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Streamline rate limiting

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Jakob Borg 2014-04-01 14:22:38 +02:00
parent 8e33288156
commit 76e0960a51
7 changed files with 908 additions and 16 deletions
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Godeps/Godeps.json generated
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@ -27,6 +27,10 @@
"ImportPath": "github.com/codegangsta/martini",
"Comment": "v0.1-142-g8659df7",
"Rev": "8659df7a51aebe6c6120268cd5a8b4c34fa8441a"
},
{
"ImportPath": "github.com/juju/ratelimit",
"Rev": "cbaa435c80a9716e086f25d409344b26c4039358"
}
]
}

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Godeps/_workspace/src/github.com/juju/ratelimit/LICENSE generated vendored Normal file
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This software is licensed under the LGPLv3, included below.
As a special exception to the GNU Lesser General Public License version 3
("LGPL3"), the copyright holders of this Library give you permission to
convey to a third party a Combined Work that links statically or dynamically
to this Library without providing any Minimal Corresponding Source or
Minimal Application Code as set out in 4d or providing the installation
information set out in section 4e, provided that you comply with the other
provisions of LGPL3 and provided that you meet, for the Application the
terms and conditions of the license(s) which apply to the Application.
Except as stated in this special exception, the provisions of LGPL3 will
continue to comply in full to this Library. If you modify this Library, you
may apply this exception to your version of this Library, but you are not
obliged to do so. If you do not wish to do so, delete this exception
statement from your version. This exception does not (and cannot) modify any
license terms which apply to the Application, with which you must still
comply.
GNU LESSER GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
This version of the GNU Lesser General Public License incorporates
the terms and conditions of version 3 of the GNU General Public
License, supplemented by the additional permissions listed below.
0. Additional Definitions.
As used herein, "this License" refers to version 3 of the GNU Lesser
General Public License, and the "GNU GPL" refers to version 3 of the GNU
General Public License.
"The Library" refers to a covered work governed by this License,
other than an Application or a Combined Work as defined below.
An "Application" is any work that makes use of an interface provided
by the Library, but which is not otherwise based on the Library.
Defining a subclass of a class defined by the Library is deemed a mode
of using an interface provided by the Library.
A "Combined Work" is a work produced by combining or linking an
Application with the Library. The particular version of the Library
with which the Combined Work was made is also called the "Linked
Version".
The "Minimal Corresponding Source" for a Combined Work means the
Corresponding Source for the Combined Work, excluding any source code
for portions of the Combined Work that, considered in isolation, are
based on the Application, and not on the Linked Version.
The "Corresponding Application Code" for a Combined Work means the
object code and/or source code for the Application, including any data
and utility programs needed for reproducing the Combined Work from the
Application, but excluding the System Libraries of the Combined Work.
1. Exception to Section 3 of the GNU GPL.
You may convey a covered work under sections 3 and 4 of this License
without being bound by section 3 of the GNU GPL.
2. Conveying Modified Versions.
If you modify a copy of the Library, and, in your modifications, a
facility refers to a function or data to be supplied by an Application
that uses the facility (other than as an argument passed when the
facility is invoked), then you may convey a copy of the modified
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a) under this License, provided that you make a good faith effort to
ensure that, in the event an Application does not supply the
function or data, the facility still operates, and performs
whatever part of its purpose remains meaningful, or
b) under the GNU GPL, with none of the additional permissions of
this License applicable to that copy.
3. Object Code Incorporating Material from Library Header Files.
The object code form of an Application may incorporate material from
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is a work based on the Library, and explaining where to find the
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The Free Software Foundation may publish revised and/or new versions
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versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the
Library as you received it specifies that a certain numbered version
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applies to it, you have the option of following the terms and
conditions either of that published version or of any later version
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received it does not specify a version number of the GNU Lesser
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Godeps/_workspace/src/github.com/juju/ratelimit/README.md generated vendored Normal file
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# ratelimit
--
import "github.com/juju/ratelimit"
The ratelimit package provides an efficient token bucket implementation. See
http://en.wikipedia.org/wiki/Token_bucket.
## Usage
#### func Reader
```go
func Reader(r io.Reader, bucket *Bucket) io.Reader
```
Reader returns a reader that is rate limited by the given token bucket. Each
token in the bucket represents one byte.
