totalSSTables++; if (!needsCleanupFull && !needsCleanupTransient) { logger.debug("Skipping {} ([{}, {}]) for cleanup; all rows should be kept. Needs cleanup full ranges: {} Needs cleanup transient ranges: {} Repaired: {}", sstable, sstable.first.getToken(), sstable.last.getToken(), needsCleanupFull, needsCleanupTransient, sstable.isRepaired()); sstableIter.remove(); transaction.cancel(sstable); skippedSStables++; } } logger.info("Skipping cleanup for {}/{} sstables for {}.{} since they are fully contained in owned ranges (full ranges: {}, transient ranges: {})", skippedSStables, totalSSTables, cfStore.keyspace.getName(), cfStore.getTableName(), fullRanges, transientRanges); sortedSSTables.sort(SSTableReader.sizeComparator); return sortedSSTables; } @Override public void execute(LifecycleTransaction txn) throws IOException { CleanupStrategy cleanupStrategy = CleanupStrategy.get(cfStore, allRanges, transientRanges, txn.onlyOne().isRepaired(), FBUtilities.nowInSeconds()); doCleanupOne(cfStore, txn, cleanupStrategy, replicas.ranges(), hasIndexes); } }, jobs, OperationType.CLEANUP); } public AllSSTableOpStatus performGarbageCollection(final ColumnFamilyStore cfStore, TombstoneOption tombstoneOption, int jobs) throws InterruptedException, ExecutionException { assert !cfStore.isIndex(); return parallelAllSSTableOperation(cfStore, new OneSSTableOperation() { @Override public Iterable filterSSTables(LifecycleTransaction transaction) { List filteredSSTables = new ArrayList<>(); if (cfStore.getCompactionStrategyManager().onlyPurgeRepairedTombstones()) { for (SSTableReader sstable : transaction.originals()) { if (!sstable.isRepaired()) { try { transaction.cancel(sstable); } catch (Throwable t) { logger.warn(String.format("Unable to cancel %s from transaction %s", sstable, transaction.opId()), t); } } else { filteredSSTables.add(sstable); } } } else { filteredSSTables.addAll(transaction.originals()); } filteredSSTables.sort(SSTableReader.maxTimestampAscending); return filteredSSTables; } @Override public void execute(LifecycleTransaction txn) throws IOException { logger.debug("Garbage collecting {}", txn.originals()); CompactionTask task = new CompactionTask(cfStore, txn, getDefaultGcBefore(cfStore, FBUtilities.nowInSeconds())) { @Override protected CompactionController getCompactionController(Set toCompact) { return new CompactionController(cfStore, toCompact, gcBefore, null, tombstoneOption); } @Override protected int getLevel() { return txn.onlyOne().getSSTableLevel(); } }; task.setUserDefined(true); task.setCompactionType(OperationType.GARBAGE_COLLECT); task.execute(active); } }, jobs, OperationType.GARBAGE_COLLECT); } public AllSSTableOpStatus relocateSSTables(final ColumnFamilyStore cfs, int jobs) throws ExecutionException, InterruptedException { if (!cfs.getPartitioner().splitter().isPresent()) { logger.info("Partitioner does not support splitting"); return AllSSTableOpStatus.ABORTED; } if (StorageService.instance.getLocalReplicas(cfs.keyspace.getName()).isEmpty()) { logger.info("Relocate cannot run before a node has joined the ring"); return AllSSTableOpStatus.ABORTED; } final DiskBoundaries diskBoundaries = cfs.getDiskBoundaries(); return parallelAllSSTableOperation(cfs, new OneSSTableOperation() { @Override public Iterable filterSSTables(LifecycleTransaction transaction) { Set originals = Sets.newHashSet(transaction.originals()); Set needsRelocation = originals.stream().filter(s -> !inCorrectLocation(s)).collect(Collectors.toSet()); transaction.cancel(Sets.difference(originals, needsRelocation)); Map> groupedByDisk = groupByDiskIndex(needsRelocation); int maxSize = 0; for (List diskSSTables : groupedByDisk.values()) maxSize = Math.max(maxSize, diskSSTables.size()); List mixedSSTables = new ArrayList<>(); for (int i = 0; i < maxSize; i++) for (List diskSSTables : groupedByDisk.values()) if (i < diskSSTables.size()) mixedSSTables.add(diskSSTables.get(i)); return mixedSSTables; } public Map> groupByDiskIndex(Set needsRelocation) { return needsRelocation.stream().collect(Collectors.groupingBy((s) -> diskBoundaries.getDiskIndex(s))); } private boolean inCorrectLocation(SSTableReader sstable) { if (!cfs.getPartitioner().splitter().isPresent()) return true; // Compare the expected data directory for the sstable with its current data directory Directories.DataDirectory currentDirectory = cfs.getDirectories().getDataDirectoryForFile(sstable.descriptor); return diskBoundaries.isInCorrectLocation(sstable, currentDirectory); } @Override public void execute(LifecycleTransaction txn) { logger.debug("Relocating {}", txn.originals()); AbstractCompactionTask task = cfs.getCompactionStrategyManager().getCompactionTask(txn, NO_GC, Long.MAX_VALUE); task.setUserDefined(true); task.setCompactionType(OperationType.RELOCATE); task.execute(active); } }, jobs, OperationType.RELOCATE); } /** * Splits the given token ranges of the given sstables into a pending repair silo */ public ListenableFuture submitPendingAntiCompaction(ColumnFamilyStore cfs, RangesAtEndpoint tokenRanges, Refs sstables, LifecycleTransaction txn, UUID sessionId, BooleanSupplier isCancelled) { Runnable runnable = new WrappedRunnable() { protected void runMayThrow() throws Exception { try (TableMetrics.TableTimer.Context ctx = cfs.metric.anticompactionTime.time()) { performAnticompaction(cfs, tokenRanges, sstables, txn, sessionId, isCancelled); } } }; ListenableFuture task = null; try { task = executor.submitIfRunning(runnable, "pending anticompaction"); return task; } finally { if (task == null || task.isCancelled()) { sstables.release(); txn.abort(); } } } /** * for sstables that are fully contained in the given ranges, just rewrite their metadata with * the pending repair id and remove them from the transaction */ private static void mutateFullyContainedSSTables(ColumnFamilyStore cfs, Refs refs, Iterator sstableIterator, Collection> ranges, LifecycleTransaction txn, UUID sessionID, boolean isTransient) throws IOException { if (ranges.isEmpty()) return; List> normalizedRanges = Range.normalize(ranges); Set fullyContainedSSTables = findSSTablesToAnticompact(sstableIterator, normalizedRanges, sessionID); cfs.metric.bytesMutatedAnticompaction.inc(SSTableReader.getTotalBytes(fullyContainedSSTables)); cfs.getCompactionStrategyManager().mutateRepaired(fullyContainedSSTables, UNREPAIRED_SSTABLE, sessionID, isTransient); // since we're just re-writing the sstable metdata for the fully contained sstables, we don't want // them obsoleted when the anti-compaction is complete. So they're removed from the transaction here txn.cancel(fullyContainedSSTables); refs.release(fullyContainedSSTables); } /** * Make sure the {validatedForRepair} are marked for compaction before calling this. * * Caller must reference the validatedForRepair sstables (via ParentRepairSession.getActiveRepairedSSTableRefs(..)). * * @param cfs * @param replicas token ranges to be repaired * @param validatedForRepair SSTables containing the repaired ranges. Should be referenced before passing them. * @param sessionID the repair session we're anti-compacting for * @param isCancelled function that indicates if active anti-compaction should be canceled * @throws InterruptedException * @throws IOException */ public void performAnticompaction(ColumnFamilyStore cfs, RangesAtEndpoint replicas, Refs validatedForRepair, LifecycleTransaction txn, UUID sessionID, BooleanSupplier isCancelled) throws IOException { try { ActiveRepairService.ParentRepairSession prs = ActiveRepairService.instance.getParentRepairSession(sessionID); Preconditions.checkArgument(!prs.isPreview(), "Cannot anticompact for previews"); Preconditions.checkArgument(!replicas.isEmpty(), "No ranges to anti-compact"); if (logger.isInfoEnabled()) logger.info("{} Starting anticompaction for {}.{} on {}/{} sstables", PreviewKind.NONE.logPrefix(sessionID), cfs.keyspace.getName(), cfs.getTableName(), validatedForRepair.size(), cfs.getLiveSSTables().size()); if (logger.isTraceEnabled()) logger.trace("{} Starting anticompaction for ranges {}", PreviewKind.NONE.logPrefix(sessionID), replicas); Set sstables = new HashSet<>(validatedForRepair); validateSSTableBoundsForAnticompaction(sessionID, sstables, replicas); mutateFullyContainedSSTables(cfs, validatedForRepair, sstables.iterator(), replicas.onlyFull().ranges(), txn, sessionID, false); mutateFullyContainedSSTables(cfs, validatedForRepair, sstables.iterator(), replicas.onlyTransient().ranges(), txn, sessionID, true); assert txn.originals().equals(sstables); if (!sstables.isEmpty()) doAntiCompaction(cfs, replicas, txn, sessionID, isCancelled); txn.finish(); } finally { validatedForRepair.release(); txn.close(); } logger.info("{} Completed anticompaction successfully", PreviewKind.NONE.logPrefix(sessionID)); } static void validateSSTableBoundsForAnticompaction(UUID sessionID, Collection sstables, RangesAtEndpoint ranges) { List> normalizedRanges = Range.normalize(ranges.ranges()); for (SSTableReader sstable : sstables) { Bounds bounds = new Bounds<>(sstable.first.getToken(), sstable.last.getToken()); if (!Iterables.any(normalizedRanges, r -> (r.contains(bounds.left) && r.contains(bounds.right)) || r.intersects(bounds))) { // this should never happen - in PendingAntiCompaction#getSSTables we select all sstables that intersect the repaired ranges, that can't have changed here String message = String.format("%s SSTable %s (%s) does not intersect repaired ranges %s, this sstable should not have been included.", PreviewKind.NONE.logPrefix(sessionID), sstable, bounds, normalizedRanges); logger.error(message); throw new IllegalStateException(message); } } } @VisibleForTesting static Set findSSTablesToAnticompact(Iterator sstableIterator, List> normalizedRanges, UUID parentRepairSession) { Set fullyContainedSSTables = new HashSet<>(); while (sstableIterator.hasNext()) { SSTableReader sstable = sstableIterator.next(); Bounds sstableBounds = new Bounds<>(sstable.first.getToken(), sstable.last.getToken()); for (Range r : normalizedRanges) { // ranges are normalized - no wrap around - if first and last are contained we know that all tokens are contained in the range if (r.contains(sstable.first.getToken()) && r.contains(sstable.last.getToken())) { logger.info("{} SSTable {} fully contained in range {}, mutating repairedAt instead of anticompacting", PreviewKind.NONE.logPrefix(parentRepairSession), sstable, r); fullyContainedSSTables.add(sstable); sstableIterator.remove(); break; } else if (r.intersects(sstableBounds)) { logger.info("{} SSTable {} ({}) will be anticompacted on range {}", PreviewKind.NONE.logPrefix(parentRepairSession), sstable, sstableBounds, r); } } } return fullyContainedSSTables; } public void performMaximal(final ColumnFamilyStore cfStore, boolean splitOutput) { FBUtilities.waitOnFutures(submitMaximal(cfStore, getDefaultGcBefore(cfStore, FBUtilities.nowInSeconds()), splitOutput)); } @SuppressWarnings("resource") // the tasks are executed in parallel on the executor, making sure that they get closed public List> submitMaximal(final ColumnFamilyStore cfStore, final int gcBefore, boolean splitOutput) { // here we compute the task off the compaction executor, so having that present doesn't // confuse runWithCompactionsDisabled -- i.e., we don't want to deadlock ourselves, waiting // for ourselves to finish/acknowledge cancellation before continuing. CompactionTasks tasks = cfStore.getCompactionStrategyManager().getMaximalTasks(gcBefore, splitOutput); if (tasks.isEmpty()) return Collections.emptyList(); List> futures = new ArrayList<>(); int nonEmptyTasks = 0; for (final AbstractCompactionTask task : tasks) { if (task.transaction.originals().size() > 0) nonEmptyTasks++; Runnable runnable = new WrappedRunnable() { protected void runMayThrow() { task.execute(active); } }; Future fut = executor.submitIfRunning(runnable, "maximal task"); if (!fut.isCancelled()) futures.add(fut); } if (nonEmptyTasks > 1) logger.info("Major compaction will not result in a single sstable - repaired and unrepaired data is kept separate and compaction runs per data_file_directory."); return futures; } /** * Forces a major compaction of specified token ranges of the specified column family. *

* The token ranges will be interpreted as closed intervals to match the closed interval defined by the first and * last keys of a sstable, even though the {@link Range} class is suppossed to be half-open by definition. * * @param cfStore The column family store to be compacted. * @param ranges The token ranges to be compacted, interpreted as closed intervals. */ public void forceCompactionForTokenRange(ColumnFamilyStore cfStore, Collection> ranges) { Callable taskCreator = () -> { Collection sstables = sstablesInBounds(cfStore, ranges); if (sstables == null || sstables.isEmpty()) { logger.debug("No sstables found for the provided token range"); return CompactionTasks.empty(); } return cfStore.getCompactionStrategyManager().getUserDefinedTasks(sstables, getDefaultGcBefore(cfStore, FBUtilities.nowInSeconds())); }; try (CompactionTasks tasks = cfStore.runWithCompactionsDisabled(taskCreator, (sstable) -> new Bounds<>(sstable.first.getToken(), sstable.last.getToken()).intersects(ranges), false, false, false)) { if (tasks.isEmpty()) return; Runnable runnable = new WrappedRunnable() { protected void runMayThrow() { for (AbstractCompactionTask task : tasks) if (task != null) task.execute(active); } }; FBUtilities.waitOnFuture(executor.submitIfRunning(runnable, "force compaction for token range")); } } /** * Returns the sstables of the specified column family store that intersect with the specified token ranges. *

