forked from syncthing/syncthing
/
limiter.go
347 lines (296 loc) · 9.88 KB
/
limiter.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
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
// Copyright (C) 2017 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package connections
import (
"context"
"fmt"
"io"
"sync/atomic"
"github.com/jector20/syncthing/lib/config"
"github.com/jector20/syncthing/lib/protocol"
"github.com/jector20/syncthing/lib/sync"
"golang.org/x/time/rate"
)
// limiter manages a read and write rate limit, reacting to config changes
// as appropriate.
type limiter struct {
myID protocol.DeviceID
mu sync.Mutex
write *rate.Limiter
read *rate.Limiter
limitsLAN atomic.Bool
deviceReadLimiters map[protocol.DeviceID]*rate.Limiter
deviceWriteLimiters map[protocol.DeviceID]*rate.Limiter
}
type waiter interface {
// This is the rate limiting operation
WaitN(ctx context.Context, n int) error
Limit() rate.Limit
}
const (
limiterBurstSize = 4 * 128 << 10
)
func newLimiter(myId protocol.DeviceID, cfg config.Wrapper) *limiter {
l := &limiter{
myID: myId,
write: rate.NewLimiter(rate.Inf, limiterBurstSize),
read: rate.NewLimiter(rate.Inf, limiterBurstSize),
mu: sync.NewMutex(),
deviceReadLimiters: make(map[protocol.DeviceID]*rate.Limiter),
deviceWriteLimiters: make(map[protocol.DeviceID]*rate.Limiter),
}
cfg.Subscribe(l)
prev := config.Configuration{Options: config.OptionsConfiguration{MaxRecvKbps: -1, MaxSendKbps: -1}}
l.CommitConfiguration(prev, cfg.RawCopy())
return l
}
// This function sets limiters according to corresponding DeviceConfiguration
func (lim *limiter) setLimitsLocked(device config.DeviceConfiguration) bool {
readLimiter := lim.getReadLimiterLocked(device.DeviceID)
writeLimiter := lim.getWriteLimiterLocked(device.DeviceID)
// limiters for this device are created so we can store previous rates for logging
previousReadLimit := readLimiter.Limit()
previousWriteLimit := writeLimiter.Limit()
currentReadLimit := rate.Limit(device.MaxRecvKbps) * 1024
currentWriteLimit := rate.Limit(device.MaxSendKbps) * 1024
if device.MaxSendKbps <= 0 {
currentWriteLimit = rate.Inf
}
if device.MaxRecvKbps <= 0 {
currentReadLimit = rate.Inf
}
// Nothing about this device has changed. Start processing next device
if previousWriteLimit == currentWriteLimit && previousReadLimit == currentReadLimit {
return false
}
readLimiter.SetLimit(currentReadLimit)
writeLimiter.SetLimit(currentWriteLimit)
return true
}
// This function handles removing, adding and updating of device limiters.
func (lim *limiter) processDevicesConfigurationLocked(from, to config.Configuration) {
seen := make(map[protocol.DeviceID]struct{})
// Mark devices which should not be removed, create new limiters if needed and assign new limiter rate
for _, dev := range to.Devices {
if dev.DeviceID == lim.myID {
// This limiter was created for local device. Should skip this device
continue
}
seen[dev.DeviceID] = struct{}{}
if lim.setLimitsLocked(dev) {
readLimitStr := "is unlimited"
if dev.MaxRecvKbps > 0 {
readLimitStr = fmt.Sprintf("limit is %d KiB/s", dev.MaxRecvKbps)
}
writeLimitStr := "is unlimited"
if dev.MaxSendKbps > 0 {
writeLimitStr = fmt.Sprintf("limit is %d KiB/s", dev.MaxSendKbps)
}
l.Infof("Device %s send rate %s, receive rate %s", dev.DeviceID, writeLimitStr, readLimitStr)
}
}
// Delete remote devices which were removed in new configuration
for _, dev := range from.Devices {
if _, ok := seen[dev.DeviceID]; !ok {
l.Debugf("deviceID: %s should be removed", dev.DeviceID)
delete(lim.deviceWriteLimiters, dev.DeviceID)
delete(lim.deviceReadLimiters, dev.DeviceID)
}
}
}
func (lim *limiter) CommitConfiguration(from, to config.Configuration) bool {
// to ensure atomic update of configuration
lim.mu.Lock()
defer lim.mu.Unlock()
// Delete, add or update limiters for devices
lim.processDevicesConfigurationLocked(from, to)
if from.Options.MaxRecvKbps == to.Options.MaxRecvKbps &&
from.Options.MaxSendKbps == to.Options.MaxSendKbps &&
from.Options.LimitBandwidthInLan == to.Options.LimitBandwidthInLan {
return true
}
limited := false
sendLimitStr := "is unlimited"
recvLimitStr := "is unlimited"
// The rate variables are in KiB/s in the config (despite the camel casing
// of the name). We multiply by 1024 to get bytes/s.
