feat: Data Tracks by davidliu · Pull Request #1004 · livekit/client-sdk-android

davidliu · 2026-08-20T16:37:30Z

Adds data track support, sharing the Rust UniFFI core (livekit-uniffi-android) with the other SDKs.
Most of room/datatrack/ is a thin wrapper around that core. The Android-specific work is the WebRTC, signaling, and reconnect glue.
Actual changes

RTCEngine / DataTrackFrameSender — _data_track channel, send backpressure, wait-for-open, reconnect
SignalClient — publish / unpublish / subscriber-handle / request-response forwarding
Room, LocalParticipant, RemoteParticipant — public API, attach/park remote tracks, events
IncomingDataTrackManager / OutgoingDataTrackManager — bridge UniFFI managers to the engine
DataTrackCryptor / E2EEManager — E2EE via the existing data-packet cryptor
DataChannelManager, RTCModule, test DI — channel metering and injectable factories

Simple wrappers (FFI type/API mapping, little Android-specific logic)

LocalDataTrack, RemoteDataTrack, DataTrackStream
DataTrackFrame, DataTrackInfo, DataTrackSid, DataTrackSchema, DataTrackPublishOptions, DataTrackException
DataTrackManagerFactory, IncomingDataTrackEvent

E2E tests: https://github.com/livekit/e2e-android/pull/13

changeset-bot · 2026-08-20T16:37:33Z

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pblazej · 2026-08-27T10:26:58Z

Compared this against the Swift (#975), JS (#1994) and Rust implementations, looking for behavior diffs.

Before merge

DataTrackPublished is dropped, not deferred — Room.kt:905 gates it on emitWhenConnected, but joinImpl attaches tracks while state is CONNECTING/RECONNECTING, so it never fires for tracks present at join or after a full reconnect. DataTrackUnpublished posts directly (:821), so apps can see an Unpublished with no Published. JS deliberately uses plain emit for both; Swift notifies unconditionally.
Data-track init can fail Room.connect — RTCEngine.kt:303 calls handleSfuJoinResponse unguarded and builds the UniFFI manager there on every connect, catching only HandleSignalResponseException. So an UnsatisfiedLinkError fails the connect for apps that never touch data tracks — reachable on API 21–23, where tools:overrideLibrary (AndroidManifest.xml:17) hides that the AAR won't load and nothing gates on SDK_INT. Swift's call is try?. handlePacketReceived has no try/catch at all and runs on a WebRTC thread.
waitUntilInboundDataTrackChannelReady() precedes resendSubscriptionUpdates() — RTCEngine.kt:781. If the SFU opens the subscriber channel in response to a subscription, the wait can't clear until the call after it runs; at best it adds MAX_ICE_CONNECT_TIMEOUT_MS to every full reconnect with remote tracks. Swift, JS and Rust all resubscribe straight after transport connect — suggest deleting the gate. The unit test hand-feeds the channel, so it passes either way.
A dead transport can report CONNECTED — RTCEngine.kt:362 suppresses DISCONNECTED while reconnecting, then the success branch sets CONNECTED unconditionally after up to ~40 s of waiting. An ICE failure in between is swallowed and overwritten, and connectionChangeListener can't cover it because reconnect() early-returns while reconnectingJob is live. Not data-track scoped.

Public surface — cheaper to settle now

DataTrackPublishOptions (:22) allows either field null and never checks compatibility (JsonSchema + Cdr passes locally, fails remotely). Swift uses two constructors, JS validates against COMPATIBLE_SCHEMA_ENCODINGS. A validating factory is additive later, but the permissive constructor is forever. No test covers an invalid pair.
The LocalDataTrack KDoc's "releasing the last reference unpublishes it" is Swift's ARC text — on the JVM the DropGuard waits on the UniFFI Cleaner, so a dropped reference can leave the publication live on the SFU. Nothing is AutoCloseable and close() only clears the map. I'd fix the doc now and let AutoCloseable follow.

Small

RTCEngine.kt:1079 — the observer wrapper captures the old manager while the gate reads the current field, so a stale CLOSED flips an already-open replacement back to WAITING and the next publish burns the full timeout. Swift guards with guard dataChannel === publisherChannel.
IncomingDataTrackManager.kt:62 — the delegate captures its manager and Rust holds it as a JNI global ref, so the cycle spans the FFI boundary and retains the engine and both PCs unless close() runs. Swift split out a weak-holding shim. Same shape in OutgoingDataTrackManager.
SignalClient.kt:745 — unguarded parseFrom inside the UniFFI forward task throws across the boundary; Swift logs and skips.
OutgoingDataTrackManager.kt:78 — startsWith("Timed out") to classify the error; reword RTCEngine.kt:1024/1038 and every timeout silently becomes a disconnect. Two exception types instead.
RTCEngine.kt:1580 — subscribe-only clients negotiate a publisher PC via the shared sendDataTrackSignalRequest; both references keep subscribe signal-only, and the hasPublished guard is redundant (:814).
DataChannelManager.waitUntilOpen() has three tests and no production caller; sendOrQueue's per-frame copyOf() copies already-fresh packets on the RTC thread.

