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listener.go
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listener.go
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// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this 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 trafficshape
import (
"io"
"net"
"sort"
"sync"
"time"
"github.com/google/martian/log"
)
// ErrForceClose is an error that communicates the need to close the connection.
type ErrForceClose struct {
message string
}
func (efc *ErrForceClose) Error() string {
return efc.message
}
// DefaultBitrate represents the bitrate that will be for all url regexs for which a shape
// has not been specified.
var DefaultBitrate int64 = 500000000000 // 500Gbps (unlimited)
// urlShape contains a rw lock protected shape of a url_regex.
type urlShape struct {
sync.RWMutex
Shape *Shape
}
// urlShapes contains a rw lock protected map of url regexs to their URLShapes.
type urlShapes struct {
sync.RWMutex
M map[string]*urlShape
LastModifiedTime time.Time
}
// Buckets contains the read and write buckets for a url_regex.
type Buckets struct {
ReadBucket *Bucket
WriteBucket *Bucket
}
// NewBuckets returns a *Buckets with the specified up and down bandwidths.
func NewBuckets(up int64, down int64) *Buckets {
return &Buckets{
ReadBucket: NewBucket(up, time.Second),
WriteBucket: NewBucket(down, time.Second),
}
}
// ThrottleContext represents whether we are currently in a throttle interval for a particular
// url_regex. If ThrottleNow is true, only then will the current throttle 'Bandwidth' be set
// correctly.
type ThrottleContext struct {
ThrottleNow bool
Bandwidth int64
}
// NextActionInfo represents whether there is an upcoming action. Only if ActionNext is true will the
// Index and ByteOffset be set correctly.
type NextActionInfo struct {
ActionNext bool
Index int64
ByteOffset int64
}
// Context represents the current information that is needed while writing back to the client.
// Only if Shaping is true, that is we are currently writing back a response that matches a certain
// url_regex will the other values be set correctly. If so, the Buckets represent the buckets
// to be used for the current url_regex. NextActionInfo tells us whether there is an upcoming action
// that needs to be performed, and ThrottleContext tells us whether we are currently in a throttle
// interval (according to the RangeStart). Note, the ThrottleContext is only used once in the start
// to determine the beginning bandwidth. It need not be updated after that. This
// is because the subsequent throttles are captured in the upcoming ChangeBandwidth actions.
// Byte Offset represents the absolute byte offset of response data that we are currently writing back.
// It does not account for the header data.
type Context struct {
Shaping bool
RangeStart int64
URLRegex string
Buckets *Buckets
GlobalBucket *Bucket
ThrottleContext *ThrottleContext
NextActionInfo *NextActionInfo
ByteOffset int64
HeaderLen int64
HeaderBytesWritten int64
}
// Listener wraps a net.Listener and simulates connection latency and bandwidth
// constraints.
type Listener struct {
net.Listener
ReadBucket *Bucket
WriteBucket *Bucket
mu sync.RWMutex
latency time.Duration
GlobalBuckets map[string]*Bucket
Shapes *urlShapes
defaults *Default
}
// Conn wraps a net.Conn and simulates connection latency and bandwidth
// constraints. Shapes represents the traffic shape map inherited from the listener.
// Established is the time that this connection was established. LocalBuckets represents a map from
// the url_regexes to their dedicated buckets.
type Conn struct {
net.Conn
ReadBucket *Bucket // Shared by listener.