#### func Writer
```go
func Writer(w io.Writer, bucket *Bucket) io.Writer
```
Writer returns a reader that is rate limited by the given token bucket. Each
token in the bucket represents one byte.
#### type Bucket
```go
type Bucket struct {
}
```
Bucket represents a token bucket that fills at a predetermined rate. Methods on
Bucket may be called concurrently.
#### func NewBucket
```go
func NewBucket(fillInterval time.Duration, capacity int64) *Bucket
```
NewBucket returns a new token bucket that fills at the rate of one token every
fillInterval, up to the given maximum capacity. Both arguments must be positive.
The bucket is initially full.
#### func NewBucketWithRate
```go
func NewBucketWithRate(rate float64, capacity int64) *Bucket
```
NewBucketWithRate returns a token bucket that fills the bucket at the rate of
rate tokens per second up to the given maximum capacity. Because of limited
clock resolution, at high rates, the actual rate may be up to 1% different from
the specified rate.
#### func (*Bucket) Rate
```go
func (tb *Bucket) Rate() float64
```
Rate returns the fill rate of the bucket, in tokens per second.
#### func (*Bucket) Take
```go
func (tb *Bucket) Take(count int64) time.Duration
```
Take takes count tokens from the bucket without blocking. It returns the time
that the caller should wait until the tokens are actually available.
Note that if the request is irrevocable - there is no way to return tokens to
the bucket once this method commits us to taking them.
#### func (*Bucket) TakeAvailable
```go
func (tb *Bucket) TakeAvailable(count int64) int64
```
TakeAvailable takes up to count immediately available tokens from the bucket. It
returns the number of tokens removed, or zero if there are no available tokens.
It does not block.
#### func (*Bucket) TakeMaxDuration
```go
func (tb *Bucket) TakeMaxDuration(count int64, maxWait time.Duration) (time.Duration, bool)
```
TakeMaxDuration is like Take, except that it will only take tokens from the
bucket if the wait time for the tokens is no greater than maxWait.
If it would take longer than maxWait for the tokens to become available, it does
nothing and reports false, otherwise it returns the time that the caller should
wait until the tokens are actually available, and reports true.
#### func (*Bucket) Wait
```go
func (tb *Bucket) Wait(count int64)
```
Wait takes count tokens from the bucket, waiting until they are available.
#### func (*Bucket) WaitMaxDuration
```go
func (tb *Bucket) WaitMaxDuration(count int64, maxWait time.Duration) bool
```
WaitMaxDuration is like Wait except that it will only take tokens from the
bucket if it needs to wait for no greater than maxWait. It reports whether any
tokens have been removed from the bucket If no tokens have been removed, it
returns immediately.

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Godeps/_workspace/src/github.com/juju/ratelimit/ratelimit.go generated vendored Normal file
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// Copyright 2014 Canonical Ltd.
// Licensed under the LGPLv3 with static-linking exception.
// See LICENCE file for details.
// The ratelimit package provides an efficient token bucket implementation.
// See http://en.wikipedia.org/wiki/Token_bucket.
package ratelimit
import (
"strconv"
"sync"
"time"
)
// Bucket represents a token bucket that fills at a predetermined rate.
// Methods on Bucket may be called concurrently.
type Bucket struct {
startTime time.Time
capacity int64
quantum int64
fillInterval time.Duration
// The mutex guards the fields following it.
mu sync.Mutex
// avail holds the number of available tokens
// in the bucket, as of availTick ticks from startTime.
// It will be negative when there are consumers
// waiting for tokens.
avail int64
availTick int64
}
// NewBucket returns a new token bucket that fills at the
// rate of one token every fillInterval, up to the given
// maximum capacity. Both arguments must be
// positive. The bucket is initially full.
func NewBucket(fillInterval time.Duration, capacity int64) *Bucket {
return newBucketWithQuantum(fillInterval, capacity, 1)
}
// rateMargin specifes the allowed variance of actual
// rate from specified rate. 1% seems reasonable.
const rateMargin = 0.01
// NewBucketWithRate returns a token bucket that fills the bucket
// at the rate of rate tokens per second up to the given
// maximum capacity. Because of limited clock resolution,
// at high rates, the actual rate may be up to 1% different from the
// specified rate.
