initial add - go fmt on grpc
Change-Id: Ib0afadd2fe5571d1456a091f94f5644458f7d3f4
diff --git a/vendor/google.golang.org/grpc/internal/transport/controlbuf.go b/vendor/google.golang.org/grpc/internal/transport/controlbuf.go
new file mode 100644
index 0000000..b8e0aa4
--- /dev/null
+++ b/vendor/google.golang.org/grpc/internal/transport/controlbuf.go
@@ -0,0 +1,930 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * 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 transport
+
+import (
+ "bytes"
+ "fmt"
+ "runtime"
+ "sync"
+ "sync/atomic"
+
+ "golang.org/x/net/http2"
+ "golang.org/x/net/http2/hpack"
+)
+
+var updateHeaderTblSize = func(e *hpack.Encoder, v uint32) {
+ e.SetMaxDynamicTableSizeLimit(v)
+}
+
+type itemNode struct {
+ it interface{}
+ next *itemNode
+}
+
+type itemList struct {
+ head *itemNode
+ tail *itemNode
+}
+
+func (il *itemList) enqueue(i interface{}) {
+ n := &itemNode{it: i}
+ if il.tail == nil {
+ il.head, il.tail = n, n
+ return
+ }
+ il.tail.next = n
+ il.tail = n
+}
+
+// peek returns the first item in the list without removing it from the
+// list.
+func (il *itemList) peek() interface{} {
+ return il.head.it
+}
+
+func (il *itemList) dequeue() interface{} {
+ if il.head == nil {
+ return nil
+ }
+ i := il.head.it
+ il.head = il.head.next
+ if il.head == nil {
+ il.tail = nil
+ }
+ return i
+}
+
+func (il *itemList) dequeueAll() *itemNode {
+ h := il.head
+ il.head, il.tail = nil, nil
+ return h
+}
+
+func (il *itemList) isEmpty() bool {
+ return il.head == nil
+}
+
+// The following defines various control items which could flow through
+// the control buffer of transport. They represent different aspects of
+// control tasks, e.g., flow control, settings, streaming resetting, etc.
+
+// maxQueuedTransportResponseFrames is the most queued "transport response"
+// frames we will buffer before preventing new reads from occurring on the
+// transport. These are control frames sent in response to client requests,
+// such as RST_STREAM due to bad headers or settings acks.
+const maxQueuedTransportResponseFrames = 50
+
+type cbItem interface {
+ isTransportResponseFrame() bool
+}
+
+// registerStream is used to register an incoming stream with loopy writer.
+type registerStream struct {
+ streamID uint32
+ wq *writeQuota
+}
+
+func (*registerStream) isTransportResponseFrame() bool { return false }
+
+// headerFrame is also used to register stream on the client-side.
+type headerFrame struct {
+ streamID uint32
+ hf []hpack.HeaderField
+ endStream bool // Valid on server side.
+ initStream func(uint32) (bool, error) // Used only on the client side.
+ onWrite func()
+ wq *writeQuota // write quota for the stream created.
+ cleanup *cleanupStream // Valid on the server side.
+ onOrphaned func(error) // Valid on client-side
+}
+
+func (h *headerFrame) isTransportResponseFrame() bool {
+ return h.cleanup != nil && h.cleanup.rst // Results in a RST_STREAM
+}
+
+type cleanupStream struct {
+ streamID uint32
+ rst bool
+ rstCode http2.ErrCode
+ onWrite func()
+}
+
+func (c *cleanupStream) isTransportResponseFrame() bool { return c.rst } // Results in a RST_STREAM
+
+type dataFrame struct {
+ streamID uint32
+ endStream bool
+ h []byte
+ d []byte
+ // onEachWrite is called every time
+ // a part of d is written out.
