kafka LegacyRecord 源码
kafka LegacyRecord 代码
文件路径：/clients/src/main/java/org/apache/kafka/common/record/LegacyRecord.java
/*
* 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.kafka.common.record;
import java.util.zip.CRC32;
import org.apache.kafka.common.KafkaException;
import org.apache.kafka.common.errors.CorruptRecordException;
import org.apache.kafka.common.utils.ByteBufferOutputStream;
import org.apache.kafka.common.utils.ByteUtils;
import org.apache.kafka.common.utils.Checksums;
import org.apache.kafka.common.utils.Utils;
import java.io.DataOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import static org.apache.kafka.common.utils.Utils.wrapNullable;
/**
* This class represents the serialized key and value along with the associated CRC and other fields
* of message format versions 0 and 1. Note that it is uncommon to need to access this class directly.
* Usually it should be accessed indirectly through the {@link Record} interface which is exposed
* through the {@link Records} object.
*/
public final class LegacyRecord {
/**
* The current offset and size for all the fixed-length fields
*/
public static final int CRC_OFFSET = 0;
public static final int CRC_LENGTH = 4;
public static final int MAGIC_OFFSET = CRC_OFFSET + CRC_LENGTH;
public static final int MAGIC_LENGTH = 1;
public static final int ATTRIBUTES_OFFSET = MAGIC_OFFSET + MAGIC_LENGTH;
public static final int ATTRIBUTES_LENGTH = 1;
public static final int TIMESTAMP_OFFSET = ATTRIBUTES_OFFSET + ATTRIBUTES_LENGTH;
public static final int TIMESTAMP_LENGTH = 8;
public static final int KEY_SIZE_OFFSET_V0 = ATTRIBUTES_OFFSET + ATTRIBUTES_LENGTH;
public static final int KEY_SIZE_OFFSET_V1 = TIMESTAMP_OFFSET + TIMESTAMP_LENGTH;
public static final int KEY_SIZE_LENGTH = 4;
public static final int KEY_OFFSET_V0 = KEY_SIZE_OFFSET_V0 + KEY_SIZE_LENGTH;
public static final int KEY_OFFSET_V1 = KEY_SIZE_OFFSET_V1 + KEY_SIZE_LENGTH;
public static final int VALUE_SIZE_LENGTH = 4;
/**
* The size for the record header
*/
public static final int HEADER_SIZE_V0 = CRC_LENGTH + MAGIC_LENGTH + ATTRIBUTES_LENGTH;
public static final int HEADER_SIZE_V1 = CRC_LENGTH + MAGIC_LENGTH + ATTRIBUTES_LENGTH + TIMESTAMP_LENGTH;
/**
* The amount of overhead bytes in a record
*/
public static final int RECORD_OVERHEAD_V0 = HEADER_SIZE_V0 + KEY_SIZE_LENGTH + VALUE_SIZE_LENGTH;
/**
* The amount of overhead bytes in a record
*/
public static final int RECORD_OVERHEAD_V1 = HEADER_SIZE_V1 + KEY_SIZE_LENGTH + VALUE_SIZE_LENGTH;
/**
* Specifies the mask for the compression code. 3 bits to hold the compression codec. 0 is reserved to indicate no
* compression
*/
private static final int COMPRESSION_CODEC_MASK = 0x07;
/**
* Specify the mask of timestamp type: 0 for CreateTime, 1 for LogAppendTime.
*/
private static final byte TIMESTAMP_TYPE_MASK = 0x08;
/**
* Timestamp value for records without a timestamp
*/
public static final long NO_TIMESTAMP = -1L;
private final ByteBuffer buffer;
private final Long wrapperRecordTimestamp;
private final TimestampType wrapperRecordTimestampType;
public LegacyRecord(ByteBuffer buffer) {
this(buffer, null, null);
}
public LegacyRecord(ByteBuffer buffer, Long wrapperRecordTimestamp, TimestampType wrapperRecordTimestampType) {
this.buffer = buffer;
this.wrapperRecordTimestamp = wrapperRecordTimestamp;
this.wrapperRecordTimestampType = wrapperRecordTimestampType;
}
/**
* Compute the checksum of the record from the record contents
*/
public long computeChecksum() {
return crc32(buffer, MAGIC_OFFSET, buffer.limit() - MAGIC_OFFSET);
}
/**
* Retrieve the previously computed CRC for this record
*/
public long checksum() {
return ByteUtils.readUnsignedInt(buffer, CRC_OFFSET);
}
/**
* Returns true if the crc stored with the record matches the crc computed off the record contents
*/
public boolean isValid() {
return sizeInBytes() >= RECORD_OVERHEAD_V0 && checksum() == computeChecksum();
}
public Long wrapperRecordTimestamp() {
return wrapperRecordTimestamp;
}
public TimestampType wrapperRecordTimestampType() {
return wrapperRecordTimestampType;
}
/**
* Throw an InvalidRecordException if isValid is false for this record
*/
public void ensureValid() {
if (sizeInBytes() < RECORD_OVERHEAD_V0)
throw new CorruptRecordException("Record is corrupt (crc could not be retrieved as the record is too "
+ "small, size = " + sizeInBytes() + ")");
if (!isValid())
throw new CorruptRecordException("Record is corrupt (stored crc = " + checksum()
+ ", computed crc = " + computeChecksum() + ")");
}
/**
* The complete serialized size of this record in bytes (including crc, header attributes, etc), but
* excluding the log overhead (offset and record size).