func NewBucketWithRate(rate float64, capacity int64) *Bucket {
for quantum := int64(1); quantum < 1<<50; quantum = nextQuantum(quantum) {
fillInterval := time.Duration(1e9 * float64(quantum) / rate)
if fillInterval <= 0 {
continue
}
tb := newBucketWithQuantum(fillInterval, capacity, quantum)
if diff := abs(tb.Rate() - rate); diff/rate <= rateMargin {
return tb
}
}
panic("cannot find suitable quantum for " + strconv.FormatFloat(rate, 'g', -1, 64))
}
// nextQuantum returns the next quantum to try after q.
// We grow the quantum exponentially, but slowly, so we
// get a good fit in the lower numbers.
func nextQuantum(q int64) int64 {
q1 := q * 11 / 10
if q1 == q {
q1++
}
return q1
}
// newBucketWithQuantum is similar to NewBucket, but allows
// the specification of the quantum size - quantum tokens
// are added every fillInterval. This is so that we can get accurate
// rates even when we want to add more than one token per ns.
func newBucketWithQuantum(fillInterval time.Duration, capacity, quantum int64) *Bucket {
if fillInterval <= 0 {
panic("token bucket fill interval is not > 0")
}
if capacity <= 0 {
panic("token bucket capacity is not > 0")
}
if quantum <= 0 {
panic("token bucket quantum is not > 0")
}
return &Bucket{
startTime: time.Now(),
capacity: capacity,
quantum: quantum,
avail: capacity,
fillInterval: fillInterval,
}
}
// Wait takes count tokens from the bucket, waiting until they are
// available.
func (tb *Bucket) Wait(count int64) {
if d := tb.Take(count); d > 0 {
time.Sleep(d)
}
}
// WaitMaxDuration is like Wait except that it will
// only take tokens from the bucket if it needs to wait
// for no greater than maxWait. It reports whether
// any tokens have been removed from the bucket
// If no tokens have been removed, it returns immediately.
func (tb *Bucket) WaitMaxDuration(count int64, maxWait time.Duration) bool {
d, ok := tb.TakeMaxDuration(count, maxWait)
if d > 0 {
time.Sleep(d)
}
return ok
}
const infinityDuration time.Duration = 0x7fffffffffffffff
// Take takes count tokens from the bucket without blocking. It returns
// the time that the caller should wait until the tokens are actually
// available.
//
// Note that if the request is irrevocable - there is no way to return
// tokens to the bucket once this method commits us to taking them.
func (tb *Bucket) Take(count int64) time.Duration {
d, _ := tb.take(time.Now(), count, infinityDuration)
return d
}
// TakeMaxDuration is like Take, except that
// it will only take tokens from the bucket if the wait
// time for the tokens is no greater than maxWait.
//
// If it would take longer than maxWait for the tokens
// to become available, it does nothing and reports false,
// otherwise it returns the time that the caller should
// wait until the tokens are actually available, and reports
// true.
func (tb *Bucket) TakeMaxDuration(count int64, maxWait time.Duration) (time.Duration, bool) {
return tb.take(time.Now(), count, maxWait)
}
// TakeAvailable takes up to count immediately available tokens from the
// bucket. It returns the number of tokens removed, or zero if there are
// no available tokens. It does not block.
func (tb *Bucket) TakeAvailable(count int64) int64 {
return tb.takeAvailable(time.Now(), count)
}
// takeAvailable is the internal version of TakeAvailable - it takes the
// current time as an argument to enable easy testing.
func (tb *Bucket) takeAvailable(now time.Time, count int64) int64 {
if count <= 0 {
return 0
}
tb.mu.Lock()
defer tb.mu.Unlock()
tb.adjust(now)
if tb.avail <= 0 {
return 0
}
if count > tb.avail {
count = tb.avail
}
tb.avail -= count
return count
}
// Rate returns the fill rate of the bucket, in tokens per second.
func (tb *Bucket) Rate() float64 {
return 1e9 * float64(tb.quantum) / float64(tb.fillInterval)
}
// take is the internal version of Take - it takes the current time as
// an argument to enable easy testing.
