joao-r-reis commented on code in PR #1946:
URL:
https://github.com/apache/cassandra-gocql-driver/pull/1946#discussion_r3273822955
##########
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 {
Review Comment:
The code in `writeFlusherImpl` has fewer loops for essentially the same
thing because as soon as the writerequest comes in the buffer is appended to a
`net.Buffers` object and the channel is appended to a `[]chan<-` object. Then
the only loop that happens is to send the result to the channels after the
write succeeds.
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