/*
* Copyright 2017-present Open Networking Foundation
*
* Licensed 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 io.atomix.storage.journal;
import com.esotericsoftware.kryo.KryoException;
import io.atomix.storage.journal.index.JournalIndex;
import java.io.IOException;
import java.nio.BufferOverflowException;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.zip.CRC32;
/**
* Segment writer.
*
* The format of an entry in the log is as follows:
*
* - 64-bit index
* - 8-bit boolean indicating whether a term change is contained in the entry
* - 64-bit optional term
* - 32-bit signed entry length, including the entry type ID
* - 8-bit signed entry type ID
* - n-bit entry bytes
*
*
* @author Jordan Halterman
*/
final class FileChannelJournalSegmentWriter extends JournalSegmentWriter {
private static final ByteBuffer ZERO_ENTRY_HEADER = ByteBuffer.wrap(new byte[Integer.BYTES + Integer.BYTES]);
private final FileChannel channel;
private final ByteBuffer memory;
private Indexed lastEntry;
private long currentPosition;
FileChannelJournalSegmentWriter(
FileChannel channel,
JournalSegment segment,
int maxEntrySize,
JournalIndex index,
JournalSerdes namespace) {
super(segment, maxEntrySize, index, namespace);
this.channel = channel;
this.memory = ByteBuffer.allocate((maxEntrySize + Integer.BYTES + Integer.BYTES) * 2);
memory.limit(0);
reset(0);
}
@Override
MappedByteBuffer buffer() {
return null;
}
@Override
public void reset(long index) {
long nextIndex = firstIndex;
// Clear the buffer indexes.
currentPosition = JournalSegmentDescriptor.BYTES;
try {
// Clear memory buffer and read fist chunk
memory.clear();
channel.read(memory, JournalSegmentDescriptor.BYTES);
memory.flip();
// Read the entry length.
int length = memory.getInt();
// If the length is non-zero, read the entry.
while (0 < length && length <= maxEntrySize && (index == 0 || nextIndex <= index)) {
// Read the checksum of the entry.
final long checksum = memory.getInt() & 0xFFFFFFFFL;
// Slice off the entry's bytes
final ByteBuffer entryBytes = memory.slice();
entryBytes.limit(length);
// Compute the checksum for the entry bytes.
final CRC32 crc32 = new CRC32();
crc32.update(entryBytes);
// If the stored checksum does not equal the computed checksum, do not proceed further
if (checksum != crc32.getValue()) {
break;
}
entryBytes.rewind();
final E entry = namespace.deserialize(entryBytes);
lastEntry = new Indexed<>(nextIndex, entry, length);
this.index.index(nextIndex, (int) currentPosition);
nextIndex++;
// Update the current position for indexing.
currentPosition = currentPosition + Integer.BYTES + Integer.BYTES + length;
memory.position(memory.position() + length);
// Read more bytes from the segment if necessary.
if (memory.remaining() < maxEntrySize) {
memory.clear();
channel.read(memory, currentPosition);
memory.flip();
}
length = memory.getInt();
}
} catch (BufferUnderflowException e) {
// No-op, position is only updated on success
} catch (IOException e) {
throw new StorageException(e);
}
}
@Override
public long getLastIndex() {
return lastEntry != null ? lastEntry.index() : segment.index() - 1;
}
@Override
public Indexed getLastEntry() {
return lastEntry;
}
@Override
public long getNextIndex() {
if (lastEntry != null) {
return lastEntry.index() + 1;
} else {
return firstIndex;
}
}
@Override
public void append(Indexed entry) {
final long nextIndex = getNextIndex();
// If the entry's index is greater than the next index in the segment, skip some entries.
if (entry.index() > nextIndex) {
throw new IndexOutOfBoundsException("Entry index is not sequential");
}
// If the entry's index is less than the next index, truncate the segment.
if (entry.index() < nextIndex) {
truncate(entry.index() - 1);
}
append(entry.entry());
}
@Override
@SuppressWarnings("unchecked")
public Indexed append(T entry) {
// Store the entry index.
final long index = getNextIndex();
// Serialize the entry.
memory.clear();
memory.position(Integer.BYTES + Integer.BYTES);
try {
namespace.serialize(entry, memory);
} catch (KryoException e) {
throw new StorageException.TooLarge("Entry size exceeds maximum allowed bytes (" + maxEntrySize + ")");
}
memory.flip();
final int length = memory.limit() - (Integer.BYTES + Integer.BYTES);
// Ensure there's enough space left in the buffer to store the entry.
if (segment.descriptor().maxSegmentSize() - currentPosition < length + Integer.BYTES + Integer.BYTES) {
throw new BufferOverflowException();
}
// If the entry length exceeds the maximum entry size then throw an exception.
if (length > maxEntrySize) {
throw new StorageException.TooLarge("Entry size " + length + " exceeds maximum allowed bytes (" + maxEntrySize + ")");
}
// Compute the checksum for the entry.
final CRC32 crc32 = new CRC32();
crc32.update(memory.array(), Integer.BYTES + Integer.BYTES, memory.limit() - (Integer.BYTES + Integer.BYTES));
final long checksum = crc32.getValue();
// Create a single byte[] in memory for the entire entry and write it as a batch to the underlying buffer.
memory.putInt(0, length);
memory.putInt(Integer.BYTES, (int) checksum);
try {
channel.write(memory, currentPosition);
} catch (IOException e) {
throw new StorageException(e);
}
// Update the last entry with the correct index/term/length.
Indexed indexedEntry = new Indexed<>(index, entry, length);
this.lastEntry = indexedEntry;
this.index.index(index, (int) currentPosition);
currentPosition = currentPosition + Integer.BYTES + Integer.BYTES + length;
return (Indexed) indexedEntry;
}
@Override
public void truncate(long index) {
// If the index is greater than or equal to the last index, skip the truncate.
if (index >= getLastIndex()) {
return;
}
// Reset the last entry.
lastEntry = null;
// Truncate the index.
this.index.truncate(index);
try {
if (index < segment.index()) {
// Reset the writer to the first entry.
currentPosition = JournalSegmentDescriptor.BYTES;
} else {
// Reset the writer to the given index.
reset(index);
}
// Zero the entry header at current channel position.
channel.write(ZERO_ENTRY_HEADER.asReadOnlyBuffer(), currentPosition);
} catch (IOException e) {
throw new StorageException(e);
}
}
@Override
public void flush() {
try {
if (channel.isOpen()) {
channel.force(true);
}
} catch (IOException e) {
throw new StorageException(e);
}
}
@Override
public void close() {
flush();
}
}