Rate limit using leaky bucket algorithm

CHANGES.md

@@ -1,3 +1,7 @@
+# May, 2014
+
+* Improved rate limiting using leaky bucket (PR #29)
+
 # Apr, 2014
 
 * LimitRate now discards read buffer (PR #28)

Makefile

@@ -1,7 +1,7 @@
 default:	test
 
 test:	*.go
-	go test -v
+	go test -v ./...
 
 fmt:
 	gofmt -w .

ratelimiter/Licence

@@ -0,0 +1,7 @@
+Copyright (C) 2013 99designs
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

ratelimiter/leakybucket.go

@@ -0,0 +1,97 @@
+// Package ratelimiter implements the Leaky Bucket ratelimiting algorithm with memcached and in-memory backends.
+package ratelimiter
+
+import (
+	"time"
+)
+
+type LeakyBucket struct {
+	Size         uint16
+	Fill         float64
+	LeakInterval time.Duration // time.Duration for 1 unit of size to leak
+	Lastupdate   time.Time
+	Now          func() time.Time
+}
+
+func NewLeakyBucket(size uint16, leakInterval time.Duration) *LeakyBucket {
+	bucket := LeakyBucket{
+		Size:         size,
+		Fill:         0,
+		LeakInterval: leakInterval,
+		Now:          time.Now,
+		Lastupdate:   time.Now(),
+	}
+
+	return &bucket
+}
+
+func (b *LeakyBucket) updateFill() {
+	now := b.Now()
+	if b.Fill > 0 {
+		elapsed := now.Sub(b.Lastupdate)
+
+		b.Fill -= float64(elapsed) / float64(b.LeakInterval)
+		if b.Fill < 0 {
+			b.Fill = 0
+		}
+	}
+	b.Lastupdate = now
+}
+
+func (b *LeakyBucket) Pour(amount uint16) bool {
+	b.updateFill()
+
+	var newfill float64 = b.Fill + float64(amount)
+
+	if newfill > float64(b.Size) {
+		return false
+	}
+
+	b.Fill = newfill
+
+	return true
+}
+
+// The time at which this bucket will be completely drained
+func (b *LeakyBucket) DrainedAt() time.Time {
+	return b.Lastupdate.Add(time.Duration(b.Fill * float64(b.LeakInterval)))
+}
+
+// The duration until this bucket is completely drained
+func (b *LeakyBucket) TimeToDrain() time.Duration {
+	return b.DrainedAt().Sub(b.Now())
+}
+
+func (b *LeakyBucket) TimeSinceLastUpdate() time.Duration {
+	return b.Now().Sub(b.Lastupdate)
+}
+
+type LeakyBucketSer struct {
+	Size         uint16
+	Fill         float64
+	LeakInterval time.Duration // time.Duration for 1 unit of size to leak
+	Lastupdate   time.Time
+}
+
+func (b *LeakyBucket) Serialise() *LeakyBucketSer {
+	bucket := LeakyBucketSer{
+		Size:         b.Size,
+		Fill:         b.Fill,
+		LeakInterval: b.LeakInterval,
+		Lastupdate:   b.Lastupdate,
+	}
+
+	return &bucket
+}
+
+func (b *LeakyBucketSer) DeSerialise() *LeakyBucket {
+	bucket := LeakyBucket{
+		Size:         b.Size,
+		Fill:         b.Fill,
+		LeakInterval: b.LeakInterval,
+		Lastupdate:   b.Lastupdate,
+		Now:          time.Now,
+	}
+
+	return &bucket
+}