github-actions · 2026-09-07T14:30:53Z

Diffuse output:

Base AAR cache miss. Please run the build job on main to generate the base AAR.

github-actions · 2026-09-07T14:36:14Z

Dependency diff:

 +--- com.squareup.okhttp3:okhttp:4.12.0
|    \--- com.squareup.okio:okio:3.6.0
|         \--- com.squareup.okio:okio-jvm:3.6.0
|              \--- org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.9.10
|                   \--- org.jetbrains.kotlin:kotlin-stdlib:1.9.10 -> 1.9.25
-|                        \--- org.jetbrains:annotations:13.0
+|                        \--- org.jetbrains:annotations:13.0 -> 23.0.0
+--- com.github.davidliu:audioswitch:039a35aefab7747c557242fa216c9ea11743b604
-|    \--- androidx.annotation:annotation:1.3.0 -> 1.7.1
-|         \--- androidx.annotation:annotation-jvm:1.7.1
-|              \--- org.jetbrains.kotlin:kotlin-stdlib:1.7.10 -> 1.9.25 (*)
+|    \--- androidx.annotation:annotation:1.3.0 -> 1.9.0
+|         \--- androidx.annotation:annotation-jvm:1.9.0
+|              \--- org.jetbrains.kotlin:kotlin-stdlib:1.7.10 -> 1.9.25 (*)
-+--- org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.0 -> 1.6.4
-|    +--- org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4
-|    |    \--- org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.6.4
-|    |         +--- org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.6.4
-|    |         |    +--- org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4 (c)
-|    |         |    +--- org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4 (c)
-|    |         |    \--- org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.6.4 (c)
-|    |         +--- org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.6.21 -> 1.9.10 (*)
-|    |         \--- org.jetbrains.kotlin:kotlin-stdlib-common:1.6.21 -> 1.9.25 (*)
-|    +--- org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.6.4 (*)
-|    \--- org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.6.21 -> 1.9.10 (*)
++--- org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.0 -> 1.8.1
+|    +--- org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.1
+|    |    \--- org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.8.1
+|    |         +--- org.jetbrains:annotations:23.0.0
+|    |         +--- org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.8.1
+|    |         |    +--- org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1 (c)
+|    |         |    +--- org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.8.1 (c)
+|    |         |    \--- org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.1 (c)
+|    |         \--- org.jetbrains.kotlin:kotlin-stdlib:1.9.21 -> 1.9.25 (*)
+|    +--- org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.8.1 (*)
+|    \--- org.jetbrains.kotlin:kotlin-stdlib:1.9.21 -> 1.9.25 (*)
-+--- com.auth0.android:jwtdecode:2.0.2
-|    \--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-+--- androidx.annotation:annotation:1.7.1 (*)
-\--- androidx.core:core:1.13.1
-     +--- androidx.annotation:annotation:1.6.0 -> 1.7.1 (*)
-     +--- androidx.collection:collection:1.0.0
-     |    \--- androidx.annotation:annotation:1.0.0 -> 1.7.1 (*)
-     +--- androidx.concurrent:concurrent-futures:1.0.0 -> 1.1.0
-     |    \--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     +--- androidx.interpolator:interpolator:1.0.0
-     |    \--- androidx.annotation:annotation:1.0.0 -> 1.7.1 (*)
-     +--- androidx.lifecycle:lifecycle-runtime:2.6.2
-     |    +--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     |    +--- androidx.arch.core:core-common:2.2.0
-     |    |    \--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     |    +--- androidx.arch.core:core-runtime:2.2.0
-     |    |    \--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     |    +--- androidx.lifecycle:lifecycle-common:2.6.2
-     |    |    +--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     |    |    \--- org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4 (*)
-     |    \--- androidx.profileinstaller:profileinstaller:1.3.0
-     |         +--- androidx.annotation:annotation:1.2.0 -> 1.7.1 (*)
-     |         \--- androidx.startup:startup-runtime:1.1.1
-     |              +--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     |              \--- androidx.tracing:tracing:1.0.0
-     |                   \--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
-     \--- androidx.versionedparcelable:versionedparcelable:1.1.1
-          \--- androidx.annotation:annotation:1.1.0 -> 1.7.1 (*)
++--- io.livekit:livekit-uniffi-android:0.1.9
+|    +--- androidx.annotation:annotation:1.9.0 (*)
+|    +--- net.java.dev.jna:jna:5.16.0
+|    +--- org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.1 (*)
+|    \--- org.jetbrains.kotlin:kotlin-stdlib:1.9.22 -> 1.9.25 (*)
++--- com.auth0.android:jwtdecode:2.0.2
+|    \--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
++--- androidx.annotation:annotation:1.7.1 -> 1.9.0 (*)
+\--- androidx.core:core:1.13.1
+     +--- androidx.annotation:annotation:1.6.0 -> 1.9.0 (*)
+     +--- androidx.collection:collection:1.0.0
+     |    \--- androidx.annotation:annotation:1.0.0 -> 1.9.0 (*)
+     +--- androidx.concurrent:concurrent-futures:1.0.0 -> 1.1.0
+     |    \--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     +--- androidx.interpolator:interpolator:1.0.0
+     |    \--- androidx.annotation:annotation:1.0.0 -> 1.9.0 (*)
+     +--- androidx.lifecycle:lifecycle-runtime:2.6.2
+     |    +--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     |    +--- androidx.arch.core:core-common:2.2.0
+     |    |    \--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     |    +--- androidx.arch.core:core-runtime:2.2.0
+     |    |    \--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     |    +--- androidx.lifecycle:lifecycle-common:2.6.2
+     |    |    +--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     |    |    \--- org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4 -> 1.8.1 (*)
+     |    \--- androidx.profileinstaller:profileinstaller:1.3.0
+     |         +--- androidx.annotation:annotation:1.2.0 -> 1.9.0 (*)
+     |         \--- androidx.startup:startup-runtime:1.1.1
+     |              +--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     |              \--- androidx.tracing:tracing:1.0.0
+     |                   \--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)
+     \--- androidx.versionedparcelable:versionedparcelable:1.1.1
+          \--- androidx.annotation:annotation:1.1.0 -> 1.9.0 (*)

