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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.hints;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.StandardOpenOption;
import java.util.zip.CRC32;
import com.google.common.annotations.VisibleForTesting;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.io.FSWriteError;
import org.apache.cassandra.io.util.DataOutputBuffer;
import org.apache.cassandra.io.util.DataOutputBufferFixed;
import org.apache.cassandra.utils.NativeLibrary;
import org.apache.cassandra.utils.SyncUtil;
import org.apache.cassandra.utils.Throwables;
import static org.apache.cassandra.utils.FBUtilities.updateChecksum;
import static org.apache.cassandra.utils.FBUtilities.updateChecksumInt;
import static org.apache.cassandra.utils.Throwables.perform;
class HintsWriter implements AutoCloseable
{
static final int PAGE_SIZE = 4096;
private final File directory;
private final HintsDescriptor descriptor;
private final File file;
protected final FileChannel channel;
private final int fd;
protected final CRC32 globalCRC;
private volatile long lastSyncPosition = 0L;
protected HintsWriter(File directory, HintsDescriptor descriptor, File file, FileChannel channel, int fd, CRC32 globalCRC)
{
this.directory = directory;
this.descriptor = descriptor;
this.file = file;
this.channel = channel;
this.fd = fd;
this.globalCRC = globalCRC;
}
@SuppressWarnings("resource") // HintsWriter owns channel
static HintsWriter create(File directory, HintsDescriptor descriptor) throws IOException
{
File file = new File(directory, descriptor.fileName());
FileChannel channel = FileChannel.open(file.toPath(), StandardOpenOption.WRITE, StandardOpenOption.CREATE_NEW);
int fd = NativeLibrary.getfd(channel);
CRC32 crc = new CRC32();
try (DataOutputBuffer dob = DataOutputBuffer.scratchBuffer.get())
{
// write the descriptor
descriptor.serialize(dob);
ByteBuffer descriptorBytes = dob.buffer();
updateChecksum(crc, descriptorBytes);
channel.write(descriptorBytes);
if (descriptor.isEncrypted())
return new EncryptedHintsWriter(directory, descriptor, file, channel, fd, crc);
if (descriptor.isCompressed())
return new CompressedHintsWriter(directory, descriptor, file, channel, fd, crc);
return new HintsWriter(directory, descriptor, file, channel, fd, crc);
}
catch (Throwable e)
{
channel.close();
throw e;
}
}
HintsDescriptor descriptor()
{
return descriptor;
}
private void writeChecksum()
{
File checksumFile = new File(directory, descriptor.checksumFileName());
try (OutputStream out = Files.newOutputStream(checksumFile.toPath()))
{
out.write(Integer.toHexString((int) globalCRC.getValue()).getBytes(StandardCharsets.UTF_8));
}
catch (IOException e)
{
throw new FSWriteError(e, checksumFile);
}
}
public void close()
{
perform(file, Throwables.FileOpType.WRITE, this::doFsync, channel::close);
writeChecksum();
}
public void fsync()
{
perform(file, Throwables.FileOpType.WRITE, this::doFsync);
}
private void doFsync() throws IOException
{
SyncUtil.force(channel, true);
lastSyncPosition = channel.position();
}
Session newSession(ByteBuffer buffer)
{
try
{
return new Session(buffer, channel.size());
}
catch (IOException e)
{
throw new FSWriteError(e, file);
}
}
@VisibleForTesting
File getFile()
{
return file;
}
/**
* Writes byte buffer into the file channel. Buffer should be flipped before calling this
*/
protected void writeBuffer(ByteBuffer bb) throws IOException
{
updateChecksum(globalCRC, bb);
channel.write(bb);
}
/**
* The primary goal of the Session class is to be able to share the same buffers among potentially dozens or hundreds
* of hints writers, and ensure that their contents are always written to the underlying channels in the end.
*/
final class Session implements AutoCloseable
{
private final ByteBuffer buffer;
private final long initialSize;
private long bytesWritten;
Session(ByteBuffer buffer, long initialSize)
{
buffer.clear();
bytesWritten = 0L;
this.buffer = buffer;
this.initialSize = initialSize;
}
@VisibleForTesting
long getBytesWritten()
{
return bytesWritten;
}
long position()
{
return initialSize + bytesWritten;
}
/**
* Appends the serialized hint (with CRC included) to this session's aggregation buffer,
* writes to the underlying channel when the buffer is overflown.
*
* @param hint the serialized hint (with CRC included)
* @throws IOException
*/
void append(ByteBuffer hint) throws IOException
{
bytesWritten += hint.remaining();
// if the hint to write won't fit in the aggregation buffer, flush it
if (hint.remaining() > buffer.remaining())
{
buffer.flip();
writeBuffer(buffer);
buffer.clear();
}
// if the hint fits in the aggregation buffer, then update the aggregation buffer,
// otherwise write the hint buffer to the channel
if (hint.remaining() <= buffer.remaining())
{
buffer.put(hint);
}
else
{
writeBuffer(hint);
}
}
/**
* Serializes and appends the hint (with CRC included) to this session's aggregation buffer,
* writes to the underlying channel when the buffer is overflown.
*
* Used mainly by tests and {@link LegacyHintsMigrator}
*
* @param hint the unserialized hint
* @throws IOException
*/
void append(Hint hint) throws IOException
{
int hintSize = (int) Hint.serializer.serializedSize(hint, descriptor.messagingVersion());
int totalSize = hintSize + HintsBuffer.ENTRY_OVERHEAD_SIZE;
if (totalSize > buffer.remaining())
flushBuffer();
ByteBuffer hintBuffer = totalSize <= buffer.remaining()
? buffer
: ByteBuffer.allocate(totalSize);
CRC32 crc = new CRC32();
try (DataOutputBufferFixed out = new DataOutputBufferFixed(hintBuffer))
{
out.writeInt(hintSize);
updateChecksumInt(crc, hintSize);
out.writeInt((int) crc.getValue());
Hint.serializer.serialize(hint, out, descriptor.messagingVersion());
updateChecksum(crc, hintBuffer, hintBuffer.position() - hintSize, hintSize);
out.writeInt((int) crc.getValue());
}
if (hintBuffer == buffer)
bytesWritten += totalSize;
else
append((ByteBuffer) hintBuffer.flip());
}
/**
* Closes the session - flushes the aggregation buffer (if not empty), does page aligning, and potentially fsyncs.
* @throws IOException
*/
public void close() throws IOException
{
flushBuffer();
maybeFsync();
maybeSkipCache();
}
private void flushBuffer() throws IOException
{
buffer.flip();
if (buffer.remaining() > 0)
{
writeBuffer(buffer);
}
buffer.clear();
}
private void maybeFsync()
{
if (position() >= lastSyncPosition + DatabaseDescriptor.getTrickleFsyncIntervalInKb() * 1024L)
fsync();
}
private void maybeSkipCache()
{
long position = position();
// don't skip page cache for tiny files, on the assumption that if they are tiny, the target node is probably
// alive, and if so, the file will be closed and dispatched shortly (within a minute), and the file will be dropped.
if (position >= DatabaseDescriptor.getTrickleFsyncIntervalInKb() * 1024L)
NativeLibrary.trySkipCache(fd, 0, position - (position % PAGE_SIZE), file.getPath());
}
}
}