-
Notifications
You must be signed in to change notification settings - Fork 56
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
NetworkConditioner allows to replicate in a predictable way network condition, such as a 3G or LTE network. There is a list of pre-defined NetworkConditionerPreset, or the user can provided their own.
- Loading branch information
Showing
6 changed files
with
540 additions
and
9 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,132 @@ | ||
| package vnet | ||
|
|
||
| import ( | ||
| "math/rand" | ||
| "sync/atomic" | ||
| "time" | ||
| "unsafe" | ||
| ) | ||
|
|
||
| const ( | ||
| // NetworkConditionPacketLossDenominator is the denominator by which the `NetworkCondition.PacketLoss` value | ||
| // will be divided. | ||
| NetworkConditionPacketLossDenominator uint32 = 1000 | ||
|
|
||
| kiloBytesInBytes = 1000 | ||
| // Value chosen arbitrarily, there may be a better one. | ||
| bandwidthComputeThreshold = 2 * time.Second | ||
| ) | ||
|
|
||
| // NetworkConditioner hold the NetworkCondition of DownLink and UpLink channels. | ||
| type NetworkConditioner struct { | ||
| // Internals stats | ||
|
|
||
| // Total of downLink bytes | ||
| // Must be accessed atomically. | ||
| inBytes uint64 | ||
| pendingInBytes uint64 | ||
| lastInByteChunkTimestamp int64 | ||
|
|
||
| // Total of upLink bytes | ||
| // Must be accessed atomically. | ||
| outBytes uint64 | ||
| pendingOutBytes uint64 | ||
| lastOutByteChunkTimestamp int64 | ||
|
|
||
| // DownLink represents the DownLink condition. | ||
| DownLink NetworkCondition | ||
| // UpLink represents the UpLink condition. | ||
| UpLink NetworkCondition | ||
| } | ||
|
|
||
| func (n *NetworkConditioner) handleDownLink(c Chunk) bool { | ||
| atomic.AddUint64(&n.pendingInBytes, uint64(len(c.UserData()))) | ||
|
|
||
| bandwidthLimiterSleep := n.bandwidthLimiter(&n.DownLink.MaxBandwidth, &n.lastInByteChunkTimestamp, &n.inBytes, &n.pendingInBytes) | ||
|
|
||
| // Apply constant latency if required | ||
| if sleepNeeded := time.Duration(atomic.LoadInt64((*int64)(&n.DownLink.Latency))) - bandwidthLimiterSleep; sleepNeeded > 0 { | ||
| time.Sleep(sleepNeeded) | ||
| } | ||
|
|
||
| return n.DownLink.shouldDropPacket() | ||
| } | ||
|
|
||
| func (n *NetworkConditioner) handleUpLink(c Chunk) bool { | ||
| atomic.AddUint64(&n.pendingOutBytes, uint64(len(c.UserData()))) | ||
|
|
||
| bandwidthLimiterSleep := n.bandwidthLimiter(&n.UpLink.MaxBandwidth, &n.lastOutByteChunkTimestamp, &n.outBytes, &n.pendingOutBytes) | ||
|
|
||
| // Apply constant latency if required | ||
| if sleepNeeded := time.Duration(atomic.LoadInt64((*int64)(&n.UpLink.Latency))) - bandwidthLimiterSleep; sleepNeeded > 0 { | ||
| time.Sleep(sleepNeeded) | ||
| } | ||
|
|
||
| return n.UpLink.shouldDropPacket() | ||
| } | ||
|
|
||
| func (n *NetworkConditioner) bandwidthLimiter(maxBandwidth **uint32, lastTimestamp *int64, totalBytes *uint64, pendingBytes *uint64) time.Duration { | ||
| // Is safe because refers to a `MaxBandwidth` field in an initialized NetworkCondition struct. | ||
| // nolint:gosec | ||
| bandwidthLimit := (*uint32)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(maxBandwidth)))) | ||