* @return the size in bytes
*/
public int sizeInBytes() {
return buffer.limit();
}
/**
* The length of the key in bytes
* @return the size in bytes of the key (0 if the key is null)
*/
public int keySize() {
if (magic() == RecordBatch.MAGIC_VALUE_V0)
return buffer.getInt(KEY_SIZE_OFFSET_V0);
else
return buffer.getInt(KEY_SIZE_OFFSET_V1);
}
/**
* Does the record have a key?
* @return true if so, false otherwise
*/
public boolean hasKey() {
return keySize() >= 0;
}
/**
* The position where the value size is stored
*/
private int valueSizeOffset() {
if (magic() == RecordBatch.MAGIC_VALUE_V0)
return KEY_OFFSET_V0 + Math.max(0, keySize());
else
return KEY_OFFSET_V1 + Math.max(0, keySize());
}
/**
* The length of the value in bytes
* @return the size in bytes of the value (0 if the value is null)
*/
public int valueSize() {
return buffer.getInt(valueSizeOffset());
}
/**
* Check whether the value field of this record is null.
* @return true if the value is null, false otherwise
*/
public boolean hasNullValue() {
return valueSize() < 0;
}
/**
* The magic value (i.e. message format version) of this record
* @return the magic value
*/
public byte magic() {
return buffer.get(MAGIC_OFFSET);
}
/**
* The attributes stored with this record
* @return the attributes
*/
public byte attributes() {
return buffer.get(ATTRIBUTES_OFFSET);
}
/**
* When magic value is greater than 0, the timestamp of a record is determined in the following way:
* 1. wrapperRecordTimestampType = null and wrapperRecordTimestamp is null - Uncompressed message, timestamp is in the message.
* 2. wrapperRecordTimestampType = LOG_APPEND_TIME and WrapperRecordTimestamp is not null - Compressed message using LOG_APPEND_TIME
* 3. wrapperRecordTimestampType = CREATE_TIME and wrapperRecordTimestamp is not null - Compressed message using CREATE_TIME
*
* @return the timestamp as determined above
*/
public long timestamp() {
if (magic() == RecordBatch.MAGIC_VALUE_V0)
return RecordBatch.NO_TIMESTAMP;
else {
// case 2
if (wrapperRecordTimestampType == TimestampType.LOG_APPEND_TIME && wrapperRecordTimestamp != null)
return wrapperRecordTimestamp;
// Case 1, 3
else
return buffer.getLong(TIMESTAMP_OFFSET);
}
}
/**
* Get the timestamp type of the record.
*
* @return The timestamp type or {@link TimestampType#NO_TIMESTAMP_TYPE} if the magic is 0.
*/
public TimestampType timestampType() {
return timestampType(magic(), wrapperRecordTimestampType, attributes());
}
/**
* The compression type used with this record
*/
public CompressionType compressionType() {
return CompressionType.forId(buffer.get(ATTRIBUTES_OFFSET) & COMPRESSION_CODEC_MASK);
}
/**
* A ByteBuffer containing the value of this record
* @return the value or null if the value for this record is null
*/
public ByteBuffer value() {
return Utils.sizeDelimited(buffer, valueSizeOffset());
}
/**
* A ByteBuffer containing the message key
* @return the buffer or null if the key for this record is null
*/
public ByteBuffer key() {
if (magic() == RecordBatch.MAGIC_VALUE_V0)
return Utils.sizeDelimited(buffer, KEY_SIZE_OFFSET_V0);
else
return Utils.sizeDelimited(buffer, KEY_SIZE_OFFSET_V1);
}
/**
* Get the underlying buffer backing this record instance.
