1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
/*
*
* Copyright 2014, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
package transport
import (
"fmt"
"sync"
"golang.org/x/net/http2"
)
const (
// The default value of flow control window size in HTTP2 spec.
defaultWindowSize = 65535
// The initial window size for flow control.
initialWindowSize = defaultWindowSize // for an RPC
initialConnWindowSize = defaultWindowSize * 16 // for a connection
)
// 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.
type windowUpdate struct {
streamID uint32
increment uint32
}
func (*windowUpdate) item() {}
type settings struct {
ack bool
ss []http2.Setting
}
func (*settings) item() {}
type resetStream struct {
streamID uint32
code http2.ErrCode
}
func (*resetStream) item() {}
type goAway struct {
}
func (*goAway) item() {}
type flushIO struct {
}
func (*flushIO) item() {}
type ping struct {
ack bool
data [8]byte
}
func (*ping) item() {}
// quotaPool is a pool which accumulates the quota and sends it to acquire()
// when it is available.
type quotaPool struct {
c chan int
mu sync.Mutex
quota int
}
// newQuotaPool creates a quotaPool which has quota q available to consume.
func newQuotaPool(q int) *quotaPool {
qb := "aPool{
c: make(chan int, 1),
}
if q > 0 {
qb.c <- q
} else {
qb.quota = q
}
return qb
}
// add cancels the pending quota sent on acquired, incremented by v and sends
// it back on acquire.
func (qb *quotaPool) add(v int) {
qb.mu.Lock()
defer qb.mu.Unlock()
select {
case n := <-qb.c:
qb.quota += n
default:
}
qb.quota += v
if qb.quota <= 0 {
return
}
// After the pool has been created, this is the only place that sends on
// the channel. Since mu is held at this point and any quota that was sent
// on the channel has been retrieved, we know that this code will always
// place any positive quota value on the channel.
select {
case qb.c <- qb.quota:
qb.quota = 0
default:
}
}
// acquire returns the channel on which available quota amounts are sent.
func (qb *quotaPool) acquire() <-chan int {
return qb.c
}
// inFlow deals with inbound flow control
type inFlow struct {
// The inbound flow control limit for pending data.
limit uint32
mu sync.Mutex
// pendingData is the overall data which have been received but not been
// consumed by applications.
pendingData uint32
// The amount of data the application has consumed but grpc has not sent
// window update for them. Used to reduce window update frequency.
pendingUpdate uint32
}
// onData is invoked when some data frame is received. It updates pendingData.
func (f *inFlow) onData(n uint32) error {
f.mu.Lock()
defer f.mu.Unlock()
f.pendingData += n
if f.pendingData+f.pendingUpdate > f.limit {
return fmt.Errorf("received %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate, f.limit)
}
return nil
}
// onRead is invoked when the application reads the data. It returns the window size
// to be sent to the peer.
func (f *inFlow) onRead(n uint32) uint32 {
f.mu.Lock()
defer f.mu.Unlock()
if f.pendingData == 0 {
return 0
}
f.pendingData -= n
f.pendingUpdate += n
if f.pendingUpdate >= f.limit/4 {
wu := f.pendingUpdate
f.pendingUpdate = 0
return wu
}
return 0
}
func (f *inFlow) resetPendingData() uint32 {
f.mu.Lock()
defer f.mu.Unlock()
n := f.pendingData
f.pendingData = 0
return n
}
|