ratelimiter/leakybucket_test.go

@@ -0,0 +1,73 @@
+package ratelimiter
+
+import (
+	"testing"
+	"time"
+)
+
+func TestPour(t *testing.T) {
+	bucket := NewLeakyBucket(60, time.Second)
+	bucket.Lastupdate = time.Unix(0, 0)
+
+	bucket.Now = func() time.Time { return time.Unix(1, 0) }
+
+	if bucket.Pour(61) {
+		t.Error("Expected false")
+	}
+
+	if !bucket.Pour(10) {
+		t.Error("Expected true")
+	}
+
+	if !bucket.Pour(49) {
+		t.Error("Expected true")
+	}
+
+	if bucket.Pour(2) {
+		t.Error("Expected false")
+	}
+
+	bucket.Now = func() time.Time { return time.Unix(61, 0) }
+	if !bucket.Pour(60) {
+		t.Error("Expected true")
+	}
+
+	if bucket.Pour(1) {
+		t.Error("Expected false")
+	}
+
+	bucket.Now = func() time.Time { return time.Unix(70, 0) }
+
+	if !bucket.Pour(1) {
+		t.Error("Expected true")
+	}
+
+}
+
+func TestTimeSinceLastUpdate(t *testing.T) {
+	bucket := NewLeakyBucket(60, time.Second)
+	bucket.Now = func() time.Time { return time.Unix(1, 0) }
+	bucket.Pour(1)
+	bucket.Now = func() time.Time { return time.Unix(2, 0) }
+
+	sinceLast := bucket.TimeSinceLastUpdate()
+	if sinceLast != time.Second*1 {
+		t.Errorf("Expected time since last update to be less than 1 second, got %d", sinceLast)
+	}
+}
+
+func TestTimeToDrain(t *testing.T) {
+	bucket := NewLeakyBucket(60, time.Second)
+	bucket.Now = func() time.Time { return time.Unix(1, 0) }
+	bucket.Pour(10)
+
+	if bucket.TimeToDrain() != time.Second*10 {
+		t.Error("Time to drain should be 10 seconds")
+	}
+
+	bucket.Now = func() time.Time { return time.Unix(2, 0) }
+
+	if bucket.TimeToDrain() != time.Second*9 {
+		t.Error("Time to drain should be 9 seconds")
+	}
+}

ratelimiter/memory.go

@@ -0,0 +1,58 @@
+package ratelimiter
+
+import (
+	"errors"
+	"time"
+)
+
+const GC_SIZE int = 100
+
+type Memory struct {
+	store           map[string]LeakyBucket
+	lastGCCollected time.Time
+}
+
+func NewMemory() *Memory {
+	m := new(Memory)
+	m.store = make(map[string]LeakyBucket)
+	m.lastGCCollected = time.Now()
+	return m
+}
+
+func (m *Memory) GetBucketFor(key string) (*LeakyBucket, error) {
+
+	bucket, ok := m.store[key]
+	if !ok {
+		return nil, errors.New("miss")
+	}
+
+	return &bucket, nil
+}
+
+func (m *Memory) SetBucketFor(key string, bucket LeakyBucket) error {
+
+	if len(m.store) > GC_SIZE {
+		m.GarbageCollect()
+	}
+
+	m.store[key] = bucket
+
+	return nil
+}
+
+func (m *Memory) GarbageCollect() {
+	now := time.Now()
+
+	// rate limit GC to once per minute
+	if now.Add(60*time.Second).Unix() > m.lastGCCollected.Unix() {
+
+		for key, bucket := range m.store {
+			// if the bucket is drained, then GC
+			if bucket.DrainedAt().Unix() > now.Unix() {
+				delete(m.store, key)
+			}
+		}
+
+		m.lastGCCollected = now
+	}
+}

ratelimiter/storage.go

@@ -0,0 +1,6 @@
+package ratelimiter
+
+type Storage interface {
+	GetBucketFor(string) (*LeakyBucket, error)
+	SetBucketFor(string, LeakyBucket) error
+}

tail.go

@@ -5,6 +5,7 @@ package tail
 import (
 	"bufio"
 	"fmt"
+	"github.com/ActiveState/tail/ratelimiter"
 	"github.com/ActiveState/tail/util"
 	"github.com/ActiveState/tail/watch"
 	"io"
@@ -39,11 +40,11 @@ type SeekInfo struct {
 // Config is used to specify how a file must be tailed.
 type Config struct {
 	// File-specifc
-	Location  *SeekInfo // Seek to this location before tailing
-	ReOpen    bool      // Reopen recreated files (tail -F)
-	MustExist bool      // Fail early if the file does not exist
-	Poll      bool      // Poll for file changes instead of using inotify
-	LimitRate int64     // Maximum read rate (lines per second)
+	Location    *SeekInfo // Seek to this location before tailing
+	ReOpen      bool      // Reopen recreated files (tail -F)
+	MustExist   bool      // Fail early if the file does not exist
+	Poll        bool      // Poll for file changes instead of using inotify
+	RateLimiter *ratelimiter.LeakyBucket
 
