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fetch_response.go
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fetch_response.go
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package healer
import (
"compress/gzip"
"context"
"encoding/binary"
"errors"
"fmt"
"io"
snappy "github.com/eapache/go-xerial-snappy"
"github.com/pierrec/lz4"
)
var errFetchResponseTooShortNoRecordsMeta = errors.New("fetch response too short, could not get records metadata(form baseOffset to baseSequence)")
type fetchResponseStreamDecoder struct {
ctx context.Context
totalLength int
offset int
buffers io.Reader
messages chan *FullMessage
more bool
version uint16
responsesCount int
correlationID int32
startOffset int64
hasOneMessage bool
}
func (streamDecoder *fetchResponseStreamDecoder) putMessage(msg *FullMessage) error {
select {
case <-streamDecoder.ctx.Done():
return streamDecoder.ctx.Err()
case streamDecoder.messages <- msg:
return nil
}
}
func (streamDecoder *fetchResponseStreamDecoder) readAll() (length int, err error) {
defer func() {
streamDecoder.offset += length
}()
written, err := io.Copy(io.Discard, streamDecoder.buffers)
return int(written), err
}
var errShortRead = errors.New("short read")
func (streamDecoder *fetchResponseStreamDecoder) Read(p []byte) (n int, err error) {
defer func() {
streamDecoder.offset += n
}()
return streamDecoder.buffers.Read(p)
}
// read util getting n bytes
func (streamDecoder *fetchResponseStreamDecoder) read(n int) (rst []byte, length int, err error) {
defer func() {
streamDecoder.offset += length
}()
rst = make([]byte, n)
length, err = io.ReadFull(streamDecoder.buffers, rst)
return rst, length, err
}
// uncompress read all remaining bytes and uncompress them
func uncompress(compress int8, reader io.Reader) (uncompressedBytes []byte, err error) {
switch compress {
case COMPRESSION_NONE:
uncompressedBytes, err = io.ReadAll(reader)
if err != nil {
return uncompressedBytes, fmt.Errorf("read uncompressed records bytes error: %w", err)
}
case COMPRESSION_GZIP:
reader, err := gzip.NewReader(reader)
if err != nil {
return nil, fmt.Errorf("create gzip reader of records bytes error: %w", err)
}
if uncompressedBytes, err = io.ReadAll(reader); err != nil && err != io.EOF {
return nil, fmt.Errorf("uncompress gzip records error: %w", err)
}
case COMPRESSION_SNAPPY:
buf, err := io.ReadAll(reader)
if err != nil {
return nil, fmt.Errorf("read streamDecoder error: %w", err)
}
uncompressedBytes, err = snappy.Decode(buf)
if err != nil {
return nil, fmt.Errorf("uncompress snappy records error: %w", err)
}
case COMPRESSION_LZ4:
reader := lz4.NewReader(reader)
uncompressedBytes, err = io.ReadAll(reader)
if err != nil {
return nil, fmt.Errorf("uncompress lz4 records error: %w", err)
}
}
return uncompressedBytes, nil
}
func (streamDecoder *fetchResponseStreamDecoder) decodeMessageSetMagic0or1(topicName string, partitionID int32, magic int, header17 []byte) (offset int, err error) {
firstMessageSet := true
// value is the bytes of whole record consists of (offset(int64) message_size(int32) message)
var value []byte
for {
if firstMessageSet {
firstMessageSet = false
// messageSize doesn't include the size of messageSize itself.
messageSize := int(binary.BigEndian.Uint32(header17[8:]))
if messageSize < 6 {
return
}
// 12 is the size of offset(int64) & message_size(int32) in header17
value = make([]byte, 12+messageSize)
n, e := streamDecoder.Read(value[17:])
offset += n
if e != nil {
return offset, e
}
// remaining bytes is incomplete
if n < len(value)-17 {
return offset, err
}
copy(value, header17)
} else {
buf, n, err := streamDecoder.read(12)
offset += n
if err != nil {
return offset, err
}
if n < 12 {
return offset, err
}
messageSize := int(binary.BigEndian.Uint32(buf[8:]))
value = make([]byte, 12+messageSize)
n, err = streamDecoder.Read(value[12:])
offset += n
if err != nil {
return offset, err
}
// remaining bytes is incomplete
if n < len(value)-17 {
return offset, err
}
copy(value, buf)
}
messageSet, err := DecodeToMessageSet(value)
if err != nil {
return offset, err
}
if len(messageSet) == 0 {
return offset, nil
}
// TODO send each message to the channel directly?