| bandwidthLimiterSleep := 0 * time.Millisecond | ||
|
|
||
| if bandwidthLimit != nil { | ||
| now := time.Now().UnixNano() | ||
| isFirstLoop := atomic.CompareAndSwapInt64(lastTimestamp, 0, now) | ||
|
|
||
| if !isFirstLoop { | ||
| duration := now - atomic.LoadInt64(lastTimestamp) | ||
| if time.Duration(duration) > bandwidthComputeThreshold { | ||
| previouslyPending := atomic.SwapUint64(pendingBytes, 0) | ||
|
|
||
| bandwidthKbps := (float64(previouslyPending) / float64(duration) * float64(time.Second)) / kiloBytesInBytes | ||
|
|
||
| atomic.AddUint64(totalBytes, previouslyPending) | ||
| atomic.StoreInt64(lastTimestamp, now) | ||
|
|
||
| if bandwidthKbps > float64(*bandwidthLimit) { | ||
| exceeding := bandwidthKbps - float64(*bandwidthLimit) | ||
| bandwidthLimiterSleep = time.Duration(exceeding * float64(time.Second)) | ||
|
|
||
| time.Sleep(bandwidthLimiterSleep) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| return bandwidthLimiterSleep | ||
| } | ||
|
|
||
| // NetworkCondition represents the network condition parameter of a data transmission channel direction. | ||
| type NetworkCondition struct { | ||
| // Latency represents the network delay. | ||
| Latency time.Duration | ||
| // MaxBandwidth is the maximum bandwidth, in Kbps. | ||
| MaxBandwidth *uint32 | ||
| // PacketLoss in percentage. | ||
| // This value will be divided by NetworkConditionPacketLossDenominator. | ||
| // Any quotient > 1.00 is meaningless. | ||
| PacketLoss uint32 | ||
| } | ||
|
|
||
| // Updates atomically each member of the current NetworkCondition with the new one. | ||
| func (c *NetworkCondition) update(newCondition NetworkCondition) { | ||
| // Each member is atomically updated, but not the whole struct. | ||
| // This isn't a problem, as it may only affect a few packets – and removes the need for locks. | ||
| // nolint:gosec | ||
| atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&c.MaxBandwidth)), unsafe.Pointer(newCondition.MaxBandwidth)) | ||
| atomic.StoreInt64((*int64)(&c.Latency), int64(newCondition.Latency)) | ||
| atomic.StoreUint32(&c.PacketLoss, newCondition.PacketLoss) | ||
| } | ||
|
|
||
| func (c *NetworkCondition) shouldDropPacket() bool { | ||
| packetLoss := atomic.LoadUint32(&c.PacketLoss) | ||
|
|
||
| // nolint:gosec | ||
| if packetLoss > 0 && uint32(rand.Int31n(int32(NetworkConditionPacketLossDenominator))) < packetLoss { | ||
| return true | ||
| } | ||
|
|
||
| return false | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,26 @@ | ||
| package vnet | ||
|
|
||
| import ( | ||
| "testing" | ||
| ) | ||
|
|
||
| func TestNetworkConditionerPresets(t *testing.T) { | ||
| presets := [...]NetworkConditionerPreset{ | ||
| NetworkConditionerPresetNone, | ||
| NetworkConditionerPresetFullLoss, | ||
| NetworkConditionerPreset3G, | ||
| NetworkConditionerPresetDSL, | ||
| NetworkConditionerPresetEdge, | ||
| NetworkConditionerPresetLTE, | ||
| NetworkConditionerPresetVeryBadNetwork, | ||
| NetworkConditionerPresetWiFi, | ||
| } | ||
|
|
||
| for _, preset := range presets { | ||
| conditioner := NewNetworkConditioner(preset) | ||
|
|
||
| if conditioner == nil { | ||
| t.Fail() | ||
| } | ||
| } | ||
| } |
Oops, something went wrong.