diff options
Diffstat (limited to 'vendor/golang.org/x/net/http2/writesched.go')
| -rw-r--r-- | vendor/golang.org/x/net/http2/writesched.go | 410 |
1 files changed, 175 insertions, 235 deletions
diff --git a/vendor/golang.org/x/net/http2/writesched.go b/vendor/golang.org/x/net/http2/writesched.go index c24316c..9f3e1b3 100644 --- a/vendor/golang.org/x/net/http2/writesched.go +++ b/vendor/golang.org/x/net/http2/writesched.go @@ -6,14 +6,51 @@ package http2 import "fmt" -// frameWriteMsg is a request to write a frame. -type frameWriteMsg struct { +// WriteScheduler is the interface implemented by HTTP/2 write schedulers. +// Methods are never called concurrently. +type WriteScheduler interface { + // OpenStream opens a new stream in the write scheduler. + // It is illegal to call this with streamID=0 or with a streamID that is + // already open -- the call may panic. + OpenStream(streamID uint32, options OpenStreamOptions) + + // CloseStream closes a stream in the write scheduler. Any frames queued on + // this stream should be discarded. It is illegal to call this on a stream + // that is not open -- the call may panic. + CloseStream(streamID uint32) + + // AdjustStream adjusts the priority of the given stream. This may be called + // on a stream that has not yet been opened or has been closed. Note that + // RFC 7540 allows PRIORITY frames to be sent on streams in any state. See: + // https://tools.ietf.org/html/rfc7540#section-5.1 + AdjustStream(streamID uint32, priority PriorityParam) + + // Push queues a frame in the scheduler. + Push(wr FrameWriteRequest) + + // Pop dequeues the next frame to write. Returns false if no frames can + // be written. Frames with a given wr.StreamID() are Pop'd in the same + // order they are Push'd. + Pop() (wr FrameWriteRequest, ok bool) +} + +// OpenStreamOptions specifies extra options for WriteScheduler.OpenStream. +type OpenStreamOptions struct { + // PusherID is zero if the stream was initiated by the client. Otherwise, + // PusherID names the stream that pushed the newly opened stream. + PusherID uint32 +} + +// FrameWriteRequest is a request to write a frame. +type FrameWriteRequest struct { // write is the interface value that does the writing, once the - // writeScheduler (below) has decided to select this frame - // to write. The write functions are all defined in write.go. + // WriteScheduler has selected this frame to write. The write + // functions are all defined in write.go. write writeFramer - stream *stream // used for prioritization. nil for non-stream frames. + // stream is the stream on which this frame will be written. + // nil for non-stream frames like PING and SETTINGS. + stream *stream // done, if non-nil, must be a buffered channel with space for // 1 message and is sent the return value from write (or an @@ -21,263 +58,166 @@ type frameWriteMsg struct { done chan error } -// for debugging only: -func (wm frameWriteMsg) String() string { - var streamID uint32 - if wm.stream != nil { - streamID = wm.stream.id - } - var des string - if s, ok := wm.write.(fmt.Stringer); ok { - des = s.String() - } else { - des = fmt.Sprintf("%T", wm.write) - } - return fmt.Sprintf("[frameWriteMsg stream=%d, ch=%v, type: %v]", streamID, wm.done != nil, des) -} - -// writeScheduler tracks pending frames to write, priorities, and decides -// the next one to use. It is not thread-safe. -type writeScheduler struct { - // zero are frames not associated with a specific stream. - // They're sent before any stream-specific freams. - zero writeQueue - - // maxFrameSize is the maximum size of a DATA frame - // we'll write. Must be non-zero and between 16K-16M. - maxFrameSize uint32 - - // sq contains the stream-specific queues, keyed by stream ID. - // when a stream is idle, it's deleted from the map. - sq map[uint32]*writeQueue - - // canSend is a slice of memory that's reused between frame - // scheduling decisions to hold the list of writeQueues (from sq) - // which have enough flow control data to send. After canSend is - // built, the best is selected. - canSend []*writeQueue - - // pool of empty queues for reuse. - queuePool []*writeQueue -} - -func (ws *writeScheduler) putEmptyQueue(q *writeQueue) { - if len(q.s) != 0 { - panic("queue must be empty") - } - ws.queuePool = append(ws.queuePool, q) -} - -func (ws *writeScheduler) getEmptyQueue() *writeQueue { - ln := len(ws.queuePool) - if ln == 0 { - return new(writeQueue) - } - q := ws.queuePool[ln-1] - ws.queuePool = ws.queuePool[:ln-1] - return q -} - -func (ws *writeScheduler) empty() bool { return ws.zero.empty() && len(ws.sq) == 0 } - -func (ws *writeScheduler) add(wm frameWriteMsg) { - st := wm.stream - if st == nil { - ws.zero.push(wm) - } else { - ws.streamQueue(st.id).push(wm) - } -} - -func (ws *writeScheduler) streamQueue(streamID uint32) *writeQueue { - if q, ok := ws.sq[streamID]; ok { - return q - } - if ws.sq == nil { - ws.sq = make(map[uint32]*writeQueue) - } - q := ws.getEmptyQueue() - ws.sq[streamID] = q - return q -} - -// take returns the most important frame to write and removes it from the scheduler. -// It is illegal to call this if the scheduler is empty or if there are no connection-level -// flow control bytes available. -func (ws *writeScheduler) take() (wm frameWriteMsg, ok bool) { - if ws.maxFrameSize == 0 { - panic("internal error: ws.maxFrameSize not initialized or invalid") - } - - // If there any frames not associated with streams, prefer those first. - // These are usually SETTINGS, etc. - if !ws.zero.empty() { - return ws.zero.shift(), true - } - if len(ws.sq) == 0 { - return - } - - // Next, prioritize frames on streams that aren't DATA frames (no cost). - for id, q := range ws.sq { - if q.firstIsNoCost() { - return ws.takeFrom(id, q) - } - } - - // Now, all that remains are DATA frames with non-zero bytes to - // send. So pick the best one. - if len(ws.canSend) != 0 { - panic("should be empty") - } - for _, q := range ws.sq { - if n := ws.streamWritableBytes(q); n > 0 { - ws.canSend = append(ws.canSend, q) - } - } - if len(ws.canSend) == 0 { - return - } - defer ws.zeroCanSend() - - // TODO: find the best queue - q := ws.canSend[0] - - return ws.takeFrom(q.streamID(), q) -} - -// zeroCanSend is defered from take. -func (ws *writeScheduler) zeroCanSend() { - for i := range ws.canSend { - ws.canSend[i] = nil - } - ws.canSend = ws.canSend[:0] -} - -// streamWritableBytes returns the number of DATA bytes we could write -// from the given queue's stream, if this stream/queue were -// selected. It is an error to call this if q's head isn't a -// *writeData. -func (ws *writeScheduler) streamWritableBytes(q *writeQueue) int32 { - wm := q.head() - ret := wm.stream.flow.available() // max we can write - if ret == 0 { +// StreamID returns the id of the stream this frame will be written to. +// 0 is used for non-stream frames such as PING and SETTINGS. +func (wr FrameWriteRequest) StreamID() uint32 { + if wr.stream == nil { return 0 } - if int32(ws.maxFrameSize) < ret { - ret = int32(ws.maxFrameSize) - } - if ret == 0 { - panic("internal error: ws.maxFrameSize not initialized or invalid") - } - wd := wm.write.(*writeData) - if len(wd.p) < int(ret) { - ret = int32(len(wd.p)) - } - return ret -} - -func (ws *writeScheduler) takeFrom(id uint32, q *writeQueue) (wm frameWriteMsg, ok bool) { - wm = q.head() - // If the first item in this queue costs flow control tokens - // and we don't have enough, write as much as we can. - if wd, ok := wm.write.(*writeData); ok && len(wd.p) > 0 { - allowed := wm.stream.flow.available() // max we can write - if allowed == 0 { - // No quota available. Caller can try the next stream. - return frameWriteMsg{}, false + return wr.stream.id +} + +// DataSize returns the number of flow control bytes that must be consumed +// to write this entire frame. This is 0 for non-DATA frames. +func (wr FrameWriteRequest) DataSize() int { + if wd, ok := wr.write.(*writeData); ok { + return len(wd.p) + } + return 0 +} + +// Consume consumes min(n, available) bytes from this frame, where available +// is the number of flow control bytes available on the stream. Consume returns +// 0, 1, or 2 frames, where the integer return value gives the number of frames +// returned. +// +// If flow control prevents consuming any bytes, this returns (_, _, 0). If +// the entire frame was consumed, this returns (wr, _, 1). Otherwise, this +// returns (consumed, rest, 2), where 'consumed' contains the consumed bytes and +// 'rest' contains the remaining bytes. The consumed bytes are deducted from the +// underlying stream's flow control budget. +func (wr FrameWriteRequest) Consume(n int32) (FrameWriteRequest, FrameWriteRequest, int) { + var empty FrameWriteRequest + + // Non-DATA frames are always consumed whole. + wd, ok := wr.write.