for i := range messageSet {
if messageSet[i].Offset >= streamDecoder.startOffset {
msg := &FullMessage{
TopicName: topicName,
PartitionID: partitionID,
Message: messageSet[i],
}
if err = streamDecoder.putMessage(msg); err != nil {
return offset, err
}
streamDecoder.hasOneMessage = true
} else {
logger.Info("offset smaller than startOffset", "offset", "topic", topicName, "partition", partitionID, messageSet[i].Offset, "startOffset", streamDecoder.startOffset)
}
}
}
}
// offset returned equals to batchLength + 12
func (streamDecoder *fetchResponseStreamDecoder) decodeRecordsMagic2(topicName string, partitionID int32, header17 []byte) (offset int, err error) {
bytesBeforeRecordsLength := 44 // (magic, records count]
bytesBeforeRecords, n, err := streamDecoder.read(bytesBeforeRecordsLength)
if err != nil {
if err == io.ErrUnexpectedEOF {
return n, nil
}
return n, err
}
offset += n
if n < bytesBeforeRecordsLength {
return offset, errFetchResponseTooShortNoRecordsMeta
}
buf := make([]byte, len(bytesBeforeRecords)+len(header17))
copy(buf, header17)
copy(buf[len(header17):], bytesBeforeRecords)
baseOffset := int64(binary.BigEndian.Uint64(buf))
batchLength := binary.BigEndian.Uint32(buf[8:])
// partitionLeaderEpoch := binary.BigEndian.Uint32(buf[12:])
// magic := buf[16]
// crc := binary.BigEndian.Uint32(buf[17:])
attributes := binary.BigEndian.Uint16(buf[21:])
compress := attributes & 0b11
// lastOffsetDelta := binary.BigEndian.Uint32(buf[23:])
baseTimestamp := binary.BigEndian.Uint64(buf[27:])
// maxTimestamp := binary.BigEndian.Uint64(buf[35:])
// producerID := binary.BigEndian.Uint64(buf[43:])
// producerEpoch := binary.BigEndian.Uint16(buf[51:])
// baseSequence := binary.BigEndian.Uint32(buf[53:])
// count is not accurate, payload maybe truncated by maxsize parameter in fetch request
count := int(binary.BigEndian.Uint32(buf[57:]))
if count <= 0 {
return
}
// 49 is length of (batchLength, records count]
if int(batchLength)-49 > streamDecoder.totalLength-streamDecoder.offset {
n, err = streamDecoder.readAll()
offset += n
return offset, err
}
r := io.LimitReader(streamDecoder, int64(batchLength)-49)
uncompressedBytes, err := uncompress(int8(compress), r)
if err != nil {
return offset, fmt.Errorf("uncompress records bytes error: %w", err)
}
offset += int(batchLength) - 49
uncompressedBytesOffset := 0
for i := 0; i < count; i++ {
record, o, err := DecodeToRecord(uncompressedBytes[uncompressedBytesOffset:])
if err != nil {
if err == errUncompleteRecord {
err = nil
}
return offset, err
}
uncompressedBytesOffset += o
message := &Message{
Offset: int64(record.offsetDelta) + baseOffset,
Timestamp: uint64(record.timestampDelta) + baseTimestamp,
Attributes: record.attributes,
MagicByte: 2,
Key: record.key,
Value: record.value,
Headers: record.Headers,
}
if message.Offset >= streamDecoder.startOffset {
msg := &FullMessage{
TopicName: topicName,
PartitionID: partitionID,
Message: message,
}
if err = streamDecoder.putMessage(msg); err != nil {
return offset, err
}
streamDecoder.hasOneMessage = true
}
}
return offset, nil
}
// messageSetSizeBytes may include more the one `Record Batch`,
// that is, `Record Batch`,`Record Batch`,`Record Batch`...