WriteBucket *Bucket // Shared by listener.
latency time.Duration
ronce sync.Once
wonce sync.Once
Shapes *urlShapes
GlobalBuckets map[string]*Bucket
LocalBuckets map[string]*Buckets
Established time.Time
Context *Context
DefaultBandwidth Bandwidth
Listener *Listener
}
// NewListener returns a new bandwidth constrained listener. Defaults to
// DefaultBitrate (uncapped).
func NewListener(l net.Listener) *Listener {
return &Listener{
Listener: l,
ReadBucket: NewBucket(DefaultBitrate/8, time.Second),
WriteBucket: NewBucket(DefaultBitrate/8, time.Second),
Shapes: &urlShapes{M: make(map[string]*urlShape)},
GlobalBuckets: make(map[string]*Bucket),
defaults: &Default{
Bandwidth: Bandwidth{
Up: DefaultBitrate / 8,
Down: DefaultBitrate / 8,
},
Latency: 0,
},
}
}
// ReadBitrate returns the bitrate in bits per second for reads.
func (l *Listener) ReadBitrate() int64 {
return l.ReadBucket.Capacity() * 8
}
// SetReadBitrate sets the bitrate in bits per second for reads.
func (l *Listener) SetReadBitrate(bitrate int64) {
l.ReadBucket.SetCapacity(bitrate / 8)
}
// WriteBitrate returns the bitrate in bits per second for writes.
func (l *Listener) WriteBitrate() int64 {
return l.WriteBucket.Capacity() * 8
}
// SetWriteBitrate sets the bitrate in bits per second for writes.
func (l *Listener) SetWriteBitrate(bitrate int64) {
l.WriteBucket.SetCapacity(bitrate / 8)
}
// SetDefaults sets the default traffic shaping parameters for the listener.
func (l *Listener) SetDefaults(defaults *Default) {
l.mu.Lock()
defer l.mu.Unlock()
l.defaults = defaults
}
// Defaults returns the default traffic shaping parameters for the listener.
func (l *Listener) Defaults() *Default {
l.mu.RLock()
defer l.mu.RUnlock()
return l.defaults
}
// Latency returns the latency for connections.
func (l *Listener) Latency() time.Duration {
l.mu.Lock()
defer l.mu.Unlock()
return l.latency
}
// SetLatency sets the initial latency for connections.
func (l *Listener) SetLatency(latency time.Duration) {
l.mu.Lock()
defer l.mu.Unlock()
l.latency = latency
}
// GetTrafficShapedConn takes in a normal connection and returns a traffic shaped connection.
func (l *Listener) GetTrafficShapedConn(oc net.Conn) *Conn {
if tsconn, ok := oc.(*Conn); ok {
return tsconn
}
urlbuckets := make(map[string]*Buckets)
globalurlbuckets := make(map[string]*Bucket)
l.Shapes.RLock()
defaults := l.Defaults()
latency := l.Latency()
defaultBandwidth := defaults.Bandwidth
for regex, shape := range l.Shapes.M {
// It should be ok to not acquire the read lock on shape, since WriteBucket is never mutated.
globalurlbuckets[regex] = shape.Shape.WriteBucket
urlbuckets[regex] = NewBuckets(DefaultBitrate/8, shape.Shape.MaxBandwidth)
}
l.Shapes.RUnlock()
curinfo := &Context{}
lc := &Conn{
Conn: oc,
latency: latency,
ReadBucket: l.ReadBucket,
WriteBucket: l.WriteBucket,
Shapes: l.Shapes,
GlobalBuckets: globalurlbuckets,
LocalBuckets: urlbuckets,
Context: curinfo,
Established: time.Now(),
DefaultBandwidth: defaultBandwidth,
Listener: l,
}
return lc
}
// Accept waits for and returns the next connection to the listener.
func (l *Listener) Accept() (net.Conn, error) {
oc, err := l.Listener.Accept()
if err != nil {
log.Errorf("trafficshape: failed accepting connection: %v", err)
return nil, err
}
if tconn, ok := oc.(*net.TCPConn); ok {
log.Debugf("trafficshape: setting keep-alive for TCP connection")
tconn.SetKeepAlive(true)
tconn.SetKeepAlivePeriod(3 * time.Minute)
}
return l.GetTrafficShapedConn(oc), nil
}
// Close closes the read and write buckets along with the underlying listener.
func (l *Listener) Close() error {
defer log.Debugf("trafficshape: closed read/write buckets and connection")
l.ReadBucket.Close()
l.WriteBucket.Close()
return l.Listener.Close()
}
// Read reads bytes from connection into b, optionally simulating connection
// latency and throttling read throughput based on desired bandwidth
// constraints.