* The token ranges will be interpreted as closed intervals to match the closed interval defined by the first and * last keys of a sstable, even though the {@link Range} class is suppossed to be half-open by definition. */ private static Collection sstablesInBounds(ColumnFamilyStore cfs, Collection> tokenRangeCollection) { final Set sstables = new HashSet<>(); Iterable liveTables = cfs.getTracker().getView().select(SSTableSet.LIVE); SSTableIntervalTree tree = SSTableIntervalTree.build(liveTables); for (Range tokenRange : tokenRangeCollection) { if (!AbstractBounds.strictlyWrapsAround(tokenRange.left, tokenRange.right)) { Iterable ssTableReaders = View.sstablesInBounds(tokenRange.left.minKeyBound(), tokenRange.right.maxKeyBound(), tree); Iterables.addAll(sstables, ssTableReaders); } else { // Searching an interval tree will not return the correct results for a wrapping range // so we have to unwrap it first for (Range unwrappedRange : tokenRange.unwrap()) { Iterable ssTableReaders = View.sstablesInBounds(unwrappedRange.left.minKeyBound(), unwrappedRange.right.maxKeyBound(), tree); Iterables.addAll(sstables, ssTableReaders); } } } return sstables; } public void forceUserDefinedCompaction(String dataFiles) { String[] filenames = dataFiles.split(","); Multimap descriptors = ArrayListMultimap.create(); for (String filename : filenames) { // extract keyspace and columnfamily name from filename Descriptor desc = Descriptor.fromFilename(filename.trim()); if (Schema.instance.getTableMetadataRef(desc) == null) { logger.warn("Schema does not exist for file {}. Skipping.", filename); continue; } // group by keyspace/columnfamily ColumnFamilyStore cfs = Keyspace.open(desc.ksname).getColumnFamilyStore(desc.cfname); descriptors.put(cfs, cfs.getDirectories().find(new File(filename.trim()).getName())); } List> futures = new ArrayList<>(descriptors.size()); int nowInSec = FBUtilities.nowInSeconds(); for (ColumnFamilyStore cfs : descriptors.keySet()) futures.add(submitUserDefined(cfs, descriptors.get(cfs), getDefaultGcBefore(cfs, nowInSec))); FBUtilities.waitOnFutures(futures); } public void forceUserDefinedCleanup(String dataFiles) { String[] filenames = dataFiles.split(","); HashMap descriptors = Maps.newHashMap(); for (String filename : filenames) { // extract keyspace and columnfamily name from filename Descriptor desc = Descriptor.fromFilename(filename.trim()); if (Schema.instance.getTableMetadataRef(desc) == null) { logger.warn("Schema does not exist for file {}. Skipping.", filename); continue; } // group by keyspace/columnfamily ColumnFamilyStore cfs = Keyspace.open(desc.ksname).getColumnFamilyStore(desc.cfname); desc = cfs.getDirectories().find(new File(filename.trim()).getName()); if (desc != null) descriptors.put(cfs, desc); } if (!StorageService.instance.isJoined()) { logger.error("Cleanup cannot run before a node has joined the ring"); return; } for (Map.Entry entry : descriptors.entrySet()) { ColumnFamilyStore cfs = entry.getKey(); Keyspace keyspace = cfs.keyspace; final RangesAtEndpoint replicas = StorageService.instance.getLocalReplicas(keyspace.getName()); final Set> allRanges = replicas.ranges(); final Set> transientRanges = replicas.onlyTransient().ranges(); boolean hasIndexes = cfs.indexManager.hasIndexes(); SSTableReader sstable = lookupSSTable(cfs, entry.getValue()); if (sstable == null) { logger.warn("Will not clean {}, it is not an active sstable", entry.getValue()); } else { CleanupStrategy cleanupStrategy = CleanupStrategy.get(cfs, allRanges, transientRanges, sstable.isRepaired(), FBUtilities.nowInSeconds()); try (LifecycleTransaction txn = cfs.getTracker().tryModify(sstable, OperationType.CLEANUP)) { doCleanupOne(cfs, txn, cleanupStrategy, allRanges, hasIndexes); } catch (IOException e) { logger.error("forceUserDefinedCleanup failed: {}", e.getLocalizedMessage()); } } } } public Future submitUserDefined(final ColumnFamilyStore cfs, final Collection dataFiles, final int gcBefore) { Runnable runnable = new WrappedRunnable() { protected void runMayThrow() throws Exception { // look up the sstables now that we're on the compaction executor, so we don't try to re-compact // something that was already being compacted earlier. Collection sstables = new ArrayList<>(dataFiles.size()); for (Descriptor desc : dataFiles) { // inefficient but not in a performance sensitive path SSTableReader sstable = lookupSSTable(cfs, desc); if (sstable == null) { logger.info("Will not compact {}: it is not an active sstable", desc); } else { sstables.add(sstable); } } if (sstables.isEmpty()) { logger.info("No files to compact for user defined compaction"); } else { try (CompactionTasks tasks = cfs.getCompactionStrategyManager().getUserDefinedTasks(sstables, gcBefore)) { for (AbstractCompactionTask task : tasks) { if (task != null) task.execute(active); } } } } }; return executor.submitIfRunning(runnable, "user defined task"); } // This acquire a reference on the sstable // This is not efficient, do not use in any critical path private SSTableReader lookupSSTable(final ColumnFamilyStore cfs, Descriptor descriptor) { for (SSTableReader sstable : cfs.getSSTables(SSTableSet.CANONICAL)) { if (sstable.descriptor.equals(descriptor)) return sstable; } return null; } public Future submitValidation(Callable validation) { return validationExecutor.submitIfRunning(validation, "validation"); } /* Used in tests. */ public void disableAutoCompaction() { for (String ksname : Schema.instance.getNonSystemKeyspaces()) { for (ColumnFamilyStore cfs : Keyspace.open(ksname).getColumnFamilyStores()) cfs.disableAutoCompaction(); } } @VisibleForTesting void scrubOne(ColumnFamilyStore cfs, LifecycleTransaction modifier, boolean skipCorrupted, boolean checkData, boolean reinsertOverflowedTTL, ActiveCompactionsTracker activeCompactions) { CompactionInfo.Holder scrubInfo = null; try (Scrubber scrubber = new Scrubber(cfs, modifier, skipCorrupted, checkData, reinsertOverflowedTTL)) { scrubInfo = scrubber.getScrubInfo(); activeCompactions.beginCompaction(scrubInfo); scrubber.scrub(); } finally { if (scrubInfo != null) activeCompactions.finishCompaction(scrubInfo); } } @VisibleForTesting void verifyOne(ColumnFamilyStore cfs, SSTableReader sstable, Verifier.Options options, ActiveCompactionsTracker activeCompactions) { CompactionInfo.Holder verifyInfo = null; try (Verifier verifier = new Verifier(cfs, sstable, false, options)) { verifyInfo = verifier.getVerifyInfo(); activeCompactions.beginCompaction(verifyInfo); verifier.verify(); } finally { if (verifyInfo != null) activeCompactions.finishCompaction(verifyInfo); } } /** * Determines if a cleanup would actually remove any data in this SSTable based * on a set of owned ranges. */ @VisibleForTesting public static boolean needsCleanup(SSTableReader sstable, Collection> ownedRanges) { if (ownedRanges.isEmpty()) { return true; // all data will be cleaned } // unwrap and sort the ranges by LHS token List> sortedRanges = Range.normalize(ownedRanges); // see if there are any keys LTE the token for the start of the first range // (token range ownership is exclusive on the LHS.) Range firstRange = sortedRanges.get(0); if (sstable.first.getToken().compareTo(firstRange.left) <= 0) return true; // then, iterate over all owned ranges and see if the next key beyond the end of the owned // range falls before the start of the next range for (int i = 0; i < sortedRanges.size(); i++) { Range range = sortedRanges.get(i); if (range.right.isMinimum()) { // we split a wrapping range and this is the second half. // there can't be any keys beyond this (and this is the last range) return false; } DecoratedKey firstBeyondRange = sstable.firstKeyBeyond(range.right.maxKeyBound()); if (firstBeyondRange == null) { // we ran off the end of the sstable looking for the next key; we don't need to check any more ranges return false; } if (i == (sortedRanges.size() - 1)) { // we're at the last range and we found a key beyond the end of the range return true; } Range nextRange = sortedRanges.get(i + 1); if (firstBeyondRange.getToken().compareTo(nextRange.left) <= 0) { // we found a key in between the owned ranges return true; } } return false; } /** * This function goes over a file and removes the keys that the node is not responsible for * and only keeps keys that this node is responsible for. * * @throws IOException */ private void doCleanupOne(final ColumnFamilyStore cfs, LifecycleTransaction txn, CleanupStrategy cleanupStrategy, Collection> allRanges, boolean hasIndexes) throws IOException { assert !cfs.isIndex(); SSTableReader sstable = txn.onlyOne(); // if ranges is empty and no index, entire sstable is discarded if (!hasIndexes && !new Bounds<>(sstable.first.getToken(), sstable.last.getToken()).intersects(allRanges)) { txn.obsoleteOriginals(); txn.finish(); logger.info("SSTable {} ([{}, {}]) does not intersect the owned ranges ({}), dropping it", sstable, sstable.first.getToken(), sstable.last.getToken(), allRanges); return; } long start = System.nanoTime(); long totalkeysWritten = 0; long expectedBloomFilterSize = Math.max(cfs.metadata().params.minIndexInterval, SSTableReader.getApproximateKeyCount(txn.originals())); if (logger.isTraceEnabled()) logger.trace("Expected bloom filter size : {}", expectedBloomFilterSize); logger.info("Cleaning up {}", sstable); File compactionFileLocation = sstable.descriptor.directory; RateLimiter limiter = getRateLimiter(); double compressionRatio = sstable.getCompressionRatio(); if (compressionRatio == MetadataCollector.NO_COMPRESSION_RATIO) compressionRatio = 1.0; List finished; int nowInSec = FBUtilities.nowInSeconds(); try (SSTableRewriter writer = SSTableRewriter.construct(cfs, txn, false, sstable.maxDataAge); ISSTableScanner scanner = cleanupStrategy.getScanner(sstable); CompactionController controller = new CompactionController(cfs, txn.originals(), getDefaultGcBefore(cfs, nowInSec)); Refs refs = Refs.ref(Collections.singleton(sstable)); CompactionIterator ci = new CompactionIterator(OperationType.CLEANUP, Collections.singletonList(scanner), controller, nowInSec, UUIDGen.getTimeUUID(), active)) { StatsMetadata metadata = sstable.getSSTableMetadata(); writer.switchWriter(createWriter(cfs, compactionFileLocation, expectedBloomFilterSize, metadata.repairedAt, metadata.pendingRepair, metadata.isTransient, sstable, txn)); long lastBytesScanned = 0; while (ci.hasNext()) { try (UnfilteredRowIterator partition = ci.next(); UnfilteredRowIterator notCleaned = cleanupStrategy.cleanup(partition)) { if (notCleaned == null) continue; if (writer.append(notCleaned) != null) totalkeysWritten++; long bytesScanned = scanner.getBytesScanned(); compactionRateLimiterAcquire(limiter, bytesScanned, lastBytesScanned, compressionRatio); lastBytesScanned = bytesScanned; } } // flush to ensure we don't lose the tombstones on a restart, since they are not commitlog'd cfs.indexManager.flushAllIndexesBlocking(); finished = writer.finish(); } if (!finished.isEmpty()) { String format = "Cleaned up to %s. %s to %s (~%d%% of original) for %,d keys. Time: %,dms."; long dTime = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start); long startsize = sstable.onDiskLength(); long endsize = 0; for (SSTableReader newSstable : finished) endsize += newSstable.onDiskLength(); double ratio = (double) endsize / (double) startsize; logger.info(String.format(format, finished.get(0).getFilename(), FBUtilities.prettyPrintMemory(startsize), FBUtilities.prettyPrintMemory(endsize), (int) (ratio * 100), totalkeysWritten, dTime)); } } static void compactionRateLimiterAcquire(RateLimiter limiter, long bytesScanned, long lastBytesScanned, double compressionRatio) { long lengthRead = (long) ((bytesScanned - lastBytesScanned) * compressionRatio) + 1; while (lengthRead >= Integer.MAX_VALUE) { limiter.acquire(Integer.MAX_VALUE); lengthRead -= Integer.MAX_VALUE; } if (lengthRead > 0) { limiter.acquire((int) lengthRead); } } private static abstract class CleanupStrategy { protected final Collection> ranges; protected final int nowInSec; protected CleanupStrategy(Collection> ranges, int nowInSec) { this.ranges = ranges; this.nowInSec = nowInSec; } public static CleanupStrategy get(ColumnFamilyStore cfs, Collection> ranges, Collection> transientRanges, boolean isRepaired, int nowInSec) { if (cfs.indexManager.hasIndexes()) { if (!transientRanges.isEmpty()) { //Shouldn't have been possible to create this situation throw new AssertionError("Can't have indexes and transient ranges"); } return new Full(cfs, ranges, nowInSec); } return new Bounded(cfs, ranges, transientRanges, isRepaired, nowInSec); } public abstract ISSTableScanner getScanner(SSTableReader sstable); public abstract UnfilteredRowIterator cleanup(UnfilteredRowIterator partition); private static final class Bounded extends CleanupStrategy { private final Collection> transientRanges; private final boolean isRepaired; public Bounded(final ColumnFamilyStore cfs, Collection> ranges, Collection> transientRanges, boolean isRepaired, int nowInSec) { super(ranges, nowInSec); instance.cacheCleanupExecutor.submit(new