+ onEachWrite func()
+}
+
+func (*dataFrame) isTransportResponseFrame() bool { return false }
+
+type incomingWindowUpdate struct {
+ streamID uint32
+ increment uint32
+}
+
+func (*incomingWindowUpdate) isTransportResponseFrame() bool { return false }
+
+type outgoingWindowUpdate struct {
+ streamID uint32
+ increment uint32
+}
+
+func (*outgoingWindowUpdate) isTransportResponseFrame() bool {
+ return false // window updates are throttled by thresholds
+}
+
+type incomingSettings struct {
+ ss []http2.Setting
+}
+
+func (*incomingSettings) isTransportResponseFrame() bool { return true } // Results in a settings ACK
+
+type outgoingSettings struct {
+ ss []http2.Setting
+}
+
+func (*outgoingSettings) isTransportResponseFrame() bool { return false }
+
+type incomingGoAway struct {
+}
+
+func (*incomingGoAway) isTransportResponseFrame() bool { return false }
+
+type goAway struct {
+ code http2.ErrCode
+ debugData []byte
+ headsUp bool
+ closeConn bool
+}
+
+func (*goAway) isTransportResponseFrame() bool { return false }
+
+type ping struct {
+ ack bool
+ data [8]byte
+}
+
+func (*ping) isTransportResponseFrame() bool { return true }
+
+type outFlowControlSizeRequest struct {
+ resp chan uint32
+}
+
+func (*outFlowControlSizeRequest) isTransportResponseFrame() bool { return false }
+
+type outStreamState int
+
+const (
+ active outStreamState = iota
+ empty
+ waitingOnStreamQuota
+)
+
+type outStream struct {
+ id uint32
+ state outStreamState
+ itl *itemList
+ bytesOutStanding int
+ wq *writeQuota
+
+ next *outStream
+ prev *outStream
+}
+
+func (s *outStream) deleteSelf() {
+ if s.prev != nil {
+ s.prev.next = s.next
+ }
+ if s.next != nil {
+ s.next.prev = s.prev
+ }
+ s.next, s.prev = nil, nil
+}
+
+type outStreamList struct {
+ // Following are sentinel objects that mark the
+ // beginning and end of the list. They do not
+ // contain any item lists. All valid objects are
+ // inserted in between them.
+ // This is needed so that an outStream object can
+ // deleteSelf() in O(1) time without knowing which
+ // list it belongs to.
+ head *outStream
+ tail *outStream
+}
+
+func newOutStreamList() *outStreamList {
+ head, tail := new(outStream), new(outStream)
+ head.next = tail
+ tail.prev = head
+ return &outStreamList{
+ head: head,
+ tail: tail,
+ }
+}
+
+func (l *outStreamList) enqueue(s *outStream) {
+ e := l.tail.prev
+ e.next = s
+ s.prev = e
+ s.next = l.tail
+ l.tail.prev = s
+}
+
+// remove from the beginning of the list.
+func (l *outStreamList) dequeue() *outStream {
+ b := l.head.next
+ if b == l.tail {
+ return nil
+ }
+ b.deleteSelf()
+ return b
+}
+
+// controlBuffer is a way to pass information to loopy.
+// Information is passed as specific struct types called control frames.
+// A control frame not only represents data, messages or headers to be sent out
+// but can also be used to instruct loopy to update its internal state.
+// It shouldn't be confused with an HTTP2 frame, although some of the control frames
+// like dataFrame and headerFrame do go out on wire as HTTP2 frames.
+type controlBuffer struct {
+ ch chan struct{}
+ done <-chan struct{}
+ mu sync.Mutex
+ consumerWaiting bool
+ list *itemList
+ err error
+
+ // transportResponseFrames counts the number of queued items that represent
+ // the response of an action initiated by the peer. trfChan is created
+ // when transportResponseFrames >= maxQueuedTransportResponseFrames and is
+ // closed and nilled when transportResponseFrames drops below the
+ // threshold. Both fields are protected by mu.
+ transportResponseFrames int
+ trfChan atomic.Value // *chan struct{}
+}
+
+func newControlBuffer(done <-chan struct{}) *controlBuffer {
+ return &controlBuffer{
+ ch: make(chan struct{}, 1),
+ list: &itemList{},
+ done: done,
+ }
+}
+
+// throttle blocks if there are too many incomingSettings/cleanupStreams in the
+// controlbuf.