func (tb *Bucket) take(now time.Time, count int64, maxWait time.Duration) (time.Duration, bool) {
if count <= 0 {
return 0, true
}
tb.mu.Lock()
defer tb.mu.Unlock()
currentTick := tb.adjust(now)
avail := tb.avail - count
if avail >= 0 {
tb.avail = avail
return 0, true
}
// Round up the missing tokens to the nearest multiple
// of quantum - the tokens won't be available until
// that tick.
endTick := currentTick + (-avail+tb.quantum-1)/tb.quantum
endTime := tb.startTime.Add(time.Duration(endTick) * tb.fillInterval)
waitTime := endTime.Sub(now)
if waitTime > maxWait {
return 0, false
}
tb.avail = avail
return waitTime, true
}
// adjust adjusts the current bucket capacity based on the current time.
// It returns the current tick.
func (tb *Bucket) adjust(now time.Time) (currentTick int64) {
currentTick = int64(now.Sub(tb.startTime) / tb.fillInterval)
if tb.avail >= tb.capacity {
return
}
tb.avail += (currentTick - tb.availTick) * tb.quantum
if tb.avail > tb.capacity {
tb.avail = tb.capacity
}
tb.availTick = currentTick
return
}
func abs(f float64) float64 {
if f < 0 {
return -f
}
return f
}

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// Copyright 2014 Canonical Ltd.
// Licensed under the LGPLv3 with static-linking exception.
// See LICENCE file for details.
package ratelimit
import (
gc "launchpad.net/gocheck"
"testing"
"time"
)
func TestPackage(t *testing.T) {
gc.TestingT(t)
}
type rateLimitSuite struct{}
var _ = gc.Suite(rateLimitSuite{})
type takeReq struct {
time time.Duration
count int64
expectWait time.Duration
}
var takeTests = []struct {
about string
fillInterval time.Duration
capacity int64
reqs []takeReq
}{{
about: "serial requests",
fillInterval: 250 * time.Millisecond,
capacity: 10,
reqs: []takeReq{{
time: 0,
count: 0,
expectWait: 0,
}, {
time: 0,
count: 10,
expectWait: 0,
}, {
time: 0,
count: 1,
expectWait: 250 * time.Millisecond,
}, {
time: 250 * time.Millisecond,
count: 1,
expectWait: 250 * time.Millisecond,
}},
}, {
about: "concurrent requests",
fillInterval: 250 * time.Millisecond,
capacity: 10,
reqs: []takeReq{{
time: 0,
count: 10,
expectWait: 0,
}, {
time: 0,
count: 2,
expectWait: 500 * time.Millisecond,
}, {
time: 0,
count: 2,
expectWait: 1000 * time.Millisecond,
}, {
time: 0,
count: 1,
expectWait: 1250 * time.Millisecond,
}},
}, {
about: "more than capacity",
fillInterval: 1 * time.Millisecond,
capacity: 10,
reqs: []takeReq{{
time: 0,
count: 10,
expectWait: 0,
}, {
time: 20 * time.Millisecond,
count: 15,
expectWait: 5 * time.Millisecond,
}},
}, {
about: "sub-quantum time",
fillInterval: 10 * time.Millisecond,
capacity: 10,
reqs: []takeReq{{
time: 0,
count: 10,
expectWait: 0,
}, {
time: 7 * time.Millisecond,
count: 1,
expectWait: 3 * time.Millisecond,
}, {
time: 8 * time.Millisecond,
count: 1,
expectWait: 12 * time.Millisecond,
}},
}, {
about: "within capacity",
fillInterval: 10 * time.Millisecond,
capacity: 5,
reqs: []takeReq{{
time: 0,
count: 5,
expectWait: 0,
}, {
time: 60 * time.Millisecond,
count: 5,
expectWait: 0,
}, {
time: 60 * time.Millisecond,
count: 1,
expectWait: 10 * time.Millisecond,
}, {
time: 80 * time.Millisecond,
count: 2,
expectWait: 10 * time.Millisecond,
}},
}}
func (rateLimitSuite) TestTake(c *gc.C) {
for i, test := range takeTests {
tb := NewBucket(test.fillInterval, test.capacity)
for j, req := range test.reqs {
d, ok := tb.take(tb.startTime.Add(req.time), req.count, infinityDuration)
c.Assert(ok, gc.Equals, true)
if d != req.expectWait {