Runnable() { @Override public void run() { cfs.cleanupCache(); } }); this.transientRanges = transientRanges; this.isRepaired = isRepaired; } @Override public ISSTableScanner getScanner(SSTableReader sstable) { //If transient replication is enabled and there are transient ranges //then cleanup should remove any partitions that are repaired and in the transient range //as they should already be synchronized at other full replicas. //So just don't scan the portion of the table containing the repaired transient ranges Collection> rangesToScan = ranges; if (isRepaired) { rangesToScan = Collections2.filter(ranges, range -> !transientRanges.contains(range)); } return sstable.getScanner(rangesToScan); } @Override public UnfilteredRowIterator cleanup(UnfilteredRowIterator partition) { return partition; } } private static final class Full extends CleanupStrategy { private final ColumnFamilyStore cfs; public Full(ColumnFamilyStore cfs, Collection> ranges, int nowInSec) { super(ranges, nowInSec); this.cfs = cfs; } @Override public ISSTableScanner getScanner(SSTableReader sstable) { return sstable.getScanner(); } @Override public UnfilteredRowIterator cleanup(UnfilteredRowIterator partition) { if (Range.isInRanges(partition.partitionKey().getToken(), ranges)) return partition; cfs.invalidateCachedPartition(partition.partitionKey()); cfs.indexManager.deletePartition(partition, nowInSec); return null; } } } public static SSTableWriter createWriter(ColumnFamilyStore cfs, File compactionFileLocation, long expectedBloomFilterSize, long repairedAt, UUID pendingRepair, boolean isTransient, SSTableReader sstable, LifecycleTransaction txn) { FileUtils.createDirectory(compactionFileLocation); return SSTableWriter.create(cfs.metadata, cfs.newSSTableDescriptor(compactionFileLocation), expectedBloomFilterSize, repairedAt, pendingRepair, isTransient, sstable.getSSTableLevel(), sstable.header, cfs.indexManager.listIndexes(), txn); } public static SSTableWriter createWriterForAntiCompaction(ColumnFamilyStore cfs, File compactionFileLocation, int expectedBloomFilterSize, long repairedAt, UUID pendingRepair, boolean isTransient, Collection sstables, ILifecycleTransaction txn) { FileUtils.createDirectory(compactionFileLocation); int minLevel = Integer.MAX_VALUE; // if all sstables have the same level, we can compact them together without creating overlap during anticompaction // note that we only anticompact from unrepaired sstables, which is not leveled, but we still keep original level // after first migration to be able to drop the sstables back in their original place in the repaired sstable manifest for (SSTableReader sstable : sstables) { if (minLevel == Integer.MAX_VALUE) minLevel = sstable.getSSTableLevel(); if (minLevel != sstable.getSSTableLevel()) { minLevel = 0; break; } } return SSTableWriter.create(cfs.newSSTableDescriptor(compactionFileLocation), (long) expectedBloomFilterSize, repairedAt, pendingRepair, isTransient, cfs.metadata, new MetadataCollector(sstables, cfs.metadata().comparator, minLevel), SerializationHeader.make(cfs.metadata(), sstables), cfs.indexManager.listIndexes(), txn); } /** * Splits up an sstable into two new sstables. The first of the new tables will store repaired ranges, the second * will store the non-repaired ranges. Once anticompation is completed, the original sstable is marked as compacted * and subsequently deleted. * @param cfs * @param txn a transaction over the repaired sstables to anticompact * @param ranges full and transient ranges to be placed into one of the new sstables. The repaired table will be tracked via * the {@link org.apache.cassandra.io.sstable.metadata.StatsMetadata#pendingRepair} field. * @param pendingRepair the repair session we're anti-compacting for * @param isCancelled function that indicates if active anti-compaction should be canceled */ private void doAntiCompaction(ColumnFamilyStore cfs, RangesAtEndpoint ranges, LifecycleTransaction txn, UUID pendingRepair, BooleanSupplier isCancelled) { int originalCount = txn.originals().size(); logger.info("Performing anticompaction on {} sstables for {}", originalCount, pendingRepair); //Group SSTables Set sstables = txn.originals(); // Repairs can take place on both unrepaired (incremental + full) and repaired (full) data. // Although anti-compaction could work on repaired sstables as well and would result in having more accurate // repairedAt values for these, we still avoid anti-compacting already repaired sstables, as we currently don't // make use of any actual repairedAt value and splitting up sstables just for that is not worth it at this point. Set unrepairedSSTables = sstables.stream().filter((s) -> !s.isRepaired()).collect(Collectors.toSet()); cfs.metric.bytesAnticompacted.inc(SSTableReader.getTotalBytes(unrepairedSSTables)); Collection> groupedSSTables = cfs.getCompactionStrategyManager().groupSSTablesForAntiCompaction(unrepairedSSTables); // iterate over sstables to check if the full / transient / unrepaired ranges intersect them. int antiCompactedSSTableCount = 0; for (Collection sstableGroup : groupedSSTables) { try (LifecycleTransaction groupTxn = txn.split(sstableGroup)) { int antiCompacted = antiCompactGroup(cfs, ranges, groupTxn, pendingRepair, isCancelled); antiCompactedSSTableCount += antiCompacted; } } String format = "Anticompaction completed successfully, anticompacted from {} to {} sstable(s) for {}."; logger.info(format, originalCount, antiCompactedSSTableCount, pendingRepair); } @VisibleForTesting int antiCompactGroup(ColumnFamilyStore cfs, RangesAtEndpoint ranges, LifecycleTransaction txn, UUID pendingRepair, BooleanSupplier isCancelled) { Preconditions.checkArgument(!ranges.isEmpty(), "need at least one full or transient range"); long groupMaxDataAge = -1; for (Iterator i = txn.originals().iterator(); i.hasNext();) { SSTableReader sstable = i.next(); if (groupMaxDataAge < sstable.maxDataAge) groupMaxDataAge = sstable.maxDataAge; } if (txn.originals().size() == 0) { logger.info("No valid anticompactions for this group, All sstables were compacted and are no longer available"); return 0; } logger.info("Anticompacting {} in {}.