Add data track data channel #987
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,135 @@ | ||
| // Copyright 2026 LiveKit, Inc. | ||
| // | ||
| // 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. | ||
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| package lksdk | ||
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| import ( | ||
| "sync" | ||
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| protoLogger "github.com/livekit/protocol/logger" | ||
| "github.com/pion/webrtc/v4" | ||
| ) | ||
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| const dataTrackBufferedAmountLowThreshold = 8 * 1024 | ||
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| // dataTrackFramePackets is one frame serialized into data track packets. | ||
| type dataTrackFramePackets [][]byte | ||
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| // dataTrackSender paces frames onto the data track channel, keeping only the freshest frame | ||
| // while the channel's send buffer is above the low threshold. | ||
| type dataTrackSender struct { | ||
| log protoLogger.Logger | ||
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| lock sync.Mutex | ||
| dc *webrtc.DataChannel | ||
| frame dataTrackFramePackets | ||
| notify chan struct{} | ||
| done chan struct{} | ||
| } | ||
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| func newDataTrackSender(log protoLogger.Logger) *dataTrackSender { | ||
| s := &dataTrackSender{ | ||
| log: log, | ||
| notify: make(chan struct{}, 1), | ||
| done: make(chan struct{}), | ||
| } | ||
| go s.run() | ||
| return s | ||
| } | ||
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| // setDataChannel points the sender at the channel it should write to. | ||
| func (s *dataTrackSender) setDataChannel(dc *webrtc.DataChannel) { | ||
| s.lock.Lock() | ||
| s.dc = dc | ||
| s.lock.Unlock() | ||
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| s.wake() | ||
| } | ||
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| func (s *dataTrackSender) setLogger(log protoLogger.Logger) { | ||
| s.log = log | ||
| } | ||
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| func (s *dataTrackSender) send(frame dataTrackFramePackets) { | ||
| if dropped := s.push(frame); dropped != nil { | ||
| s.log.Debugw("dropping data track frame", "numPackets", len(dropped)) | ||
| } | ||
| } | ||
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| func (s *dataTrackSender) wake() { | ||
| select { | ||
| case s.notify <- struct{}{}: | ||
| default: | ||
| } | ||
| } | ||
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| func (s *dataTrackSender) stop() { | ||
| close(s.done) | ||
| } | ||
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| func (s *dataTrackSender) push(frame dataTrackFramePackets) (dropped dataTrackFramePackets) { | ||
| if len(frame) == 0 { | ||
| return nil | ||
| } | ||
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| s.lock.Lock() | ||
| dropped, s.frame = s.frame, frame | ||
| s.lock.Unlock() | ||
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| s.wake() | ||
| return dropped | ||
| } | ||
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| func (s *dataTrackSender) pop() dataTrackFramePackets { | ||
| s.lock.Lock() | ||
| defer s.lock.Unlock() | ||
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| frame := s.frame | ||
| s.frame = nil | ||
| return frame | ||
| } | ||
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| func (s *dataTrackSender) run() { | ||
| var ( | ||
| dc *webrtc.DataChannel | ||
| inFlight dataTrackFramePackets | ||
| ) | ||
| for { | ||
| select { | ||
| case <-s.done: | ||
| return | ||
| case <-s.notify: | ||
| } | ||
|
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| s.lock.Lock() | ||
| current := s.dc | ||
| s.lock.Unlock() | ||
| if current != dc { | ||
| // A partially sent frame cannot be completed on a new channel. | ||
| dc, inFlight = current, nil | ||
| } | ||
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| for dc != nil && dc.ReadyState() == webrtc.DataChannelStateOpen && dc.BufferedAmount() <= dataTrackBufferedAmountLowThreshold { | ||
| if len(inFlight) == 0 { | ||
| if inFlight = s.pop(); inFlight == nil { | ||
| break | ||
| } | ||
| } | ||
| if err := dc.Send(inFlight[0]); err != nil { | ||
| s.log.Debugw("could not send data track packet", "error", err) | ||
| } | ||
| inFlight = inFlight[1:] | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,55 @@ | ||
| // Copyright 2026 LiveKit, Inc. | ||
| // | ||
| // 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. | ||
|
|
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| package lksdk | ||
|
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| import ( | ||
| "testing" | ||
|
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| "github.com/stretchr/testify/require" | ||
| ) | ||
|
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| func testFrame(marker byte, packets int) dataTrackFramePackets { | ||
| frame := make(dataTrackFramePackets, packets) | ||
| for i := range frame { | ||
| frame[i] = []byte{marker, byte(i)} | ||
| } | ||
| return frame | ||
| } | ||
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| func TestDataTrackSenderQueue(t *testing.T) { | ||
| s := newDataTrackSender(logger) | ||
| t.Cleanup(s.stop) | ||
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| require.Nil(t, s.push(nil)) | ||
| require.Nil(t, s.pop()) | ||
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| multi := testFrame(0xaa, 13) | ||
| require.Nil(t, s.push(multi)) | ||
| require.Equal(t, multi, s.pop()) | ||
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| older, newer := testFrame(0x01, 4), testFrame(0x02, 3) | ||
| require.Nil(t, s.push(older)) | ||
| require.Equal(t, older, s.push(newer)) | ||
| require.Equal(t, newer, s.pop()) | ||
| require.Nil(t, s.pop()) | ||
| } | ||
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| func TestSendDataTrackFrameKeepsFreshest(t *testing.T) { | ||
| engine := newTestEngine(t) | ||
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| engine.sendDataTrackFrame(testFrame(0x01, 2)) | ||
| engine.sendDataTrackFrame(testFrame(0x02, 2)) | ||
| require.Equal(t, testFrame(0x02, 2), engine.dataTrackSender.pop()) | ||
| } |
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🟡 Channel replacement sends stale frames
When
setDataChannelreplaces the channel during an active send loop,runcontinues writing the current frame to the old channel. It snapshotsdconly before the inner loop. Packets can reach the obsolete session or be discarded.Prompt for agents
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