David K. Bainbridge | 215e024 | 2017-09-05 23:18:24 -0700 | [diff] [blame^] | 1 | // Copyright 2014 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package http2 |
| 6 | |
| 7 | import "math" |
| 8 | |
| 9 | // NewRandomWriteScheduler constructs a WriteScheduler that ignores HTTP/2 |
| 10 | // priorities. Control frames like SETTINGS and PING are written before DATA |
| 11 | // frames, but if no control frames are queued and multiple streams have queued |
| 12 | // HEADERS or DATA frames, Pop selects a ready stream arbitrarily. |
| 13 | func NewRandomWriteScheduler() WriteScheduler { |
| 14 | return &randomWriteScheduler{sq: make(map[uint32]*writeQueue)} |
| 15 | } |
| 16 | |
| 17 | type randomWriteScheduler struct { |
| 18 | // zero are frames not associated with a specific stream. |
| 19 | zero writeQueue |
| 20 | |
| 21 | // sq contains the stream-specific queues, keyed by stream ID. |
| 22 | // When a stream is idle or closed, it's deleted from the map. |
| 23 | sq map[uint32]*writeQueue |
| 24 | |
| 25 | // pool of empty queues for reuse. |
| 26 | queuePool writeQueuePool |
| 27 | } |
| 28 | |
| 29 | func (ws *randomWriteScheduler) OpenStream(streamID uint32, options OpenStreamOptions) { |
| 30 | // no-op: idle streams are not tracked |
| 31 | } |
| 32 | |
| 33 | func (ws *randomWriteScheduler) CloseStream(streamID uint32) { |
| 34 | q, ok := ws.sq[streamID] |
| 35 | if !ok { |
| 36 | return |
| 37 | } |
| 38 | delete(ws.sq, streamID) |
| 39 | ws.queuePool.put(q) |
| 40 | } |
| 41 | |
| 42 | func (ws *randomWriteScheduler) AdjustStream(streamID uint32, priority PriorityParam) { |
| 43 | // no-op: priorities are ignored |
| 44 | } |
| 45 | |
| 46 | func (ws *randomWriteScheduler) Push(wr FrameWriteRequest) { |
| 47 | id := wr.StreamID() |
| 48 | if id == 0 { |
| 49 | ws.zero.push(wr) |
| 50 | return |
| 51 | } |
| 52 | q, ok := ws.sq[id] |
| 53 | if !ok { |
| 54 | q = ws.queuePool.get() |
| 55 | ws.sq[id] = q |
| 56 | } |
| 57 | q.push(wr) |
| 58 | } |
| 59 | |
| 60 | func (ws *randomWriteScheduler) Pop() (FrameWriteRequest, bool) { |
| 61 | // Control frames first. |
| 62 | if !ws.zero.empty() { |
| 63 | return ws.zero.shift(), true |
| 64 | } |
| 65 | // Iterate over all non-idle streams until finding one that can be consumed. |
| 66 | for _, q := range ws.sq { |
| 67 | if wr, ok := q.consume(math.MaxInt32); ok { |
| 68 | return wr, true |
| 69 | } |
| 70 | } |
| 71 | return FrameWriteRequest{}, false |
| 72 | } |