{} for {}", txn.originals(), cfs.keyspace.getName(), cfs.getTableName(), pendingRepair); Set sstableAsSet = txn.originals(); File destination = cfs.getDirectories().getWriteableLocationAsFile(cfs.getExpectedCompactedFileSize(sstableAsSet, OperationType.ANTICOMPACTION)); int nowInSec = FBUtilities.nowInSeconds(); RateLimiter limiter = getRateLimiter(); /** * HACK WARNING * * We have multiple writers operating over the same Transaction, producing different sets of sstables that all * logically replace the transaction's originals. The SSTableRewriter assumes it has exclusive control over * the transaction state, and this will lead to temporarily inconsistent sstable/tracker state if we do not * take special measures to avoid it. * * Specifically, if a number of rewriter have prepareToCommit() invoked in sequence, then two problematic things happen: * 1. The obsoleteOriginals() call of the first rewriter immediately remove the originals from the tracker, despite * their having been only partially replaced. To avoid this, we must either avoid obsoleteOriginals() or checkpoint() * 2. The LifecycleTransaction may only have prepareToCommit() invoked once, and this will checkpoint() also. * * Similarly commit() would finalise partially complete on-disk state. * * To avoid these problems, we introduce a SharedTxn that proxies all calls onto the underlying transaction * except prepareToCommit(), checkpoint(), obsoleteOriginals(), and commit(). * We then invoke these methods directly once each of the rewriter has updated the transaction * with their share of replacements. * * Note that for the same essential reason we also explicitly disable early open. * By noop-ing checkpoint we avoid any of the problems with early open, but by continuing to explicitly * disable it we also prevent any of the extra associated work from being performed. */ class SharedTxn extends WrappedLifecycleTransaction { public SharedTxn(ILifecycleTransaction delegate) { super(delegate); } public Throwable commit(Throwable accumulate) { return accumulate; } public void prepareToCommit() {} public void checkpoint() {} public void obsoleteOriginals() {} public void close() {} } CompactionStrategyManager strategy = cfs.getCompactionStrategyManager(); try (SharedTxn sharedTxn = new SharedTxn(txn); SSTableRewriter fullWriter = SSTableRewriter.constructWithoutEarlyOpening(sharedTxn, false, groupMaxDataAge); SSTableRewriter transWriter = SSTableRewriter.constructWithoutEarlyOpening(sharedTxn, false, groupMaxDataAge); SSTableRewriter unrepairedWriter = SSTableRewriter.constructWithoutEarlyOpening(sharedTxn, false, groupMaxDataAge); AbstractCompactionStrategy.ScannerList scanners = strategy.getScanners(txn.originals()); CompactionController controller = new CompactionController(cfs, sstableAsSet, getDefaultGcBefore(cfs, nowInSec)); CompactionIterator ci = getAntiCompactionIterator(scanners.scanners, controller, nowInSec, UUIDGen.getTimeUUID(), active, isCancelled)) { int expectedBloomFilterSize = Math.max(cfs.metadata().params.minIndexInterval, (int)(SSTableReader.getApproximateKeyCount(sstableAsSet))); fullWriter.switchWriter(CompactionManager.createWriterForAntiCompaction(cfs, destination, expectedBloomFilterSize, UNREPAIRED_SSTABLE, pendingRepair, false, sstableAsSet, txn)); transWriter.switchWriter(CompactionManager.createWriterForAntiCompaction(cfs, destination, expectedBloomFilterSize, UNREPAIRED_SSTABLE, pendingRepair, true, sstableAsSet, txn)); unrepairedWriter.switchWriter(CompactionManager.createWriterForAntiCompaction(cfs, destination, expectedBloomFilterSize, UNREPAIRED_SSTABLE, NO_PENDING_REPAIR, false, sstableAsSet, txn)); Predicate fullChecker = !ranges.onlyFull().isEmpty() ? new Range.OrderedRangeContainmentChecker(ranges.onlyFull().ranges()) : t -> false; Predicate transChecker = !ranges.onlyTransient().isEmpty() ? new Range.OrderedRangeContainmentChecker(ranges.onlyTransient().ranges()) : t -> false; double compressionRatio = scanners.getCompressionRatio(); if (compressionRatio == MetadataCollector.NO_COMPRESSION_RATIO) compressionRatio = 1.0; long lastBytesScanned = 0; while (ci.hasNext()) { try (UnfilteredRowIterator partition = ci.next()) { Token token = partition.partitionKey().getToken(); // if this row is contained in the full or transient ranges, append it to the appropriate sstable if (fullChecker.test(token)) { fullWriter.append(partition); } else if (transChecker.test(token)) { transWriter.append(partition); } else { // otherwise, append it to the unrepaired sstable unrepairedWriter.append(partition); } long bytesScanned = scanners.getTotalBytesScanned(); compactionRateLimiterAcquire(limiter, bytesScanned, lastBytesScanned, compressionRatio); lastBytesScanned = bytesScanned; } } fullWriter.prepareToCommit(); transWriter.prepareToCommit(); unrepairedWriter.prepareToCommit(); txn.checkpoint(); txn.obsoleteOriginals(); txn.prepareToCommit(); List fullSSTables = new ArrayList<>(fullWriter.finished()); List transSSTables = new ArrayList<>(transWriter.finished()); List unrepairedSSTables = new ArrayList<>(unrepairedWriter.finished()); fullWriter.commit(); transWriter.commit(); unrepairedWriter.commit(); txn.commit(); logger.info("Anticompacted {} in {}.{} to full = {}, transient = {}, unrepaired = {} for {}", sstableAsSet, cfs.keyspace.getName(), cfs.getTableName(), fullSSTables, transSSTables, unrepairedSSTables, pendingRepair); return fullSSTables.size() + transSSTables.size() + unrepairedSSTables.size(); } catch (Throwable e) { if (e instanceof CompactionInterruptedException && isCancelled.getAsBoolean()) { logger.info("Anticompaction has been canceled for session {}", pendingRepair); logger.trace(e.getMessage(), e); } else { JVMStabilityInspector.inspectThrowable(e); logger.error("Error anticompacting " + txn + " for " + pendingRepair, e); } throw e; } } @VisibleForTesting public static CompactionIterator getAntiCompactionIterator(List scanners, CompactionController controller, int nowInSec, UUID timeUUID, ActiveCompactionsTracker activeCompactions, BooleanSupplier isCancelled) { return new CompactionIterator(OperationType.ANTICOMPACTION, scanners, controller, nowInSec, timeUUID, activeCompactions) { public boolean isStopRequested() { return super.isStopRequested() || isCancelled.getAsBoolean(); } }; } @VisibleForTesting ListenableFuture submitIndexBuild(final SecondaryIndexBuilder builder, ActiveCompactionsTracker activeCompactions) { Runnable runnable = new Runnable() { public void run() { activeCompactions.beginCompaction(builder); try { builder.build(); } finally { activeCompactions.finishCompaction(builder); } } }; return executor.submitIfRunning(runnable, "index build"); } /** * Is not scheduled, because it is performing disjoint work from sstable compaction. */ public ListenableFuture submitIndexBuild(final SecondaryIndexBuilder builder) { return submitIndexBuild(builder, active); } public Future submitCacheWrite(final AutoSavingCache.Writer writer) { return submitCacheWrite(writer, active); } Future submitCacheWrite(final AutoSavingCache.Writer writer, ActiveCompactionsTracker activeCompactions) { Runnable runnable = new Runnable() { public void run() { if (!AutoSavingCache.flushInProgress.add(writer.cacheType())) { logger.trace("Cache flushing was already in progress: skipping {}", writer.getCompactionInfo()); return; } try { activeCompactions.beginCompaction(writer); try { writer.saveCache(); } finally { activeCompactions.finishCompaction(writer); } } finally { AutoSavingCache.flushInProgress.remove(writer.cacheType()); } } }; return executor.submitIfRunning(runnable, "cache write"); } public List runIndexSummaryRedistribution(IndexSummaryRedistribution redistribution) throws IOException { return runIndexSummaryRedistribution(redistribution, active); } @VisibleForTesting List runIndexSummaryRedistribution(IndexSummaryRedistribution redistribution, ActiveCompactionsTracker activeCompactions) throws IOException { activeCompactions.beginCompaction(redistribution); try { return redistribution.redistributeSummaries(); } finally { activeCompactions.finishCompaction(redistribution); } } public static int getDefaultGcBefore(ColumnFamilyStore cfs, int nowInSec) { // 2ndary indexes have ExpiringColumns too, so we need to purge tombstones deleted before now. We do not need to // add any GcGrace however since 2ndary indexes are local to a node. return cfs.isIndex() ? nowInSec : cfs.gcBefore(nowInSec); } public ListenableFuture submitViewBuilder(final ViewBuilderTask task) { return submitViewBuilder(task, active); } @VisibleForTesting ListenableFuture submitViewBuilder(final ViewBuilderTask task, ActiveCompactionsTracker activeCompactions) { return viewBuildExecutor.submitIfRunning(() -> { activeCompactions.beginCompaction(task); try { return task.call(); } finally { activeCompactions.finishCompaction(task); } }, "view build"); } public int getActiveCompactions() { return active.getCompactions().size(); } static class CompactionExecutor extends JMXEnabledThreadPoolExecutor { protected CompactionExecutor(int minThreads, int maxThreads, String name, BlockingQueue queue) { super(minThreads, maxThreads, 60, TimeUnit.SECONDS, queue, new NamedThreadFactory(name, Thread.MIN_PRIORITY), "internal"); } private CompactionExecutor(int threadCount, String name) { this(threadCount, threadCount, name, new LinkedBlockingQueue()); } public CompactionExecutor() { this(Math.max(1, DatabaseDescriptor.getConcurrentCompactors()), "CompactionExecutor"); } protected void beforeExecute(Thread t, Runnable r) { // can't set this in Thread factory, so we do it redundantly here isCompactionManager.set(true); super.beforeExecute(t, r); } // modified from DebuggableThreadPoolExecutor so that CompactionInterruptedExceptions are not logged @Override public void afterExecute(Runnable r, Throwable t) { DebuggableThreadPoolExecutor.maybeResetLocalSessionWrapper(r); if (t == null) t = DebuggableThreadPoolExecutor.extractThrowable(r); if (t != null) { if (t instanceof CompactionInterruptedException) { logger.info(t.getMessage()); if (t.getSuppressed() != null && t.getSuppressed().length > 0) logger.warn("Interruption of compaction encountered exceptions:", t); else logger.trace("Full interruption stack trace:", t); } else { DebuggableThreadPoolExecutor.handleOrLog(t); } } // Snapshots cannot be deleted on Windows while segments of the root element are mapped in NTFS. Compactions // unmap those segments which could free up a snapshot for successful deletion. SnapshotDeletingTask.rescheduleFailedTasks(); } public ListenableFuture submitIfRunning(Runnable task, String name) { return submitIfRunning(Executors.callable(task, null), name); } /** * Submit the task but only if the executor has not been shutdown.If the executor has * been shutdown, or in case of a rejected execution exception return a cancelled future. * * @param task - the task to submit * @param name - the task name to use in log messages * * @return the future that will deliver the task result, or a future that has already been * cancelled if the task could not be submitted. */ public ListenableFuture submitIfRunning(Callable task, String name) { if (isShutdown()) { logger.info("Executor has been shut down, not submitting {}", name); return Futures.immediateCancelledFuture(); } try { ListenableFutureTask ret = ListenableFutureTask.create(task); execute(ret); return ret; } catch (RejectedExecutionException ex) { if (isShutdown()) logger.info("Executor has shut down, could not submit {}", name); else logger.error("Failed to submit {}", name, ex); return Futures.immediateCancelledFuture(); } } } // TODO: pull out relevant parts of CompactionExecutor and move to ValidationManager public static class ValidationExecutor extends CompactionExecutor { // CompactionExecutor, and by extension ValidationExecutor, use DebuggableThreadPoolExecutor's // default RejectedExecutionHandler which blocks the submitting thread when the work queue is // full. The calling thread in this case is AntiEntropyStage, so in most cases we don't actually // want to block when the ValidationExecutor is saturated as this prevents progress on all // repair tasks and may cause repair sessions to time out. Also, it can lead to references to // heavyweight validation responses containing merkle trees being held for extended periods which // increases GC pressure. Using LinkedBlockingQueue instead of the default SynchronousQueue allows // tasks to be submitted without blocking the caller, but will always prefer queueing to creating // new threads if the pool already has at least `corePoolSize` threads already running. For this // reason we set corePoolSize to the maximum desired concurrency, but allow idle core threads to // be terminated. public ValidationExecutor() { super(DatabaseDescriptor.getConcurrentValidations(), DatabaseDescriptor.getConcurrentValidations(), "ValidationExecutor", new LinkedBlockingQueue()); allowCoreThreadTimeOut(true); } public void adjustPoolSize() { setMaximumPoolSize(DatabaseDescriptor.getConcurrentValidations()); setCorePoolSize(DatabaseDescriptor.getConcurrentValidations()); } } private static class ViewBuildExecutor extends CompactionExecutor { public ViewBuildExecutor() { super(DatabaseDescriptor.getConcurrentViewBuilders(), "ViewBuildExecutor"); } } private static class CacheCleanupExecutor extends CompactionExecutor { public CacheCleanupExecutor() { super(1, "CacheCleanupExecutor"); } } public void incrementAborted() { metrics.compactionsAborted.inc(); } public void incrementCompactionsReduced() { metrics.compactionsReduced.inc(); } public void incrementSstablesDropppedFromCompactions(long num) { metrics.sstablesDropppedFromCompactions.inc(num); } public List> getCompactions() { List compactionHolders = active.getCompactions(); List> out = new ArrayList>(compactionHolders.size()); for (CompactionInfo.Holder