c.Fatalf("test %d.%d, %s, got %v want %v", i, j, test.about, d, req.expectWait)
}
}
}
}
func (rateLimitSuite) TestTakeMaxDuration(c *gc.C) {
for i, test := range takeTests {
tb := NewBucket(test.fillInterval, test.capacity)
for j, req := range test.reqs {
if req.expectWait > 0 {
d, ok := tb.take(tb.startTime.Add(req.time), req.count, req.expectWait-1)
c.Assert(ok, gc.Equals, false)
c.Assert(d, gc.Equals, time.Duration(0))
}
d, ok := tb.take(tb.startTime.Add(req.time), req.count, req.expectWait)
c.Assert(ok, gc.Equals, true)
if d != req.expectWait {
c.Fatalf("test %d.%d, %s, got %v want %v", i, j, test.about, d, req.expectWait)
}
}
}
}
type takeAvailableReq struct {
time time.Duration
count int64
expect int64
}
var takeAvailableTests = []struct {
about string
fillInterval time.Duration
capacity int64
reqs []takeAvailableReq
}{{
about: "serial requests",
fillInterval: 250 * time.Millisecond,
capacity: 10,
reqs: []takeAvailableReq{{
time: 0,
count: 0,
expect: 0,
}, {
time: 0,
count: 10,
expect: 10,
}, {
time: 0,
count: 1,
expect: 0,
}, {
time: 250 * time.Millisecond,
count: 1,
expect: 1,
}},
}, {
about: "concurrent requests",
fillInterval: 250 * time.Millisecond,
capacity: 10,
reqs: []takeAvailableReq{{
time: 0,
count: 5,
expect: 5,
}, {
time: 0,
count: 2,
expect: 2,
}, {
time: 0,
count: 5,
expect: 3,
}, {
time: 0,
count: 1,
expect: 0,
}},
}, {
about: "more than capacity",
fillInterval: 1 * time.Millisecond,
capacity: 10,
reqs: []takeAvailableReq{{
time: 0,
count: 10,
expect: 10,
}, {
time: 20 * time.Millisecond,
count: 15,
expect: 10,
}},
}, {
about: "within capacity",
fillInterval: 10 * time.Millisecond,
capacity: 5,
reqs: []takeAvailableReq{{
time: 0,
count: 5,
expect: 5,
}, {
time: 60 * time.Millisecond,
count: 5,
expect: 5,
}, {
time: 70 * time.Millisecond,
count: 1,
expect: 1,
}},
}}
func (rateLimitSuite) TestTakeAvailable(c *gc.C) {
for i, test := range takeAvailableTests {
tb := NewBucket(test.fillInterval, test.capacity)
for j, req := range test.reqs {
d := tb.takeAvailable(tb.startTime.Add(req.time), req.count)
if d != req.expect {
c.Fatalf("test %d.%d, %s, got %v want %v", i, j, test.about, d, req.expect)
}
}
}
}
func (rateLimitSuite) TestPanics(c *gc.C) {
c.Assert(func() { NewBucket(0, 1) }, gc.PanicMatches, "token bucket fill interval is not > 0")
c.Assert(func() { NewBucket(-2, 1) }, gc.PanicMatches, "token bucket fill interval is not > 0")
c.Assert(func() { NewBucket(1, 0) }, gc.PanicMatches, "token bucket capacity is not > 0")
c.Assert(func() { NewBucket(1, -2) }, gc.PanicMatches, "token bucket capacity is not > 0")
}
func isCloseTo(x, y, tolerance float64) bool {
return abs(x-y)/y < tolerance
}
func (rateLimitSuite) TestRate(c *gc.C) {
tb := NewBucket(1, 1)
if !isCloseTo(tb.Rate(), 1e9, 0.00001) {
c.Fatalf("got %v want 1e9", tb.Rate())
}
tb = NewBucket(2*time.Second, 1)
if !isCloseTo(tb.Rate(), 0.5, 0.00001) {
c.Fatalf("got %v want 0.5", tb.Rate())
}
tb = newBucketWithQuantum(100*time.Millisecond, 1, 5)
if !isCloseTo(tb.Rate(), 50, 0.00001) {
c.Fatalf("got %v want 50", tb.Rate())
}
}
func checkRate(c *gc.C, rate float64) {
tb := NewBucketWithRate(rate, 1<<62)
if !isCloseTo(tb.Rate(), rate, rateMargin) {
c.Fatalf("got %g want %v", tb.Rate(), rate)
}
d, ok := tb.take(tb.startTime, 1<<62, infinityDuration)
c.Assert(ok, gc.Equals, true)
c.Assert(d, gc.Equals, time.Duration(0))
// Check that the actual rate is as expected by
// asking for a not-quite multiple of the bucket's
// quantum and checking that the wait time
// correct.