func (c *Conn) Read(b []byte) (int, error) {
c.ronce.Do(c.sleepLatency)
n, err := c.ReadBucket.FillThrottle(func(remaining int64) (int64, error) {
max := remaining
if l := int64(len(b)); max > l {
max = l
}
n, err := c.Conn.Read(b[:max])
return int64(n), err
})
if err != nil && err != io.EOF {
log.Errorf("trafficshape: error on throttled read: %v", err)
}
return int(n), err
}
// ReadFrom reads data from r until EOF or error, optionally simulating
// connection latency and throttling read throughput based on desired bandwidth
// constraints.
func (c *Conn) ReadFrom(r io.Reader) (int64, error) {
c.ronce.Do(c.sleepLatency)
var total int64
for {
n, err := c.ReadBucket.FillThrottle(func(remaining int64) (int64, error) {
return io.CopyN(c.Conn, r, remaining)
})
total += n
if err == io.EOF {
log.Debugf("trafficshape: exhausted reader successfully")
return total, nil
} else if err != nil {
log.Errorf("trafficshape: failed copying from reader: %v", err)
return total, err
}
}
}
// WriteTo writes data to w from the connection, optionally simulating
// connection latency and throttling write throughput based on desired
// bandwidth constraints.
func (c *Conn) WriteTo(w io.Writer) (int64, error) {
c.wonce.Do(c.sleepLatency)
var total int64
for {
n, err := c.WriteBucket.FillThrottle(func(remaining int64) (int64, error) {
return io.CopyN(w, c.Conn, remaining)
})
total += n
if err != nil {
if err != io.EOF {
log.Errorf("trafficshape: failed copying to writer: %v", err)
}
return total, err
}
}
}
func min(x, y int64) int64 {
if x < y {
return x
}
return y
}
// CheckExistenceAndValidity checks that the current url regex is present in the map, and that
// the connection was established before the url shape map was last updated. We do not allow the
// updated url shape map to traffic shape older connections.
// Important: Assumes you have acquired the required locks and will release them youself.
func (c *Conn) CheckExistenceAndValidity(URLRegex string) bool {
shapeStillValid := c.Shapes.LastModifiedTime.Before(c.Established)
_, p := c.Shapes.M[URLRegex]
return p && shapeStillValid
}
// GetCurrentThrottle uses binary search to determine if the current byte offset ('start')
// lies within a throttle interval. If so, also returns the bandwidth specified for that interval.
func (c *Conn) GetCurrentThrottle(start int64) *ThrottleContext {
c.Shapes.RLock()
defer c.Shapes.RUnlock()
if !c.CheckExistenceAndValidity(c.Context.URLRegex) {
log.Debugf("existence check failed")
return &ThrottleContext{
ThrottleNow: false,
}
}
c.Shapes.M[c.Context.URLRegex].RLock()
defer c.Shapes.M[c.Context.URLRegex].RUnlock()
throttles := c.Shapes.M[c.Context.URLRegex].Shape.Throttles
if l := len(throttles); l != 0 {
// ind is the first index in throttles with ByteStart > start.
// Once we get ind, we can check the previous throttle, if any,
// to see if its ByteEnd is after 'start'.
ind := sort.Search(len(throttles),
func(i int) bool { return throttles[i].ByteStart > start })
// All throttles have Bytestart > start, hence not in throttle.
if ind == 0 {
return &ThrottleContext{
ThrottleNow: false,
}
}
// No throttle has Bytestart > start, so check the last throttle to
// see if it ends after 'start'. Note: the last throttle is special
// since it can have -1 (meaning infinity) as the ByteEnd.
if ind == l {
if throttles[l-1].ByteEnd > start || throttles[l-1].ByteEnd == -1 {
return &ThrottleContext{
ThrottleNow: true,
Bandwidth: throttles[l-1].Bandwidth,
}
}
return &ThrottleContext{
ThrottleNow: false,
}
}
// Check the previous throttle to see if it ends after 'start'.