+func (c *controlBuffer) throttle() {
+ ch, _ := c.trfChan.Load().(*chan struct{})
+ if ch != nil {
+ select {
+ case <-*ch:
+ case <-c.done:
+ }
+ }
+}
+
+func (c *controlBuffer) put(it cbItem) error {
+ _, err := c.executeAndPut(nil, it)
+ return err
+}
+
+func (c *controlBuffer) executeAndPut(f func(it interface{}) bool, it cbItem) (bool, error) {
+ var wakeUp bool
+ c.mu.Lock()
+ if c.err != nil {
+ c.mu.Unlock()
+ return false, c.err
+ }
+ if f != nil {
+ if !f(it) { // f wasn't successful
+ c.mu.Unlock()
+ return false, nil
+ }
+ }
+ if c.consumerWaiting {
+ wakeUp = true
+ c.consumerWaiting = false
+ }
+ c.list.enqueue(it)
+ if it.isTransportResponseFrame() {
+ c.transportResponseFrames++
+ if c.transportResponseFrames == maxQueuedTransportResponseFrames {
+ // We are adding the frame that puts us over the threshold; create
+ // a throttling channel.
+ ch := make(chan struct{})
+ c.trfChan.Store(&ch)
+ }
+ }
+ c.mu.Unlock()
+ if wakeUp {
+ select {
+ case c.ch <- struct{}{}:
+ default:
+ }
+ }
+ return true, nil
+}
+
+// Note argument f should never be nil.
+func (c *controlBuffer) execute(f func(it interface{}) bool, it interface{}) (bool, error) {
+ c.mu.Lock()
+ if c.err != nil {
+ c.mu.Unlock()
+ return false, c.err
+ }
+ if !f(it) { // f wasn't successful
+ c.mu.Unlock()
+ return false, nil
+ }
+ c.mu.Unlock()
+ return true, nil
+}
+
+func (c *controlBuffer) get(block bool) (interface{}, error) {
+ for {
+ c.mu.Lock()
+ if c.err != nil {
+ c.mu.Unlock()
+ return nil, c.err
+ }
+ if !c.list.isEmpty() {
+ h := c.list.dequeue().(cbItem)
+ if h.isTransportResponseFrame() {
+ if c.transportResponseFrames == maxQueuedTransportResponseFrames {
+ // We are removing the frame that put us over the
+ // threshold; close and clear the throttling channel.
+ ch := c.trfChan.Load().(*chan struct{})
+ close(*ch)
+ c.trfChan.Store((*chan struct{})(nil))
+ }
+ c.transportResponseFrames--
+ }
+ c.mu.Unlock()
+ return h, nil
+ }
+ if !block {
+ c.mu.Unlock()
+ return nil, nil
+ }
+ c.consumerWaiting = true
+ c.mu.Unlock()
+ select {
+ case <-c.ch:
+ case <-c.done:
+ c.finish()
+ return nil, ErrConnClosing
+ }
+ }
+}
+
+func (c *controlBuffer) finish() {
+ c.mu.Lock()
+ if c.err != nil {
+ c.mu.Unlock()
+ return
+ }
+ c.err = ErrConnClosing
+ // There may be headers for streams in the control buffer.
+ // These streams need to be cleaned out since the transport
+ // is still not aware of these yet.
+ for head := c.list.dequeueAll(); head != nil; head = head.next {
+ hdr, ok := head.it.(*headerFrame)
+ if !ok {
+ continue
+ }
+ if hdr.onOrphaned != nil { // It will be nil on the server-side.
+ hdr.onOrphaned(ErrConnClosing)
+ }
+ }
+ c.mu.Unlock()
+}
+
+type side int
+
+const (
+ clientSide side = iota
+ serverSide
+)
+
+// Loopy receives frames from the control buffer.
+// Each frame is handled individually; most of the work done by loopy goes
+// into handling data frames. Loopy maintains a queue of active streams, and each
+// stream maintains a queue of data frames; as loopy receives data frames
+// it gets added to the queue of the relevant stream.
+// Loopy goes over this list of active streams by processing one node every iteration,
+// thereby closely resemebling to a round-robin scheduling over all streams. While
+// processing a stream, loopy writes out data bytes from this stream capped by the min
+// of http2MaxFrameLen, connection-level flow control and stream-level flow control.
+type loopyWriter struct {
+ side side
+ cbuf *controlBuffer
+ sendQuota uint32
+ oiws uint32 // outbound initial window size.