ci : compactionHolders) out.add(ci.getCompactionInfo().asMap()); return out; } public List getCompactionSummary() { List compactionHolders = active.getCompactions(); List out = new ArrayList(compactionHolders.size()); for (CompactionInfo.Holder ci : compactionHolders) out.add(ci.getCompactionInfo().toString()); return out; } public TabularData getCompactionHistory() { try { return SystemKeyspace.getCompactionHistory(); } catch (OpenDataException e) { throw new RuntimeException(e); } } public long getTotalBytesCompacted() { return metrics.bytesCompacted.getCount(); } public long getTotalCompactionsCompleted() { return metrics.totalCompactionsCompleted.getCount(); } public int getPendingTasks() { return metrics.pendingTasks.getValue(); } public long getCompletedTasks() { return metrics.completedTasks.getValue(); } public void stopCompaction(String type) { OperationType operation = OperationType.valueOf(type); for (Holder holder : active.getCompactions()) { if (holder.getCompactionInfo().getTaskType() == operation) holder.stop(); } } public void stopCompactionById(String compactionId) { for (Holder holder : active.getCompactions()) { UUID holderId = holder.getCompactionInfo().getTaskId(); if (holderId != null && holderId.equals(UUID.fromString(compactionId))) holder.stop(); } } public void setConcurrentCompactors(int value) { if (value > executor.getCorePoolSize()) { // we are increasing the value executor.setMaximumPoolSize(value); executor.setCorePoolSize(value); } else if (value < executor.getCorePoolSize()) { // we are reducing the value executor.setCorePoolSize(value); executor.setMaximumPoolSize(value); } } public void setConcurrentValidations() { validationExecutor.adjustPoolSize(); } public void setConcurrentViewBuilders(int value) { if (value > viewBuildExecutor.getCorePoolSize()) { // we are increasing the value viewBuildExecutor.setMaximumPoolSize(value); viewBuildExecutor.setCorePoolSize(value); } else if (value < viewBuildExecutor.getCorePoolSize()) { // we are reducing the value viewBuildExecutor.setCorePoolSize(value); viewBuildExecutor.setMaximumPoolSize(value); } } public int getCoreCompactorThreads() { return executor.getCorePoolSize(); } public void setCoreCompactorThreads(int number) { executor.setCorePoolSize(number); } public int getMaximumCompactorThreads() { return executor.getMaximumPoolSize(); } public void setMaximumCompactorThreads(int number) { executor.setMaximumPoolSize(number); } public int getCoreValidationThreads() { return validationExecutor.getCorePoolSize(); } public void setCoreValidationThreads(int number) { validationExecutor.setCorePoolSize(number); } public int getMaximumValidatorThreads() { return validationExecutor.getMaximumPoolSize(); } public void setMaximumValidatorThreads(int number) { validationExecutor.setMaximumPoolSize(number); } public boolean getDisableSTCSInL0() { return DatabaseDescriptor.getDisableSTCSInL0(); } public void setDisableSTCSInL0(boolean disabled) { if (disabled != DatabaseDescriptor.getDisableSTCSInL0()) logger.info("Changing STCS in L0 disabled from {} to {}", DatabaseDescriptor.getDisableSTCSInL0(), disabled); DatabaseDescriptor.setDisableSTCSInL0(disabled); } public int getCoreViewBuildThreads() { return viewBuildExecutor.getCorePoolSize(); } public void setCoreViewBuildThreads(int number) { viewBuildExecutor.setCorePoolSize(number); } public int getMaximumViewBuildThreads() { return viewBuildExecutor.getMaximumPoolSize(); } public void setMaximumViewBuildThreads(int number) { viewBuildExecutor.setMaximumPoolSize(number); } public boolean getAutomaticSSTableUpgradeEnabled() { return DatabaseDescriptor.automaticSSTableUpgrade(); } public void setAutomaticSSTableUpgradeEnabled(boolean enabled) { DatabaseDescriptor.setAutomaticSSTableUpgradeEnabled(enabled); } public int getMaxConcurrentAutoUpgradeTasks() { return DatabaseDescriptor.maxConcurrentAutoUpgradeTasks(); } public void setMaxConcurrentAutoUpgradeTasks(int value) { try { DatabaseDescriptor.setMaxConcurrentAutoUpgradeTasks(value); } catch (ConfigurationException e) { throw new RuntimeException(e.getMessage()); } } /** * Try to stop all of the compactions for given ColumnFamilies. * * Note that this method does not wait for all compactions to finish; you'll need to loop against * isCompacting if you want that behavior. * * @param columnFamilies The ColumnFamilies to try to stop compaction upon. * @param sstablePredicate the sstable predicate to match on * @param interruptValidation true if validation operations for repair should also be interrupted */ public void interruptCompactionFor(Iterable columnFamilies, Predicate sstablePredicate, boolean interruptValidation) { assert columnFamilies != null; // interrupt in-progress compactions for (Holder compactionHolder : active.getCompactions()) { CompactionInfo info = compactionHolder.getCompactionInfo(); if ((info.getTaskType() == OperationType.VALIDATION) && !interruptValidation) continue; if (info.getTableMetadata() == null || Iterables.contains(columnFamilies, info.getTableMetadata())) { if (info.shouldStop(sstablePredicate)) compactionHolder.stop(); } } } public void interruptCompactionForCFs(Iterable cfss, Predicate sstablePredicate, boolean interruptValidation) { List metadata = new ArrayList<>(); for (ColumnFamilyStore cfs : cfss) metadata.add(cfs.metadata()); interruptCompactionFor(metadata, sstablePredicate, interruptValidation); } public void waitForCessation(Iterable cfss, Predicate sstablePredicate) { long start = System.nanoTime(); long delay = TimeUnit.MINUTES.toNanos(1); while (System.nanoTime() - start < delay) { if (CompactionManager.instance.isCompacting(cfss, sstablePredicate)) Uninterruptibles.sleepUninterruptibly(1, TimeUnit.MILLISECONDS); else break; } } public List getSSTableTasks() { return active.getCompactions() .stream() .map(CompactionInfo.Holder::getCompactionInfo) .filter(task -> task.getTaskType() != OperationType.COUNTER_CACHE_SAVE && task.getTaskType() != OperationType.KEY_CACHE_SAVE && task.getTaskType() != OperationType.ROW_CACHE_SAVE) .collect(Collectors.toList()); } /** * Return whether "global" compactions should be paused, used by ColumnFamilyStore#runWithCompactionsDisabled * * a global compaction is one that includes several/all tables, currently only IndexSummaryBuilder */ public boolean isGlobalCompactionPaused() { return globalCompactionPauseCount.get() > 0; } public CompactionPauser pauseGlobalCompaction() { CompactionPauser pauser = globalCompactionPauseCount::decrementAndGet; globalCompactionPauseCount.incrementAndGet(); return pauser; } public interface CompactionPauser extends AutoCloseable { public void close(); } }