if throttles[ind-1].ByteEnd > start {
return &ThrottleContext{
ThrottleNow: true,
Bandwidth: throttles[ind-1].Bandwidth,
}
}
return &ThrottleContext{
ThrottleNow: false,
}
}
return &ThrottleContext{
ThrottleNow: false,
}
}
// GetNextActionFromByte takes in a byte offset and uses binary search to determine the upcoming
// action, i.e the first action after the byte that still has a non zero count.
func (c *Conn) GetNextActionFromByte(start int64) *NextActionInfo {
c.Shapes.RLock()
defer c.Shapes.RUnlock()
if !c.CheckExistenceAndValidity(c.Context.URLRegex) {
log.Debugf("existence check failed")
return &NextActionInfo{
ActionNext: false,
}
}
c.Shapes.M[c.Context.URLRegex].RLock()
defer c.Shapes.M[c.Context.URLRegex].RUnlock()
actions := c.Shapes.M[c.Context.URLRegex].Shape.Actions
if l := len(actions); l != 0 {
ind := sort.Search(len(actions),
func(i int) bool { return actions[i].getByte() >= start })
return c.GetNextActionFromIndex(int64(ind))
}
return &NextActionInfo{
ActionNext: false,
}
}
// GetNextActionFromIndex takes in an index and returns the first action after the index that
// has a non zero count, if there is one.
func (c *Conn) GetNextActionFromIndex(ind int64) *NextActionInfo {
c.Shapes.RLock()
defer c.Shapes.RUnlock()
if !c.CheckExistenceAndValidity(c.Context.URLRegex) {
return &NextActionInfo{
ActionNext: false,
}
}
c.Shapes.M[c.Context.URLRegex].RLock()
defer c.Shapes.M[c.Context.URLRegex].RUnlock()
actions := c.Shapes.M[c.Context.URLRegex].Shape.Actions
if l := int64(len(actions)); l != 0 {
for ind < l && (actions[ind].getCount() == 0) {
ind++
}
if ind >= l {
return &NextActionInfo{
ActionNext: false,
}
}
return &NextActionInfo{
ActionNext: true,
Index: ind,
ByteOffset: actions[ind].getByte(),
}
}
return &NextActionInfo{
ActionNext: false,
}
}
// WriteDefaultBuckets writes bytes from b to the connection, optionally simulating
// connection latency and throttling write throughput based on desired
// bandwidth constraints. It uses the WriteBucket inherited from the listener.
func (c *Conn) WriteDefaultBuckets(b []byte) (int, error) {
c.wonce.Do(c.sleepLatency)
var total int64
for len(b) > 0 {
var max int64
n, err := c.WriteBucket.FillThrottle(func(remaining int64) (int64, error) {
max = remaining
if l := int64(len(b)); remaining >= l {
max = l
}
n, err := c.Conn.Write(b[:max])
return int64(n), err
})
total += n
if err != nil {
if err != io.EOF {
log.Errorf("trafficshape: failed write: %v", err)
}
return int(total), err
}
b = b[max:]
}
return int(total), nil
}
// Write writes bytes from b to the connection, while enforcing throttles and performing actions.
// It uses and updates the Context in the connection.
func (c *Conn) Write(b []byte) (int, error) {
if !c.Context.Shaping {
return c.WriteDefaultBuckets(b)
}
c.wonce.Do(c.sleepLatency)
var total int64
// Write the header if needed, without enforcing any traffic shaping, and without updating
// ByteOffset.
if headerToWrite := c.Context.HeaderLen - c.Context.HeaderBytesWritten; headerToWrite > 0 {
writeAmount := min(int64(len(b)), headerToWrite)
n, err := c.Conn.Write(b[:writeAmount])
if err != nil {
if err != io.EOF {
log.Errorf("trafficshape: failed write: %v", err)
}
return int(n), err
}
c.Context.HeaderBytesWritten += writeAmount
total += writeAmount
b = b[writeAmount:]
}
var amountToWrite int64
for len(b) > 0 {
var max int64
// Determine the amount to be written up till the next action.