+ // estdStreams is map of all established streams that are not cleaned-up yet.
+ // On client-side, this is all streams whose headers were sent out.
+ // On server-side, this is all streams whose headers were received.
+ estdStreams map[uint32]*outStream // Established streams.
+ // activeStreams is a linked-list of all streams that have data to send and some
+ // stream-level flow control quota.
+ // Each of these streams internally have a list of data items(and perhaps trailers
+ // on the server-side) to be sent out.
+ activeStreams *outStreamList
+ framer *framer
+ hBuf *bytes.Buffer // The buffer for HPACK encoding.
+ hEnc *hpack.Encoder // HPACK encoder.
+ bdpEst *bdpEstimator
+ draining bool
+
+ // Side-specific handlers
+ ssGoAwayHandler func(*goAway) (bool, error)
+}
+
+func newLoopyWriter(s side, fr *framer, cbuf *controlBuffer, bdpEst *bdpEstimator) *loopyWriter {
+ var buf bytes.Buffer
+ l := &loopyWriter{
+ side: s,
+ cbuf: cbuf,
+ sendQuota: defaultWindowSize,
+ oiws: defaultWindowSize,
+ estdStreams: make(map[uint32]*outStream),
+ activeStreams: newOutStreamList(),
+ framer: fr,
+ hBuf: &buf,
+ hEnc: hpack.NewEncoder(&buf),
+ bdpEst: bdpEst,
+ }
+ return l
+}
+
+const minBatchSize = 1000
+
+// run should be run in a separate goroutine.
+// It reads control frames from controlBuf and processes them by:
+// 1. Updating loopy's internal state, or/and
+// 2. Writing out HTTP2 frames on the wire.
+//
+// Loopy keeps all active streams with data to send in a linked-list.
+// All streams in the activeStreams linked-list must have both:
+// 1. Data to send, and
+// 2. Stream level flow control quota available.
+//
+// In each iteration of run loop, other than processing the incoming control
+// frame, loopy calls processData, which processes one node from the activeStreams linked-list.
+// This results in writing of HTTP2 frames into an underlying write buffer.
+// When there's no more control frames to read from controlBuf, loopy flushes the write buffer.
+// As an optimization, to increase the batch size for each flush, loopy yields the processor, once
+// if the batch size is too low to give stream goroutines a chance to fill it up.
+func (l *loopyWriter) run() (err error) {
+ defer func() {
+ if err == ErrConnClosing {
+ // Don't log ErrConnClosing as error since it happens
+ // 1. When the connection is closed by some other known issue.
+ // 2. User closed the connection.
+ // 3. A graceful close of connection.
+ infof("transport: loopyWriter.run returning. %v", err)
+ err = nil
+ }
+ }()
+ for {
+ it, err := l.cbuf.get(true)
+ if err != nil {
+ return err
+ }
+ if err = l.handle(it); err != nil {
+ return err
+ }
+ if _, err = l.processData(); err != nil {
+ return err
+ }
+ gosched := true
+ hasdata:
+ for {
+ it, err := l.cbuf.get(false)
+ if err != nil {
+ return err
+ }
+ if it != nil {
+ if err = l.handle(it); err != nil {
+ return err
+ }
+ if _, err = l.processData(); err != nil {
+ return err
+ }
+ continue hasdata
+ }
+ isEmpty, err := l.processData()
+ if err != nil {
+ return err
+ }
+ if !isEmpty {
+ continue hasdata
+ }
+ if gosched {
+ gosched = false
+ if l.framer.writer.offset < minBatchSize {
+ runtime.Gosched()
+ continue hasdata
+ }
+ }
+ l.framer.writer.Flush()
+ break hasdata
+
+ }
+ }
+}
+
+func (l *loopyWriter) outgoingWindowUpdateHandler(w *outgoingWindowUpdate) error {
+ return l.framer.fr.WriteWindowUpdate(w.streamID, w.increment)
+}
+
+func (l *loopyWriter) incomingWindowUpdateHandler(w *incomingWindowUpdate) error {
+ // Otherwise update the quota.