d, ok = tb.take(tb.startTime, tb.quantum*2-tb.quantum/2, infinityDuration)
c.Assert(ok, gc.Equals, true)
expectTime := 1e9 * float64(tb.quantum) * 2 / rate
if !isCloseTo(float64(d), expectTime, rateMargin) {
c.Fatalf("rate %g: got %g want %v", rate, float64(d), expectTime)
}
}
func (rateLimitSuite) TestNewWithRate(c *gc.C) {
for rate := float64(1); rate < 1e6; rate += 7 {
checkRate(c, rate)
}
for _, rate := range []float64{
1024 * 1024 * 1024,
1e-5,
0.9e-5,
0.5,
0.9,
0.9e8,
3e12,
4e18,
} {
checkRate(c, rate)
checkRate(c, rate/3)
checkRate(c, rate*1.3)
}
}
func BenchmarkWait(b *testing.B) {
tb := NewBucket(1, 16*1024)
for i := b.N - 1; i >= 0; i-- {
tb.Wait(1)
}
}

51
Godeps/_workspace/src/github.com/juju/ratelimit/reader.go generated vendored Normal file
View File

@ -0,0 +1,51 @@
// Copyright 2014 Canonical Ltd.
// Licensed under the LGPLv3 with static-linking exception.
// See LICENCE file for details.
package ratelimit
import "io"
type reader struct {
r io.Reader
bucket *Bucket
}
// Reader returns a reader that is rate limited by
// the given token bucket. Each token in the bucket
// represents one byte.
func Reader(r io.Reader, bucket *Bucket) io.Reader {
return &reader{
r: r,
bucket: bucket,
}
}
func (r *reader) Read(buf []byte) (int, error) {
n, err := r.r.Read(buf)
if n <= 0 {
return n, err
}
r.bucket.Wait(int64(n))
return n, err
}
type writer struct {
w io.Writer
bucket *Bucket
}
// Writer returns a reader that is rate limited by
// the given token bucket. Each token in the bucket
// represents one byte.
func Writer(w io.Writer, bucket *Bucket) io.Writer {
return &writer{
w: w,
bucket: bucket,
}
}
func (w *writer) Write(buf []byte) (int, error) {
w.bucket.Wait(int64(len(buf)))
return w.w.Write(buf)
}

20
cmd/syncthing/model.go
View File

@ -18,6 +18,7 @@ import (
"github.com/calmh/syncthing/lamport"
"github.com/calmh/syncthing/protocol"
"github.com/calmh/syncthing/scanner"
"github.com/juju/ratelimit"
)
type Model struct {
@ -35,7 +36,7 @@ type Model struct {
sup suppressor
limitRequestRate chan struct{}
limitRequestRate *ratelimit.Bucket
addedRepo bool
started bool
@ -66,18 +67,7 @@ func NewModel(maxChangeBw int) *Model {
}
func (m *Model) LimitRate(kbps int) {
m.limitRequestRate = make(chan struct{}, kbps)
n := kbps/10 + 1
go func() {
for {
time.Sleep(100 * time.Millisecond)
for i := 0; i < n; i++ {
select {
case m.limitRequestRate <- struct{}{}:
}
}
}
}()
m.limitRequestRate = ratelimit.NewBucketWithRate(float64(kbps), int64(5*kbps))
}
// StartRW starts read/write processing on the current model. When in
@ -362,9 +352,7 @@ func (m *Model) Request(nodeID, repo, name string, offset int64, size int) ([]by
}
if m.limitRequestRate != nil {
for s := 0; s < len(buf); s += 1024 {
<-m.limitRequestRate
}
m.limitRequestRate.Wait(int64(size / 1024))
}
return buf, nil