func (streamDecoder *fetchResponseStreamDecoder) decodeMessageSet(topicName string, partitionID int32, messageSetSizeBytes int32, version uint16) (err error) {
defer func() {
if err == io.EOF || err == &maxBytesTooSmall {
if streamDecoder.hasOneMessage {
err = nil
}
}
if !streamDecoder.hasOneMessage && err == nil {
err = &maxBytesTooSmall
}
}()
var (
offset int
o int
)
for offset < int(messageSetSizeBytes) {
// payload before magic
header17, n, e := streamDecoder.read(17)
if e != nil {
if e == io.ErrUnexpectedEOF {
return nil
}
return e
}
if n < 17 {
return
}
offset += n
magic := header17[16]
if magic < 2 {
o, err = streamDecoder.decodeMessageSetMagic0or1(topicName, partitionID, int(magic), header17)
} else {
o, err = streamDecoder.decodeRecordsMagic2(topicName, partitionID, header17)
}
offset += o
if err != nil {
// if err == errUncompleteRecord {
// hasAtLeastOneMessage = true
// return nil
// }
return err
}
}
return nil
}
func (streamDecoder *fetchResponseStreamDecoder) decodePartitionResponse(topicName string, version uint16) error {
var (
partition int32
errorCode int16
//highwaterMarkOffset int64
messageSetSizeBytes int32
err error
buffer []byte
n int
)
var bytesBeforeRecordsLength int // (partition_index, messageSetSizeBytes]
switch version {
case 0:
bytesBeforeRecordsLength = 18
case 7, 10:
bytesBeforeRecordsLength = 38
}
buffer, n, err = streamDecoder.read(bytesBeforeRecordsLength)
if err != nil {
return err
}
if n < bytesBeforeRecordsLength {
return &maxBytesTooSmall
}
partition = int32(binary.BigEndian.Uint32(buffer))
errorCode = int16(binary.BigEndian.Uint16(buffer[4:]))
if errorCode != 0 {
return KafkaError(errorCode)
}
messageSetSizeBytes = int32(binary.BigEndian.Uint32((buffer[bytesBeforeRecordsLength-4:])))
if messageSetSizeBytes == 0 {
return nil
}
// if we use fetch request with version 0 and not big enough fetch.max.bytes, kafka server may return partial records, and the NOT begins with the requests offset.
// healer will ignore the records, double fetch.max.bytes, and then retry.
if int(messageSetSizeBytes) > streamDecoder.totalLength-streamDecoder.offset {
return &maxBytesTooSmall
}
err = streamDecoder.decodeMessageSet(topicName, partition, messageSetSizeBytes, version)
return err
}
func (streamDecoder *fetchResponseStreamDecoder) decodeResponses(version uint16) error {
var (
err error
buffer []byte
)
buffer, _, err = streamDecoder.read(2)
if err != nil {
return err
}
topicNameLength := int(binary.BigEndian.Uint16(buffer))
buffer, _, err = streamDecoder.read(topicNameLength)
if err != nil {
return err
}
topicName := string(buffer)
buffer, _, err = streamDecoder.read(4)
if err != nil {
return err
}
partitionResponseCount := binary.BigEndian.Uint32(buffer)
if partitionResponseCount == 0 {
return &noPartitionResponse
}
for ; partitionResponseCount > 0; partitionResponseCount-- {
err = streamDecoder.decodePartitionResponse(topicName, version)
if err != nil {
return err
}
}
return nil
}
func (streamDecoder *fetchResponseStreamDecoder) decodeHeader(version uint16) error {
var (
headerLength int
countOffset int
)
switch version {
case 0:
headerLength = 8
countOffset = 4
case 7, 10:
headerLength = 18
countOffset = 14
}
buffer, n, err := streamDecoder.read(headerLength)
if err != nil {
return err
}
if n != headerLength {
return fmt.Errorf("could read enough bytes of fetch response header. read %d bytes", n)
}
streamDecoder.correlationID = int32(binary.BigEndian.Uint32(buffer))
streamDecoder.responsesCount = int(binary.BigEndian.Uint32(buffer[countOffset:]))
return nil
}
func (streamDecoder *fetchResponseStreamDecoder) streamDecode(ctx context.Context, startOffset int64) error {
streamDecoder.offset = 0
streamDecoder.startOffset = startOffset
streamDecoder.hasOneMessage = false
if err := streamDecoder.decodeHeader(streamDecoder.version); err != nil {
return err
}
if streamDecoder.responsesCount == 0 {
return nil
}
for i := 0; i < streamDecoder.responsesCount; i++ {
err := streamDecoder.decodeResponses(streamDecoder.version)
if err != nil {
msg := &FullMessage{
TopicName: "",
PartitionID: -1,
Error: err,
Message: nil,
}
select {
case <-ctx.Done():
return ctx.Err()
case <-streamDecoder.ctx.Done():
return streamDecoder.ctx.Err()
case streamDecoder.messages <- msg:
return nil
}
}
}
// 早期版本的协议可能会有多出来的字节,需要丢弃
if streamDecoder.more {
streamDecoder.readAll()
}
logger.V(5).Info("decode fetch response done", "correlationID", streamDecoder.correlationID)
return nil
}