+ if w.streamID == 0 {
+ l.sendQuota += w.increment
+ return nil
+ }
+ // Find the stream and update it.
+ if str, ok := l.estdStreams[w.streamID]; ok {
+ str.bytesOutStanding -= int(w.increment)
+ if strQuota := int(l.oiws) - str.bytesOutStanding; strQuota > 0 && str.state == waitingOnStreamQuota {
+ str.state = active
+ l.activeStreams.enqueue(str)
+ return nil
+ }
+ }
+ return nil
+}
+
+func (l *loopyWriter) outgoingSettingsHandler(s *outgoingSettings) error {
+ return l.framer.fr.WriteSettings(s.ss...)
+}
+
+func (l *loopyWriter) incomingSettingsHandler(s *incomingSettings) error {
+ if err := l.applySettings(s.ss); err != nil {
+ return err
+ }
+ return l.framer.fr.WriteSettingsAck()
+}
+
+func (l *loopyWriter) registerStreamHandler(h *registerStream) error {
+ str := &outStream{
+ id: h.streamID,
+ state: empty,
+ itl: &itemList{},
+ wq: h.wq,
+ }
+ l.estdStreams[h.streamID] = str
+ return nil
+}
+
+func (l *loopyWriter) headerHandler(h *headerFrame) error {
+ if l.side == serverSide {
+ str, ok := l.estdStreams[h.streamID]
+ if !ok {
+ warningf("transport: loopy doesn't recognize the stream: %d", h.streamID)
+ return nil
+ }
+ // Case 1.A: Server is responding back with headers.
+ if !h.endStream {
+ return l.writeHeader(h.streamID, h.endStream, h.hf, h.onWrite)
+ }
+ // else: Case 1.B: Server wants to close stream.
+
+ if str.state != empty { // either active or waiting on stream quota.
+ // add it str's list of items.
+ str.itl.enqueue(h)
+ return nil
+ }
+ if err := l.writeHeader(h.streamID, h.endStream, h.hf, h.onWrite); err != nil {
+ return err
+ }
+ return l.cleanupStreamHandler(h.cleanup)
+ }
+ // Case 2: Client wants to originate stream.
+ str := &outStream{
+ id: h.streamID,
+ state: empty,
+ itl: &itemList{},
+ wq: h.wq,
+ }
+ str.itl.enqueue(h)
+ return l.originateStream(str)
+}
+
+func (l *loopyWriter) originateStream(str *outStream) error {
+ hdr := str.itl.dequeue().(*headerFrame)
+ sendPing, err := hdr.initStream(str.id)
+ if err != nil {
+ if err == ErrConnClosing {
+ return err
+ }
+ // Other errors(errStreamDrain) need not close transport.
+ return nil
+ }
+ if err = l.writeHeader(str.id, hdr.endStream, hdr.hf, hdr.onWrite); err != nil {
+ return err
+ }
+ l.estdStreams[str.id] = str
+ if sendPing {
+ return l.pingHandler(&ping{data: [8]byte{}})
+ }
+ return nil
+}
+
+func (l *loopyWriter) writeHeader(streamID uint32, endStream bool, hf []hpack.HeaderField, onWrite func()) error {
+ if onWrite != nil {
+ onWrite()
+ }
+ l.hBuf.Reset()
+ for _, f := range hf {
+ if err := l.hEnc.WriteField(f); err != nil {
+ warningf("transport: loopyWriter.writeHeader encountered error while encoding headers:", err)
+ }
+ }
+ var (
+ err error
+ endHeaders, first bool
+ )
+ first = true
+ for !endHeaders {
+ size := l.hBuf.Len()
+ if size > http2MaxFrameLen {
+ size = http2MaxFrameLen
+ } else {
+ endHeaders = true
+ }
+ if first {
+ first = false
+ err = l.framer.fr.WriteHeaders(http2.HeadersFrameParam{
+ StreamID: streamID,
+ BlockFragment: l.hBuf.Next(size),
+ EndStream: endStream,
+ EndHeaders: endHeaders,
+ })
+ } else {
+ err = l.framer.fr.WriteContinuation(
+ streamID,
+ endHeaders,
+ l.hBuf.Next(size),
+ )
+ }
+ if err != nil {
+ return err
+ }
+ }
+ return nil
+}
+
+func (l *loopyWriter) preprocessData(df *dataFrame) error {
+ str, ok := l.estdStreams[df.streamID]
+ if !ok {
+ return nil
+ }
+ // If we got data for a stream it means that
+ // stream was originated and the headers were sent out.
