private void compactMemTableInternal() throws IOException {
Preconditions.checkState(mutex.isHeldByCurrentThread());
if (immutableMemTable == null) {
return;
}
try {
// Save the contents of the memtable as a new Table
VersionEdit edit = new VersionEdit();
Version base = versions.getCurrent();
writeLevel0Table(immutableMemTable, edit, base);
if (shuttingDown.get()) {
throw new DatabaseShutdownException("Database shutdown during memtable compaction");
}
// Replace immutable memtable with the generated Table
edit.setPreviousLogNumber(0);
edit.setLogNumber(log.getFileNumber()); // Earlier logs no longer needed
versions.logAndApply(edit);
immutableMemTable = null;
deleteObsoleteFiles();
} finally {
backgroundCondition.signalAll();
}
}
public DbImpl(Options options, File databaseDir) throws IOException {
Preconditions.checkNotNull(options, "options is null");
Preconditions.checkNotNull(databaseDir, "databaseDir is null");
this.options = options;
if (this.options.compressionType() == CompressionType.ZLIB && !Zlib.available()) {
// There's little hope to continue.
this.options.compressionType(CompressionType.NONE);
}
if (this.options.compressionType() == CompressionType.SNAPPY && !Snappy.available()) {
// Disable snappy if it's not available.
this.options.compressionType(CompressionType.NONE);
}
this.databaseDir = databaseDir;
// use custom comparator if set
DBComparator comparator = options.comparator();
UserComparator userComparator;
if (comparator != null) {
userComparator = new CustomUserComparator(comparator);
} else {
userComparator = new BytewiseComparator();
}
internalKeyComparator = new InternalKeyComparator(userComparator);
memTable = new MemTable(internalKeyComparator);
immutableMemTable = null;
ThreadFactory compactionThreadFactory =
new ThreadFactoryBuilder()
.setNameFormat("leveldb-compaction-%s")
.setUncaughtExceptionHandler(
new UncaughtExceptionHandler() {
@Override
public void uncaughtException(Thread t, Throwable e) {
// todo need a real UncaughtExceptionHandler
System.out.printf("%s%n", t);
e.printStackTrace();
}
})
.build();
compactionExecutor = Executors.newSingleThreadExecutor(compactionThreadFactory);
// Reserve ten files or so for other uses and give the rest to TableCache.
int tableCacheSize = options.maxOpenFiles() - 10;
tableCache =
new TableCache(
databaseDir,
tableCacheSize,
new InternalUserComparator(internalKeyComparator),
options.verifyChecksums());
// create the version set
// create the database dir if it does not already exist
databaseDir.mkdirs();
Preconditions.checkArgument(
databaseDir.exists(),
"Database directory '%s' does not exist and could not be created",
databaseDir);
Preconditions.checkArgument(
databaseDir.isDirectory(), "Database directory '%s' is not a directory", databaseDir);
mutex.lock();
try {
// lock the database dir
dbLock = new DbLock(new File(databaseDir, Filename.lockFileName()));
// verify the "current" file
File currentFile = new File(databaseDir, Filename.currentFileName());
if (!currentFile.canRead()) {
Preconditions.checkArgument(
options.createIfMissing(),
"Database '%s' does not exist and the create if missing option is disabled",
databaseDir);
} else {
Preconditions.checkArgument(
!options.errorIfExists(),
"Database '%s' exists and the error if exists option is enabled",
databaseDir);
}
versions = new VersionSet(databaseDir, tableCache, internalKeyComparator);
// load (and recover) current version
versions.recover();
// Recover from all newer log files than the ones named in the
// descriptor (new log files may have been added by the previous
// incarnation without registering them in the descriptor).
//
// Note that PrevLogNumber() is no longer used, but we pay
// attention to it in case we are recovering a database
// produced by an older version of leveldb.
long minLogNumber = versions.getLogNumber();
long previousLogNumber = versions.getPrevLogNumber();
List<File> filenames = Filename.listFiles(databaseDir);
List<Long> logs = Lists.newArrayList();
for (File filename : filenames) {
FileInfo fileInfo = Filename.parseFileName(filename);
if (fileInfo != null
&& fileInfo.getFileType() == FileType.LOG
&& ((fileInfo.getFileNumber() >= minLogNumber)
|| (fileInfo.getFileNumber() == previousLogNumber))) {
logs.add(fileInfo.getFileNumber());
}
}
// Recover in the order in which the logs were generated
VersionEdit edit = new VersionEdit();
Collections.sort(logs);
for (Long fileNumber : logs) {
long maxSequence = recoverLogFile(fileNumber, edit);
if (versions.getLastSequence() < maxSequence) {
versions.setLastSequence(maxSequence);
}
}
// open transaction log
long logFileNumber = versions.getNextFileNumber();
this.log =
Logs.createLogWriter(
new File(databaseDir, Filename.logFileName(logFileNumber)), logFileNumber);
edit.setLogNumber(log.getFileNumber());
// apply recovered edits
versions.logAndApply(edit);
// cleanup unused files
deleteObsoleteFiles();
// schedule compactions
maybeScheduleCompaction();
} finally {
mutex.unlock();
}
}