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, closed, or emptied, it's deleted
23 // from the map.
24 sq map[uint32]*writeQueue
25 26 // pool of empty queues for reuse.
27 queuePool writeQueuePool
28 }
29 30 func (ws *randomWriteScheduler) OpenStream(streamID uint32, options OpenStreamOptions) {
31 // no-op: idle streams are not tracked
32 }
33 34 func (ws *randomWriteScheduler) CloseStream(streamID uint32) {
35 q, ok := ws.sq[streamID]
36 if !ok {
37 return
38 }
39 delete(ws.sq, streamID)
40 ws.queuePool.put(q)
41 }
42 43 func (ws *randomWriteScheduler) AdjustStream(streamID uint32, priority PriorityParam) {
44 // no-op: priorities are ignored
45 }
46 47 func (ws *randomWriteScheduler) Push(wr FrameWriteRequest) {
48 if wr.isControl() {
49 ws.zero.push(wr)
50 return
51 }
52 id := wr.StreamID()
53 q, ok := ws.sq[id]
54 if !ok {
55 q = ws.queuePool.get()
56 ws.sq[id] = q
57 }
58 q.push(wr)
59 }
60 61 func (ws *randomWriteScheduler) Pop() (FrameWriteRequest, bool) {
62 // Control and RST_STREAM frames first.
63 if !ws.zero.empty() {
64 return ws.zero.shift(), true
65 }
66 // Iterate over all non-idle streams until finding one that can be consumed.
67 for streamID, q := range ws.sq {
68 if wr, ok := q.consume(math.MaxInt32); ok {
69 if q.empty() {
70 delete(ws.sq, streamID)
71 ws.queuePool.put(q)
72 }
73 return wr, true
74 }
75 }
76 return FrameWriteRequest{}, false
77 }
78