+ str.itl.enqueue(df)
+ if str.state == empty {
+ str.state = active
+ l.activeStreams.enqueue(str)
+ }
+ return nil
+}
+
+func (l *loopyWriter) pingHandler(p *ping) error {
+ if !p.ack {
+ l.bdpEst.timesnap(p.data)
+ }
+ return l.framer.fr.WritePing(p.ack, p.data)
+
+}
+
+func (l *loopyWriter) outFlowControlSizeRequestHandler(o *outFlowControlSizeRequest) error {
+ o.resp <- l.sendQuota
+ return nil
+}
+
+func (l *loopyWriter) cleanupStreamHandler(c *cleanupStream) error {
+ c.onWrite()
+ if str, ok := l.estdStreams[c.streamID]; ok {
+ // On the server side it could be a trailers-only response or
+ // a RST_STREAM before stream initialization thus the stream might
+ // not be established yet.
+ delete(l.estdStreams, c.streamID)
+ str.deleteSelf()
+ }
+ if c.rst { // If RST_STREAM needs to be sent.
+ if err := l.framer.fr.WriteRSTStream(c.streamID, c.rstCode); err != nil {
+ return err
+ }
+ }
+ if l.side == clientSide && l.draining && len(l.estdStreams) == 0 {
+ return ErrConnClosing
+ }
+ return nil
+}
+
+func (l *loopyWriter) incomingGoAwayHandler(*incomingGoAway) error {
+ if l.side == clientSide {
+ l.draining = true
+ if len(l.estdStreams) == 0 {
+ return ErrConnClosing
+ }
+ }
+ return nil
+}
+
+func (l *loopyWriter) goAwayHandler(g *goAway) error {
+ // Handling of outgoing GoAway is very specific to side.
+ if l.ssGoAwayHandler != nil {
+ draining, err := l.ssGoAwayHandler(g)
+ if err != nil {
+ return err
+ }
+ l.draining = draining
+ }
+ return nil
+}
+
+func (l *loopyWriter) handle(i interface{}) error {
+ switch i := i.(type) {
+ case *incomingWindowUpdate:
+ return l.incomingWindowUpdateHandler(i)
+ case *outgoingWindowUpdate:
+ return l.outgoingWindowUpdateHandler(i)
+ case *incomingSettings:
+ return l.incomingSettingsHandler(i)
+ case *outgoingSettings:
+ return l.outgoingSettingsHandler(i)
+ case *headerFrame:
+ return l.headerHandler(i)
+ case *registerStream:
+ return l.registerStreamHandler(i)
+ case *cleanupStream:
+ return l.cleanupStreamHandler(i)
+ case *incomingGoAway:
+ return l.incomingGoAwayHandler(i)
+ case *dataFrame:
+ return l.preprocessData(i)
+ case *ping:
+ return l.pingHandler(i)
+ case *goAway:
+ return l.goAwayHandler(i)
+ case *outFlowControlSizeRequest:
+ return l.outFlowControlSizeRequestHandler(i)
+ default:
+ return fmt.Errorf("transport: unknown control message type %T", i)
+ }
+}
+
+func (l *loopyWriter) applySettings(ss []http2.Setting) error {
+ for _, s := range ss {
+ switch s.ID {
+ case http2.SettingInitialWindowSize:
+ o := l.oiws
+ l.oiws = s.Val
+ if o < l.oiws {
+ // If the new limit is greater make all depleted streams active.
+ for _, stream := range l.estdStreams {
+ if stream.state == waitingOnStreamQuota {
+ stream.state = active
+ l.activeStreams.enqueue(stream)
+ }
+ }
+ }
+ case http2.SettingHeaderTableSize:
+ updateHeaderTblSize(l.hEnc, s.Val)
+ }
+ }
+ return nil
+}
+
+// processData removes the first stream from active streams, writes out at most 16KB
+// of its data and then puts it at the end of activeStreams if there's still more data
+// to be sent and stream has some stream-level flow control.