if to.Options.MaxRecvKbps <= 0 {
lim.read.SetLimit(rate.Inf)
} else {
lim.read.SetLimit(1024 * rate.Limit(to.Options.MaxRecvKbps))
recvLimitStr = fmt.Sprintf("limit is %d KiB/s", to.Options.MaxRecvKbps)
limited = true
}
if to.Options.MaxSendKbps <= 0 {
lim.write.SetLimit(rate.Inf)
} else {
lim.write.SetLimit(1024 * rate.Limit(to.Options.MaxSendKbps))
sendLimitStr = fmt.Sprintf("limit is %d KiB/s", to.Options.MaxSendKbps)
limited = true
}
lim.limitsLAN.Store(to.Options.LimitBandwidthInLan)
l.Infof("Overall send rate %s, receive rate %s", sendLimitStr, recvLimitStr)
if limited {
if to.Options.LimitBandwidthInLan {
l.Infoln("Rate limits apply to LAN connections")
} else {
l.Infoln("Rate limits do not apply to LAN connections")
}
}
return true
}
func (*limiter) String() string {
// required by config.Committer interface
return "connections.limiter"
}
func (lim *limiter) getLimiters(remoteID protocol.DeviceID, rw io.ReadWriter, isLAN bool) (io.Reader, io.Writer) {
lim.mu.Lock()
wr := lim.newLimitedWriterLocked(remoteID, rw, isLAN)
rd := lim.newLimitedReaderLocked(remoteID, rw, isLAN)
lim.mu.Unlock()
return rd, wr
}
func (lim *limiter) newLimitedReaderLocked(remoteID protocol.DeviceID, r io.Reader, isLAN bool) io.Reader {
return &limitedReader{
reader: r,
waiterHolder: waiterHolder{
waiter: totalWaiter{lim.getReadLimiterLocked(remoteID), lim.read},
limitsLAN: &lim.limitsLAN,
isLAN: isLAN,
},
}
}
func (lim *limiter) newLimitedWriterLocked(remoteID protocol.DeviceID, w io.Writer, isLAN bool) io.Writer {
return &limitedWriter{
writer: w,
waiterHolder: waiterHolder{
waiter: totalWaiter{lim.getWriteLimiterLocked(remoteID), lim.write},
limitsLAN: &lim.limitsLAN,
isLAN: isLAN,
},
}
}
func (lim *limiter) getReadLimiterLocked(deviceID protocol.DeviceID) *rate.Limiter {
return getRateLimiter(lim.deviceReadLimiters, deviceID)
}
func (lim *limiter) getWriteLimiterLocked(deviceID protocol.DeviceID) *rate.Limiter {
return getRateLimiter(lim.deviceWriteLimiters, deviceID)
}
func getRateLimiter(m map[protocol.DeviceID]*rate.Limiter, deviceID protocol.DeviceID) *rate.Limiter {
limiter, ok := m[deviceID]
if !ok {
limiter = rate.NewLimiter(rate.Inf, limiterBurstSize)
m[deviceID] = limiter
}
return limiter
}
// limitedReader is a rate limited io.Reader
type limitedReader struct {
reader io.Reader
waiterHolder
}
func (r *limitedReader) Read(buf []byte) (int, error) {
n, err := r.reader.Read(buf)
if !r.unlimited() {
r.take(n)
}
return n, err
}
// limitedWriter is a rate limited io.Writer
type limitedWriter struct {
writer io.Writer
waiterHolder
}
func (w *limitedWriter) Write(buf []byte) (int, error) {
if w.unlimited() {
return w.writer.Write(buf)
}
// This does (potentially) multiple smaller writes in order to be less
// bursty with large writes and slow rates. At the same time we don't
// want to do hilarious amounts of tiny writes when the rate is high, so
// try to be a bit adaptable. We range from the minimum write size of 1
// KiB up to the limiter burst size, aiming for about a write every
// 10ms.
singleWriteSize := int(w.waiter.Limit() / 100) // 10ms worth of data
singleWriteSize = ((singleWriteSize / 1024) + 1) * 1024 // round up to the next kibibyte
if singleWriteSize > limiterBurstSize {
singleWriteSize = limiterBurstSize
}
written := 0
for written < len(buf) {
toWrite := singleWriteSize
if toWrite > len(buf)-written {
toWrite = len(buf) - written
}
w.take(toWrite)
n, err := w.writer.Write(buf[written : written+toWrite])
written += n
if err != nil {
return written, err
}
}
return written, nil
}
// waiterHolder is the common functionality around having and evaluating a
// waiter, valid for both writers and readers
type waiterHolder struct {
waiter waiter
limitsLAN *atomic.Bool
isLAN bool
}
// unlimited returns true if the waiter is not limiting the rate
func (w waiterHolder) unlimited() bool {
if w.isLAN && !w.limitsLAN.Load() {
return true
}
return w.waiter.Limit() == rate.Inf
}
// take is a utility function to consume tokens, because no call to WaitN
// must be larger than the limiter burst size or it will hang.
func (w waiterHolder) take(tokens int) {
// For writes we already split the buffer into smaller operations so those
// will always end up in the fast path below. For reads, however, we don't
// control the size of the incoming buffer and don't split the calls
// into the lower level reads so we might get a large amount of data and
// end up in the loop further down.
if tokens <= limiterBurstSize {
// Fast path. We won't get an error from WaitN as we don't pass a
// context with a deadline.
_ = w.waiter.WaitN(context.TODO(), tokens)
return
}
for tokens > 0 {
// Consume limiterBurstSize tokens at a time until we're done.
if tokens > limiterBurstSize {
_ = w.waiter.WaitN(context.TODO(), limiterBurstSize)
tokens -= limiterBurstSize
} else {
_ = w.waiter.WaitN(context.TODO(), tokens)
tokens = 0
}
}
}
// totalWaiter waits for all of the waiters
type totalWaiter []waiter
func (tw totalWaiter) WaitN(ctx context.Context, n int) error {
for _, w := range tw {
if err := w.WaitN(ctx, n); err != nil {
// error here is context cancellation, most likely, so we abort
// early
return err
}
}
return nil
}
func (tw totalWaiter) Limit() rate.Limit {
min := rate.Inf
for _, w := range tw {
if l := w.Limit(); l < min {
min = l
}
}
return min
}