/
respondent.go
291 lines (252 loc) · 5.34 KB
/
respondent.go
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
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
// Copyright 2018 The Mangos Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use 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 respondent implements the RESPONDENT protocol. This protocol
// receives SURVEYOR requests, and responds with an answer.
package respondent
import (
"encoding/binary"
"sync"
"time"
"nanomsg.org/go-mangos"
)
type resp struct {
sock mangos.ProtocolSocket
peers map[uint32]*respPeer
raw bool
ttl int
backbuf []byte
backtrace []byte
w mangos.Waiter
sync.Mutex
}
type respPeer struct {
q chan *mangos.Message
ep mangos.Endpoint
x *resp
}
func (x *resp) Init(sock mangos.ProtocolSocket) {
x.sock = sock
x.ttl = 8
x.peers = make(map[uint32]*respPeer)
x.w.Init()
x.backbuf = make([]byte, 0, 64)
x.sock.SetSendError(mangos.ErrProtoState)
x.w.Add()
go x.sender()
}
func (x *resp) Shutdown(expire time.Time) {
peers := make(map[uint32]*respPeer)
x.w.WaitAbsTimeout(expire)
x.Lock()
for id, peer := range x.peers {
delete(x.peers, id)
peers[id] = peer
}
x.Unlock()
for id, peer := range peers {
delete(peers, id)
mangos.DrainChannel(peer.q, expire)
close(peer.q)
}
}
func (x *resp) sender() {
// This is pretty easy because we have only one peer at a time.
// If the peer goes away, we'll just drop the message on the floor.
defer x.w.Done()
cq := x.sock.CloseChannel()
sq := x.sock.SendChannel()
for {
var m *mangos.Message
select {
case m = <-sq:
if m == nil {
sq = x.sock.SendChannel()
continue
}
case <-cq:
return
}
// Lop off the 32-bit peer/pipe ID. If absent, drop.
if len(m.Header) < 4 {
m.Free()
continue
}
id := binary.BigEndian.Uint32(m.Header)
m.Header = m.Header[4:]
x.Lock()
peer := x.peers[id]
x.Unlock()
if peer == nil {
m.Free()
continue
}
// Put it on the outbound queue
select {
case peer.q <- m:
default:
// Backpressure, drop it.
m.Free()
}
}
}
// When sending, we should have the survey ID in the header.
func (peer *respPeer) sender() {
for {
m := <-peer.q
if m == nil {
break
}
if peer.ep.SendMsg(m) != nil {
m.Free()
break
}
}
}
func (x *resp) receiver(ep mangos.Endpoint) {
rq := x.sock.RecvChannel()
cq := x.sock.CloseChannel()
outer:
for {
m := ep.RecvMsg()
if m == nil {
return
}
v := ep.GetID()
m.Header = append(m.Header,
byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
hops := 0
for {
if hops >= x.ttl {
m.Free() // ErrTooManyHops
continue outer
}
hops++
if len(m.Body) < 4 {
m.Free()
continue outer
}
m.Header = append(m.Header, m.Body[:4]...)
m.Body = m.Body[4:]
if m.Header[len(m.Header)-4]&0x80 != 0 {
break
}
}
select {
case rq <- m:
case <-cq:
m.Free()
return
}
}
}
func (x *resp) RecvHook(m *mangos.Message) bool {
if x.raw {
// Raw mode receivers get the message unadulterated.
return true
}
if len(m.Header) < 4 {
return false
}
x.Lock()
x.backbuf = x.backbuf[0:0] // avoid allocations
x.backtrace = append(x.backbuf, m.Header...)
x.Unlock()
x.sock.SetSendError(nil)
return true
}
func (x *resp) SendHook(m *mangos.Message) bool {
if x.raw {
// Raw mode senders expected to have prepared header already.
return true
}
x.sock.SetSendError(mangos.ErrProtoState)
x.Lock()
m.Header = append(m.Header[0:0], x.backtrace...)
x.backtrace = nil
x.Unlock()
if len(m.Header) == 0 {
return false
}
return true
}
func (x *resp) AddEndpoint(ep mangos.Endpoint) {
peer := &respPeer{ep: ep, x: x, q: make(chan *mangos.Message, 1)}
x.Lock()
x.peers[ep.GetID()] = peer
x.Unlock()
go x.receiver(ep)
go peer.sender()
}
func (x *resp) RemoveEndpoint(ep mangos.Endpoint) {
id := ep.GetID()
x.Lock()
peer := x.peers[id]
delete(x.peers, id)
x.Unlock()
if peer != nil {
close(peer.q)
}
}
func (*resp) Number() uint16 {
return mangos.ProtoRespondent
}
func (*resp) PeerNumber() uint16 {
return mangos.ProtoSurveyor
}
func (*resp) Name() string {
return "respondent"
}
func (*resp) PeerName() string {
return "surveyor"
}
func (x *resp) SetOption(name string, v interface{}) error {
var ok bool
switch name {
case mangos.OptionRaw:
if x.raw, ok = v.(bool); !ok {
return mangos.ErrBadValue
}
if x.raw {
x.sock.SetSendError(nil)
} else {
x.sock.SetSendError(mangos.ErrProtoState)
}
return nil
case mangos.OptionTTL:
if ttl, ok := v.(int); !ok {
return mangos.ErrBadValue
} else if ttl < 1 || ttl > 255 {
return mangos.ErrBadValue
} else {
x.ttl = ttl
}
return nil
default:
return mangos.ErrBadOption
}
}
func (x *resp) GetOption(name string) (interface{}, error) {
switch name {
case mangos.OptionRaw:
return x.raw, nil
case mangos.OptionTTL:
return x.ttl, nil
default:
return nil, mangos.ErrBadOption
}
}
// NewSocket allocates a new Socket using the RESPONDENT protocol.
func NewSocket() (mangos.Socket, error) {
return mangos.MakeSocket(&resp{}), nil
}