amountToWrite = int64(len(b))
if c.Context.NextActionInfo.ActionNext {
amountTillNextAction := c.Context.NextActionInfo.ByteOffset - c.Context.ByteOffset
if amountTillNextAction <= amountToWrite {
amountToWrite = amountTillNextAction
}
}
// Write into both the local and global buckets, as well as the underlying connection.
n, err := c.Context.Buckets.WriteBucket.FillThrottleLocked(func(remaining int64) (int64, error) {
max = min(remaining, amountToWrite)
if max == 0 {
return 0, nil
}
return c.Context.GlobalBucket.FillThrottleLocked(func(rem int64) (int64, error) {
max = min(rem, max)
n, err := c.Conn.Write(b[:max])
return int64(n), err
})
})
if err != nil {
if err != io.EOF {
log.Errorf("trafficshape: failed write: %v", err)
}
return int(total), err
}
// Update the current byte offset.
c.Context.ByteOffset += n
total += n
b = b[max:]
// Check if there was an upcoming action, and that the byte offset matches the action's byte.
if c.Context.NextActionInfo.ActionNext &&
c.Context.ByteOffset >= c.Context.NextActionInfo.ByteOffset {
// Note here, we check again that the url shape map is still valid and that the action still has
// a non zero count, since that could have been modified since the last time we checked.
ind := c.Context.NextActionInfo.Index
c.Shapes.RLock()
if !c.CheckExistenceAndValidity(c.Context.URLRegex) {
c.Shapes.RUnlock()
// Write the remaining b using default buckets, and set Shaping as false
// so that subsequent calls to Write() also use default buckets
// without performing any actions.
c.Context.Shaping = false
writeTotal, e := c.WriteDefaultBuckets(b)
return int(total) + writeTotal, e
}
c.Shapes.M[c.Context.URLRegex].Lock()
actions := c.Shapes.M[c.Context.URLRegex].Shape.Actions
if actions[ind].getCount() != 0 {
// Update the action count, determine the type of action and perform it.
actions[ind].decrementCount()
switch action := actions[ind].(type) {
case *Halt:
d := action.Duration
log.Debugf("trafficshape: Sleeping for time %d ms for urlregex %s at byte offset %d",
d, c.Context.URLRegex, c.Context.ByteOffset)
c.Shapes.M[c.Context.URLRegex].Unlock()
c.Shapes.RUnlock()
time.Sleep(time.Duration(d) * time.Millisecond)
case *CloseConnection:
log.Infof("trafficshape: Closing connection for urlregex %s at byte offset %d",
c.Context.URLRegex, c.Context.ByteOffset)
c.Shapes.M[c.Context.URLRegex].Unlock()
c.Shapes.RUnlock()
return int(total), &ErrForceClose{message: "Forcing close connection"}
case *ChangeBandwidth:
bw := action.Bandwidth
log.Infof("trafficshape: Changing connection bandwidth to %d for urlregex %s at byte offset %d",
bw, c.Context.URLRegex, c.Context.ByteOffset)
c.Shapes.M[c.Context.URLRegex].Unlock()
c.Shapes.RUnlock()
c.Context.Buckets.WriteBucket.SetCapacity(bw)
default:
c.Shapes.M[c.Context.URLRegex].Unlock()
c.Shapes.RUnlock()
}
} else {
c.Shapes.M[c.Context.URLRegex].Unlock()
c.Shapes.RUnlock()
}
// Get the next action to be performed, if any.
c.Context.NextActionInfo = c.GetNextActionFromIndex(ind + 1)
}
}
return int(total), nil
}
func (c *Conn) sleepLatency() {
log.Debugf("trafficshape: simulating latency: %s", c.latency)
time.Sleep(c.latency)
}