 	// Generic IO
 	Follow      bool // Continue looking for new lines (tail -f)
@@ -63,7 +64,6 @@ type Tail struct {
 	reader  *bufio.Reader
 	watcher watch.FileWatcher
 	changes *watch.FileChanges
-	rateMon *RateMonitor
 
 	tomb.Tomb // provides: Done, Kill, Dying
 }
@@ -95,8 +95,6 @@ func TailFile(filename string, config Config) (*Tail, error) {
 		t.Logger = log.New(os.Stderr, "", log.LstdFlags)
 	}
 
-	t.rateMon = new(RateMonitor)
-
 	if t.Poll {
 		t.watcher = watch.NewPollingFileWatcher(filename)
 	} else {
@@ -222,9 +220,8 @@ func (tail *Tail) tailFileSync() {
 					// Wait a second before seeking till the end of
 					// file when rate limit is reached.
 					msg := fmt.Sprintf(
-						"Too much log activity (more than %d lines "+
-							"per second being written); waiting a second "+
-							"before resuming tailing", tail.LimitRate)
+						"Too much log activity; waiting a second " +
+							"before resuming tailing")
 					tail.Lines <- &Line{msg, time.Now(), fmt.Errorf(msg)}
 					select {
 					case <-time.After(time.Second):
@@ -333,7 +330,6 @@ func (tail *Tail) seekEnd() error {
 // if necessary. Return false if rate limit is reached.
 func (tail *Tail) sendLine(line []byte) bool {
 	now := time.Now()
-	nowUnix := now.Unix()
 	lines := []string{string(line)}
 
 	// Split longer lines
@@ -344,11 +340,12 @@ func (tail *Tail) sendLine(line []byte) bool {
 
 	for _, line := range lines {
 		tail.Lines <- &Line{line, now, nil}
-		rate := tail.rateMon.Tick(nowUnix)
-		if tail.LimitRate > 0 && rate > tail.LimitRate {
-			tail.Logger.Printf("Rate limit (%v < %v) reached on file (%v); entering 1s cooloff period.\n",
-				tail.LimitRate,
-				rate,
+	}
+
+	if tail.Config.RateLimiter != nil {
+		ok := tail.Config.RateLimiter.Pour(uint16(len(lines)))
+		if !ok {
+			tail.Logger.Printf("Leaky bucket full (%v); entering 1s cooloff period.\n",
 				tail.Filename)
 			return false
 		}

tail_test.go

@@ -8,6 +8,7 @@ package tail
 import (
 	"./watch"
 	_ "fmt"
+	"github.com/ActiveState/tail/ratelimiter"
 	"io/ioutil"
 	"os"
 	"strings"
@@ -261,15 +262,17 @@ func TestRateLimiting(_t *testing.T) {
 	t := NewTailTest("rate-limiting", _t)
 	t.CreateFile("test.txt", "hello\nworld\nagain\nextra\n")
 	config := Config{
-		Follow:    true,
-		LimitRate: 2}
-	expecting := "Too much log activity (more than 2 lines per second being written); waiting a second before resuming tailing"
+		Follow:      true,
+		RateLimiter: ratelimiter.NewLeakyBucket(2, time.Second)}
+	leakybucketFull := "Too much log activity; waiting a second before resuming tailing"
 	tail := t.StartTail("test.txt", config)
 
 	// TODO: also verify that tail resumes after the cooloff period.
-	go t.VerifyTailOutput(
-		tail,
-		[]string{"hello", "world", "again", expecting, "more", "data"})
+	go t.VerifyTailOutput(tail, []string{
+		"hello", "world", "again",
+		leakybucketFull,
+		"more", "data",
+		leakybucketFull})
 
 	// Add more data only after reasonable delay.
 	<-time.After(1200 * time.Millisecond)