*
* @return the buffer
*/
public ByteBuffer buffer() {
return this.buffer;
}
public String toString() {
if (magic() > 0)
return String.format("Record(magic=%d, attributes=%d, compression=%s, crc=%d, %s=%d, key=%d bytes, value=%d bytes)",
magic(),
attributes(),
compressionType(),
checksum(),
timestampType(),
timestamp(),
key() == null ? 0 : key().limit(),
value() == null ? 0 : value().limit());
else
return String.format("Record(magic=%d, attributes=%d, compression=%s, crc=%d, key=%d bytes, value=%d bytes)",
magic(),
attributes(),
compressionType(),
checksum(),
key() == null ? 0 : key().limit(),
value() == null ? 0 : value().limit());
}
public boolean equals(Object other) {
if (this == other)
return true;
if (other == null)
return false;
if (!other.getClass().equals(LegacyRecord.class))
return false;
LegacyRecord record = (LegacyRecord) other;
return this.buffer.equals(record.buffer);
}
public int hashCode() {
return buffer.hashCode();
}
/**
* Create a new record instance. If the record's compression type is not none, then
* its value payload should be already compressed with the specified type; the constructor
* would always write the value payload as is and will not do the compression itself.
*
* @param magic The magic value to use
* @param timestamp The timestamp of the record
* @param key The key of the record (null, if none)
* @param value The record value
* @param compressionType The compression type used on the contents of the record (if any)
* @param timestampType The timestamp type to be used for this record
*/
public static LegacyRecord create(byte magic,
long timestamp,
byte[] key,
byte[] value,
CompressionType compressionType,
TimestampType timestampType) {
int keySize = key == null ? 0 : key.length;
int valueSize = value == null ? 0 : value.length;
ByteBuffer buffer = ByteBuffer.allocate(recordSize(magic, keySize, valueSize));
write(buffer, magic, timestamp, wrapNullable(key), wrapNullable(value), compressionType, timestampType);
buffer.rewind();
return new LegacyRecord(buffer);
}
public static LegacyRecord create(byte magic, long timestamp, byte[] key, byte[] value) {
return create(magic, timestamp, key, value, CompressionType.NONE, TimestampType.CREATE_TIME);
}
/**
* Write the header for a compressed record set in-place (i.e. assuming the compressed record data has already
* been written at the value offset in a wrapped record). This lets you dynamically create a compressed message
* set, and then go back later and fill in its size and CRC, which saves the need for copying to another buffer.
*
* @param buffer The buffer containing the compressed record data positioned at the first offset of the
* @param magic The magic value of the record set
* @param recordSize The size of the record (including record overhead)
* @param timestamp The timestamp of the wrapper record
* @param compressionType The compression type used
* @param timestampType The timestamp type of the wrapper record
*/
public static void writeCompressedRecordHeader(ByteBuffer buffer,
byte magic,
int recordSize,
long timestamp,
CompressionType compressionType,
TimestampType timestampType) {
int recordPosition = buffer.position();
int valueSize = recordSize - recordOverhead(magic);
// write the record header with a null value (the key is always null for the wrapper)
write(buffer, magic, timestamp, null, null, compressionType, timestampType);
buffer.position(recordPosition);
// now fill in the value size
buffer.putInt(recordPosition + keyOffset(magic), valueSize);
// compute and fill the crc from the beginning of the message
long crc = crc32(buffer, MAGIC_OFFSET, recordSize - MAGIC_OFFSET);
ByteUtils.writeUnsignedInt(buffer, recordPosition + CRC_OFFSET, crc);
}
private static void write(ByteBuffer buffer,
byte magic,
long timestamp,
ByteBuffer key,
ByteBuffer value,
CompressionType compressionType,
TimestampType timestampType) {
try {
DataOutputStream out = new DataOutputStream(new ByteBufferOutputStream(buffer));
write(out, magic, timestamp, key, value, compressionType, timestampType);
} catch (IOException e) {
throw new KafkaException(e);
}
}
/**
* Write the record data with the given compression type and return the computed crc.
*
* @param out The output stream to write to
* @param magic The magic value to be used
* @param timestamp The timestamp of the record
* @param key The record key
* @param value The record value
* @param compressionType The compression type
* @param timestampType The timestamp type
* @return the computed CRC for this record.
* @throws IOException for any IO errors writing to the output stream.
*/
public static long write(DataOutputStream out,
byte magic,
long timestamp,
byte[] key,
byte[] value,
CompressionType compressionType,
TimestampType timestampType) throws IOException {
return write(out, magic, timestamp, wrapNullable(key), wrapNullable(value), compressionType, timestampType);
}
public static long write(DataOutputStream out,
byte magic,
long timestamp,
ByteBuffer key,
ByteBuffer value,
CompressionType compressionType,
TimestampType timestampType) throws IOException {
byte attributes = computeAttributes(magic, compressionType, timestampType);
long crc = computeChecksum(magic, attributes, timestamp, key, value);
write(out, magic, crc, attributes, timestamp, key, value);
return crc;
}
/**
* Write a record using raw fields (without validation). This should only be used in testing.