+func (l *loopyWriter) processData() (bool, error) {
+ if l.sendQuota == 0 {
+ return true, nil
+ }
+ str := l.activeStreams.dequeue() // Remove the first stream.
+ if str == nil {
+ return true, nil
+ }
+ dataItem := str.itl.peek().(*dataFrame) // Peek at the first data item this stream.
+ // A data item is represented by a dataFrame, since it later translates into
+ // multiple HTTP2 data frames.
+ // Every dataFrame has two buffers; h that keeps grpc-message header and d that is acutal data.
+ // As an optimization to keep wire traffic low, data from d is copied to h to make as big as the
+ // maximum possilbe HTTP2 frame size.
+
+ if len(dataItem.h) == 0 && len(dataItem.d) == 0 { // Empty data frame
+ // Client sends out empty data frame with endStream = true
+ if err := l.framer.fr.WriteData(dataItem.streamID, dataItem.endStream, nil); err != nil {
+ return false, err
+ }
+ str.itl.dequeue() // remove the empty data item from stream
+ if str.itl.isEmpty() {
+ str.state = empty
+ } else if trailer, ok := str.itl.peek().(*headerFrame); ok { // the next item is trailers.
+ if err := l.writeHeader(trailer.streamID, trailer.endStream, trailer.hf, trailer.onWrite); err != nil {
+ return false, err
+ }
+ if err := l.cleanupStreamHandler(trailer.cleanup); err != nil {
+ return false, nil
+ }
+ } else {
+ l.activeStreams.enqueue(str)
+ }
+ return false, nil
+ }
+ var (
+ idx int
+ buf []byte
+ )
+ if len(dataItem.h) != 0 { // data header has not been written out yet.
+ buf = dataItem.h
+ } else {
+ idx = 1
+ buf = dataItem.d
+ }
+ size := http2MaxFrameLen
+ if len(buf) < size {
+ size = len(buf)
+ }
+ if strQuota := int(l.oiws) - str.bytesOutStanding; strQuota <= 0 { // stream-level flow control.
+ str.state = waitingOnStreamQuota
+ return false, nil
+ } else if strQuota < size {
+ size = strQuota
+ }
+
+ if l.sendQuota < uint32(size) { // connection-level flow control.
+ size = int(l.sendQuota)
+ }
+ // Now that outgoing flow controls are checked we can replenish str's write quota
+ str.wq.replenish(size)
+ var endStream bool
+ // If this is the last data message on this stream and all of it can be written in this iteration.
+ if dataItem.endStream && size == len(buf) {
+ // buf contains either data or it contains header but data is empty.
+ if idx == 1 || len(dataItem.d) == 0 {
+ endStream = true
+ }
+ }
+ if dataItem.onEachWrite != nil {
+ dataItem.onEachWrite()
+ }
+ if err := l.framer.fr.WriteData(dataItem.streamID, endStream, buf[:size]); err != nil {
+ return false, err
+ }
+ buf = buf[size:]
+ str.bytesOutStanding += size
+ l.sendQuota -= uint32(size)
+ if idx == 0 {
+ dataItem.h = buf
+ } else {
+ dataItem.d = buf
+ }
+
+ if len(dataItem.h) == 0 && len(dataItem.d) == 0 { // All the data from that message was written out.
+ str.itl.dequeue()
+ }
+ if str.itl.isEmpty() {
+ str.state = empty
+ } else if trailer, ok := str.itl.peek().(*headerFrame); ok { // The next item is trailers.
+ if err := l.writeHeader(trailer.streamID, trailer.endStream, trailer.hf, trailer.onWrite); err != nil {
+ return false, err
+ }
+ if err := l.cleanupStreamHandler(trailer.cleanup); err != nil {
+ return false, err
+ }
+ } else if int(l.oiws)-str.bytesOutStanding <= 0 { // Ran out of stream quota.
+ str.state = waitingOnStreamQuota
+ } else { // Otherwise add it back to the list of active streams.
+ l.activeStreams.enqueue(str)
+ }
+ return false, nil
+}