(*writeData) + if !ok || len(wd.p) == 0 { + return wr, empty, 1 + } + + // Might need to split after applying limits. + allowed := wr.stream.flow.available() + if n < allowed { + allowed = n + } + if wr.stream.sc.maxFrameSize < allowed { + allowed = wr.stream.sc.maxFrameSize + } + if allowed <= 0 { + return empty, empty, 0 + } + if len(wd.p) > int(allowed) { + wr.stream.flow.take(allowed) + consumed := FrameWriteRequest{ + stream: wr.stream, + write: &writeData{ + streamID: wd.streamID, + p: wd.p[:allowed], + // Even if the original had endStream set, there + // are bytes remaining because len(wd.p) > allowed, + // so we know endStream is false. + endStream: false, + }, + // Our caller is blocking on the final DATA frame, not + // this intermediate frame, so no need to wait. + done: nil, } - if int32(ws.maxFrameSize) < allowed { - allowed = int32(ws.maxFrameSize) - } - // TODO: further restrict the allowed size, because even if - // the peer says it's okay to write 16MB data frames, we might - // want to write smaller ones to properly weight competing - // streams' priorities. - - if len(wd.p) > int(allowed) { - wm.stream.flow.take(allowed) - chunk := wd.p[:allowed] - wd.p = wd.p[allowed:] - // Make up a new write message of a valid size, rather - // than shifting one off the queue. - return frameWriteMsg{ - stream: wm.stream, - write: &writeData{ - streamID: wd.streamID, - p: chunk, - // even if the original had endStream set, there - // arebytes remaining because len(wd.p) > allowed, - // so we know endStream is false: - endStream: false, - }, - // our caller is blocking on the final DATA frame, not - // these intermediates, so no need to wait: - done: nil, - }, true + rest := FrameWriteRequest{ + stream: wr.stream, + write: &writeData{ + streamID: wd.streamID, + p: wd.p[allowed:], + endStream: wd.endStream, + }, + done: wr.done, } - wm.stream.flow.take(int32(len(wd.p))) + return consumed, rest, 2 } - q.shift() - if q.empty() { - ws.putEmptyQueue(q) - delete(ws.sq, id) - } - return wm, true + // The frame is consumed whole. + // NB: This cast cannot overflow because allowed is <= math.MaxInt32. + wr.stream.flow.take(int32(len(wd.p))) + return wr, empty, 1 } -func (ws *writeScheduler) forgetStream(id uint32) { - q, ok := ws.sq[id] - if !ok { - return +// String is for debugging only. +func (wr FrameWriteRequest) String() string { + var streamID uint32 + if wr.stream != nil { + streamID = wr.stream.id } - delete(ws.sq, id) - - // But keep it for others later. - for i := range q.s { - q.s[i] = frameWriteMsg{} + var des string + if s, ok := wr.write.(fmt.Stringer); ok { + des = s.String() + } else { + des = fmt.Sprintf("%T", wr.write) } - q.s = q.s[:0] - ws.putEmptyQueue(q) + return fmt.Sprintf("[FrameWriteRequest stream=%d, ch=%v, writer=%v]", streamID, wr.done != nil, des) } +// writeQueue is used by implementations of WriteScheduler. type writeQueue struct { - s []frameWriteMsg + s []FrameWriteRequest } -// streamID returns the stream ID for a non-empty stream-specific queue. -func (q *writeQueue) streamID() uint32 { return q.s[0].stream.id } - func (q *writeQueue) empty() bool { return len(q.s) == 0 } -func (q *writeQueue) push(wm frameWriteMsg) { - q.s = append(q.s, wm) +func (q *writeQueue) push(wr FrameWriteRequest) { + q.s = append(q.s, wr) } -// head returns the next item that would be removed by shift. -func (q *writeQueue) head() frameWriteMsg { +func (q *writeQueue) shift() FrameWriteRequest { if len(q.s) == 0 { panic("invalid use of queue") } - return q.s[0] + wr := q.s[0] + // TODO: less copy-happy queue. + copy(q.s, q.s[1:]) + q.s[len(q.s)-1] = FrameWriteRequest{} + q.s = q.s[:len(q.s)-1] + return wr } -func (q *writeQueue) shift() frameWriteMsg { +// consume consumes up to n bytes from q.s[0]. If the frame is +// entirely consumed, it is removed from the queue. If the frame +// is partially consumed, the frame is kept with the consumed +// bytes removed. Returns true iff any bytes were consumed. +func (q *writeQueue) consume(n int32) (FrameWriteRequest, bool) { if len(q.s) == 0 { - panic("invalid use of queue") + return FrameWriteRequest{}, false } - wm := q.s[0] - // TODO: less copy-happy queue. - copy(q.s, q.s[1:]) - q.s[len(q.s)-1] = frameWriteMsg{} - q.s = q.s[:len(q.s)-1] - return wm + consumed, rest, numresult := q.s[0].Consume(n) + switch numresult { + case 0: + return FrameWriteRequest{}, false + case 1: + q.shift() + case 2: + q.s[0] = rest + } + return consumed, true +} + +type writeQueuePool []*writeQueue + +// put inserts an unused writeQueue into the pool. +func (p *writeQueuePool) put(q *writeQueue) { + for i := range q.s { + q.s[i] = FrameWriteRequest{} + } + q.s = q.s[:0] + *p = append(*p, q) } -func (q *writeQueue) firstIsNoCost() bool { - if df, ok := q.s[0].write.(*writeData); ok { - return len(df.p) == 0 +// get returns an empty writeQueue. +func (p *writeQueuePool) get() *writeQueue { + ln := len(*p) + if ln == 0 { + return new(writeQueue) } - return true + x := ln - 1 + q := (*p)[x] + (*p)[x] = nil + *p = (*p)[:x] + return q } |