*/
public static void write(DataOutputStream out,
byte magic,
long crc,
byte attributes,
long timestamp,
byte[] key,
byte[] value) throws IOException {
write(out, magic, crc, attributes, timestamp, wrapNullable(key), wrapNullable(value));
}
// Write a record to the buffer, if the record's compression type is none, then
// its value payload should be already compressed with the specified type
private static void write(DataOutputStream out,
byte magic,
long crc,
byte attributes,
long timestamp,
ByteBuffer key,
ByteBuffer value) throws IOException {
if (magic != RecordBatch.MAGIC_VALUE_V0 && magic != RecordBatch.MAGIC_VALUE_V1)
throw new IllegalArgumentException("Invalid magic value " + magic);
if (timestamp < 0 && timestamp != RecordBatch.NO_TIMESTAMP)
throw new IllegalArgumentException("Invalid message timestamp " + timestamp);
// write crc
out.writeInt((int) (crc & 0xffffffffL));
// write magic value
out.writeByte(magic);
// write attributes
out.writeByte(attributes);
// maybe write timestamp
if (magic > RecordBatch.MAGIC_VALUE_V0)
out.writeLong(timestamp);
// write the key
if (key == null) {
out.writeInt(-1);
} else {
int size = key.remaining();
out.writeInt(size);
Utils.writeTo(out, key, size);
}
// write the value
if (value == null) {
out.writeInt(-1);
} else {
int size = value.remaining();
out.writeInt(size);
Utils.writeTo(out, value, size);
}
}
static int recordSize(byte magic, ByteBuffer key, ByteBuffer value) {
return recordSize(magic, key == null ? 0 : key.limit(), value == null ? 0 : value.limit());
}
public static int recordSize(byte magic, int keySize, int valueSize) {
return recordOverhead(magic) + keySize + valueSize;
}
// visible only for testing
public static byte computeAttributes(byte magic, CompressionType type, TimestampType timestampType) {
byte attributes = 0;
if (type.id > 0)
attributes |= COMPRESSION_CODEC_MASK & type.id;
if (magic > RecordBatch.MAGIC_VALUE_V0) {
if (timestampType == TimestampType.NO_TIMESTAMP_TYPE)
throw new IllegalArgumentException("Timestamp type must be provided to compute attributes for " +
"message format v1");
if (timestampType == TimestampType.LOG_APPEND_TIME)
attributes |= TIMESTAMP_TYPE_MASK;
}
return attributes;
}
// visible only for testing
public static long computeChecksum(byte magic, byte attributes, long timestamp, byte[] key, byte[] value) {
return computeChecksum(magic, attributes, timestamp, wrapNullable(key), wrapNullable(value));
}
private static long crc32(ByteBuffer buffer, int offset, int size) {
CRC32 crc = new CRC32();
Checksums.update(crc, buffer, offset, size);
return crc.getValue();
}
/**
* Compute the checksum of the record from the attributes, key and value payloads
*/
private static long computeChecksum(byte magic, byte attributes, long timestamp, ByteBuffer key, ByteBuffer value) {
CRC32 crc = new CRC32();
crc.update(magic);
crc.update(attributes);
if (magic > RecordBatch.MAGIC_VALUE_V0)
Checksums.updateLong(crc, timestamp);
// update for the key
if (key == null) {
Checksums.updateInt(crc, -1);
} else {
int size = key.remaining();
Checksums.updateInt(crc, size);
Checksums.update(crc, key, size);
}
// update for the value
if (value == null) {
Checksums.updateInt(crc, -1);
} else {
int size = value.remaining();
Checksums.updateInt(crc, size);
Checksums.update(crc, value, size);
}
return crc.getValue();
}
static int recordOverhead(byte magic) {
if (magic == 0)
return RECORD_OVERHEAD_V0;
else if (magic == 1)
return RECORD_OVERHEAD_V1;
throw new IllegalArgumentException("Invalid magic used in LegacyRecord: " + magic);
}
static int headerSize(byte magic) {
if (magic == 0)
return HEADER_SIZE_V0;
else if (magic == 1)
return HEADER_SIZE_V1;
throw new IllegalArgumentException("Invalid magic used in LegacyRecord: " + magic);
}
private static int keyOffset(byte magic) {
if (magic == 0)
return KEY_OFFSET_V0;
else if (magic == 1)
return KEY_OFFSET_V1;
throw new IllegalArgumentException("Invalid magic used in LegacyRecord: " + magic);
}
public static TimestampType timestampType(byte magic, TimestampType wrapperRecordTimestampType, byte attributes) {
if (magic == 0)
return TimestampType.NO_TIMESTAMP_TYPE;
else if (wrapperRecordTimestampType != null)
return wrapperRecordTimestampType;
else
return (attributes & TIMESTAMP_TYPE_MASK) == 0 ? TimestampType.CREATE_TIME : TimestampType.LOG_APPEND_TIME;
}
}
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