worryg0d commented on code in PR #1946:
URL:
https://github.com/apache/cassandra-gocql-driver/pull/1946#discussion_r3273090758
##########
conn.go:
##########
@@ -2047,6 +1937,343 @@ func (c *Conn) awaitSchemaAgreementWithTimeout(ctx
context.Context, timeout time
return fmt.Errorf("gocql: cluster schema versions not consistent: %+v",
schemas)
}
+// segmentWriter allows batching multiple frames into a signle segment before
flushing them to the connection.
+type segmentWriter struct {
+ w contextWriter
+ quit <-chan struct{}
+
+ // Holds write requests for the current segment.
+ writeRequests []writeRequest
+ totalFramesLength int
+ writeCh chan writeRequest
+
+ segmentCodec segmentCodec
+}
+
+func newSegmentWriter(w contextWriter, writeInterval time.Duration, quit
<-chan struct{}, compressor Compressor) *segmentWriter {
+ sw := &segmentWriter{
+ w: w,
+ quit: quit,
+ writeCh: make(chan writeRequest),
+ segmentCodec: newSegmentCodec(compressor),
+ }
+
+ go sw.runFlusher(writeInterval)
+
+ return sw
+}
+
+func (sw *segmentWriter) writeContext(ctx context.Context, frame []byte) (int,
error) {
+ resultChan := make(chan writeResult, 1)
+ req := writeRequest{
+ resultChan: resultChan,
+ data: frame,
+ }
+
+ select {
+ case <-ctx.Done():
+ return 0, ctx.Err()
+ case <-sw.quit:
+ return 0, ErrConnectionClosed
+ case sw.writeCh <- req:
+ // Enqueued for writing
+ }
+
+ result := <-resultChan
+ return result.n, result.err
+}
+
+func (sw *segmentWriter) runFlusher(interval time.Duration) {
+ timer := time.NewTimer(interval)
+ defer timer.Stop()
+
+ if !timer.Stop() {
+ <-timer.C
+ }
+
+ // Indicates whether the flush timer is running
+ running := false
+
+ for {
+ select {
+ case <-sw.quit:
+ return
+ case req := <-sw.writeCh:
+ frame := req.data
+ if len(frame) > maxSegmentPayloadSize {
+ sw.flushBigFrameImmediately(req)
+ } else if sw.fitsSegment(frame) {
+ sw.appendWriteRequest(req)
+ if !running {
+ running = true
+ timer.Reset(interval)
+ }
+ } else {
+ // Frame doesn't fit into current segment,
+ // so we need to flush the current one and
start a new one
+ sw.flushCurrentSegment()
+ sw.reset()
+ sw.appendWriteRequest(req)
+ timer.Reset(interval)
+ }
+ case <-timer.C:
+ running = false
+ sw.flushCurrentSegment()
+ sw.reset()
+ }
+ }
+}
+
+func (sw *segmentWriter) appendWriteRequest(req writeRequest) {
+ sw.writeRequests = append(sw.writeRequests, req)
+ sw.totalFramesLength += len(req.data)
+}
+
+func (sw *segmentWriter) fitsSegment(frame []byte) bool {
+ return sw.totalFramesLength+len(frame) <= maxSegmentPayloadSize
+}
+
+// Flushes the current segment and writes the results to the result listeners.
+// Should be called before resetting the segment writer.
+func (sw *segmentWriter) flushCurrentSegment() {
+ framesBuf := make([]byte, 0, sw.totalFramesLength)
+ for _, req := range sw.writeRequests {
+ // TODO: interesting if compiler optimizes this
+ framesBuf = append(framesBuf, req.data...)
+ }
+
+ err := sw.encodeAndWrite(framesBuf, true)
+ if err != nil {
+ for _, req := range sw.writeRequests {
+ req.resultChan <- writeResult{
+ n: 0,
+ err: err,
+ }
+ }
+ return
+ }
+
+ for _, req := range sw.writeRequests {
+ req.resultChan <- writeResult{
+ n: len(req.data),
+ err: nil,
+ }
+ }
+}
+
+func (sw *segmentWriter) reset() {
+ sw.writeRequests = nil
+ sw.totalFramesLength = 0
+}
+
+// Encodes a big frame which size is larger than maxSegmentPayloadSize
+// into multiple non self-contained segments and flushes them immediately
+func (sw *segmentWriter) flushBigFrameImmediately(req writeRequest) {
+ // Calculate the number of segment the frame will be split into
+ segmentsCount := 0
+ frame := req.data
+ frameLength := len(frame)
+ exactFit := frameLength%maxSegmentPayloadSize == 0
+ if exactFit {
+ segmentsCount = frameLength / maxSegmentPayloadSize
+ } else {
+ // An extra segment for the remainder of the frame
+ segmentsCount = frameLength/maxSegmentPayloadSize + 1
+ }
+
+ var flushErr error
+
+ for i := 0; i < segmentsCount; i++ {
+ // Calculate the length of the current frame part which will be
encoded into a segment
+ partialFrameLength := 0
+ if i < segmentsCount-1 || exactFit {
+ partialFrameLength = maxSegmentPayloadSize
+ } else {
+ partialFrameLength = frameLength % maxSegmentPayloadSize
+ }
+ err := sw.encodeAndWrite(frame[:partialFrameLength], false)
+ if err != nil {
+ flushErr = err
+ break
+ }
+ frame = frame[partialFrameLength:]
+ }
+
+ written := len(req.data)
+ if flushErr != nil {
+ written = 0
+ }
+
+ req.resultChan <- writeResult{
+ n: written,
+ err: flushErr,
+ }
+}
+
+// Encodes a frame into a segment and writes it to the underlying connection
+func (sw *segmentWriter) encodeAndWrite(frame []byte, isSelfContained bool)
error {
+ segmentBuf, err := sw.segmentCodec.encode(frame, isSelfContained)
+ if err != nil {
+ return err
+ }
+ _, err = sw.w.writeContext(context.Background(), segmentBuf)
+ if err != nil {
+ return err
+ }
+ return nil
+}
+
+// segmentReader allows reading segments from the underlying connection.
+// Implements ConnReader interface.
+type segmentReader struct {
+ r ConnReader
+
+ segmentCodec segmentCodec
+
+ // Reusable buffer for decoded frames
+ // This buffer might have multiple frames inside if self-contained
segment is decoded
+ readBufferDecoded bytes.Reader
+ // Reusable buffer for reading frame header
+ frameHeaderBuf [frameHeadSize]byte
+}
+
+func newSegmentReader(r ConnReader, segmentCodec segmentCodec) *segmentReader {
+ return &segmentReader{
+ r: r,
+ segmentCodec: segmentCodec,
+ }
+}
+
+// why do we have a write method for reader lol
+func (sr *segmentReader) Write(b []byte) (n int, err error) {
+ return sr.r.Write(b)
+}
+
+func (sr *segmentReader) Close() error {
+ return sr.r.Close()
+}
+
+func (sr *segmentReader) LocalAddr() net.Addr {
+ return sr.r.LocalAddr()
+}
+
+func (sr *segmentReader) RemoteAddr() net.Addr {
+ return sr.r.RemoteAddr()
+}
+
+func (sr *segmentReader) SetDeadline(t time.Time) error {
+ return sr.r.SetDeadline(t)
+}
+
+func (sr *segmentReader) SetReadDeadline(t time.Time) error {
+ return sr.r.SetReadDeadline(t)
+}
+
+func (sr *segmentReader) SetWriteDeadline(t time.Time) error {
+ return sr.r.SetWriteDeadline(t)
+}
+
+func (sr *segmentReader) SetTimeout(timeout time.Duration) {
+ sr.r.SetTimeout(timeout)
+}
+
+func (sr *segmentReader) GetTimeout() time.Duration {
+ return sr.r.GetTimeout()
+}
+
+func (sr *segmentReader) Read(p []byte) (n int, err error) {
+ // If we don't have a read buffer, or it's empty, read the first
segment.
+ // If we have read all the frames from the current segment, read the
next segment.
+ // If segment is non self-container, it will read all segments and read
buffer will hold the full frame.
+ if sr.readBufferDecoded.Len() == 0 {
+ err = sr.readSegment()
+ if err != nil {
+ return 0, err
+ }
+ }
+
+ return sr.readBufferDecoded.Read(p)
+}
+
+func (sr *segmentReader) readSegment() error {
+ segment, isSelfContained, err := sr.segmentCodec.decode(sr.r)
+ if err != nil {
+ // TODO: does only network related errors should result in
connection closure?
+ // var verr net.Error
+ // if errors.As(err, &verr) {
+ // return nil, false, verr
+ // }
+ return err
+ }
+
+ if isSelfContained {
+ // Reset the buffer to the new segment
+ // It might contain multiple frames so Read should be called
mutiple times to read all of them
+ sr.readBufferDecoded.Reset(segment)
+ return nil
+ }
+
+ frame, err := sr.readNonSelfContainedSegment(segment)
+ if err != nil {
+ return err
+ }
+
+ // Contains a single frame so we can read it all at once
+ sr.readBufferDecoded.Reset(frame)
+ return nil
+}
+
+// Non self-contained segment contains only part of a bigger frame that is
split into multiple segments.
+// Calling it results in a full frame being read into a single buffer.
+func (sr *segmentReader) readNonSelfContainedSegment(segment []byte) ([]byte,
error) {
+ frameHeader, err := readHeader(bytes.NewBuffer(segment),
sr.frameHeaderBuf[:])
+ if err != nil {
+ return nil, err
+ }
+
+ // Allocate a buffer to read the rest of the segment into
+ buf := bytes.NewBuffer(make([]byte, 0,
frameHeader.length+frameHeadSize))
+ buf.Write(segment)
+
+ // Computing how many bytes of message left to read
+ // len(segment) is the length of the first frame we already read
+ bytesToRead := frameHeader.length - len(segment) + frameHeadSize
+ err = sr.readPartialFrames(buf, bytesToRead)
+ if err != nil {
+ return nil, err
+ }
+
+ return buf.Bytes(), nil
+}
+
+// Reads parts of a bigger frame that is split into multiple segments into a
single buffer.
+// bytesToRead is the number of bytes left to read from the frame.
+// Called by readNonSelfContainedSegment.
+func (sr *segmentReader) readPartialFrames(dstBuf *bytes.Buffer, bytesToRead
int) error {
+ for bytesToRead > 0 {
+ frame, isSelfContained, err := sr.segmentCodec.decode(sr.r)
+ if err != nil {
+ return err
+ }
+ // Expected to receive only non self-contained segments
+ if isSelfContained {
+ return errUnexpectedSelfcontainedSegment
Review Comment:
The other errors rely on format
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