…chema

davidliu · 2026-09-08T07:45:40Z

@pblazej can I get you to recheck?

xianshijing-lk · 2026-09-10T23:13:12Z

Any plan to land this PR soon ? I got pinged by the Robotic team

ladvoc · 2026-09-10T23:22:27Z

+        is Custom -> FfiSchemaEncoding.Custom(identifier)
+    }
+
+    internal fun toProto(): LivekitModels.DataTrackSchemaEncoding {


question: Why does this need to be converted to Protobuf?

xianshijing-lk · 2026-09-11T00:31:31Z

+            if (tracks.values.any { it === track }) {
+                return@synchronized false
+            }
+            tracks = tracks + (track.name to track)


It uses the track.name as the key ? is this correct ? any chance that two tracks from one participant sharing the same name ?

or should we use sid as key ?

xianshijing-lk · 2026-09-11T00:33:46Z

    private var reliableDataChannelSub: DataChannel? = null
    private var lossyDataChannel: DataChannel? = null
    private var lossyDataChannelSub: DataChannel? = null
+    private var dataTrackDataChannelSub: DataChannel? = null


is this dataTrackDataChannelSub needed ? I don't see how it is used rather than assign and clear, is it intentional ?

pblazej · 2026-09-11T07:13:07Z

+ *
+ * @suppress
+ */
+fun interface LocalDataTrackManagerFactory {


These are public but their signatures are io.livekit.uniffi.* types, and that dep is implementation (build.gradle:121) — so consumers can't reference them, or the public constructors taking them, without adding it themselves. @suppress is Dokka-only, so internal is the actual fix; Dagger binds internal types fine within a module.

pblazej · 2026-09-11T07:13:15Z

+    /**
+     * Republish all tracks after a full reconnect so the SFU recognizes existing publications.
+     */
+    fun republishTracks() {


This and resendSubscriptionUpdates() run from coroutineScope.launch (RTCEngine.kt:727), which is SupervisorJob() + ioDispatcher with no CoroutineExceptionHandler — so anything thrown here hits the thread's uncaught handler instead of failing the reconnect. Does uniffi throw on use-after-destroy if a concurrent disconnect() closes the manager mid-call?

pblazej

LGTM, added 2 non-blockers above

davidliu added 18 commits July 29, 2026 23:31

LocalDataTrackManager impl

9ea3e26

Move to OutgoingDataTrackManager

64a5d4a

more migration

fea2afe

Remote data track manager

76a5964

sdk wrappers

713a792

update uniffi to use mavencentral artifact

9c9a673

publishDataTrack api

251d7c1

Use Results instead of throwing exceptions

587de90

clean up LocalDataTrack to more similarly match swift api

4815193

data track schema

ed3dc29

Factories to inject the actual and mock data track manager factories

a8c99d9

wire up remote participant data tracks

9b103b4

wiring for UNPUBLISH_DATA_TRACK_RESPONSE

424bb14

quick reconnect handling

e8c8f34

wait until publisher open

b26ca2d

DataTrackFrameSender

aff6491

hook up e2ee

c0f1fa8

fix data tracks not properly flowing after reconnect

380b1d7

davidliu requested review from MaxHeimbrock and xianshijing-lk as code owners August 20, 2026 16:37

davidliu marked this pull request as draft August 20, 2026 16:39

devin-ai-integration Bot reviewed Aug 20, 2026

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davidliu marked this pull request as ready for review August 26, 2026 18:40

davidliu requested review from ladvoc and pblazej August 26, 2026 18:40

cleanup

3274297

davidliu added 2 commits September 1, 2026 19:14

add attributes to TokenSource due to test failure

602d79e

extract data channel logic and simplification

d40a61f

handle potential exceptions when loading uniffi

317beaa

remove debug logs

88029f7

davidliu added 11 commits September 8, 2026 00:06

detekt fixes

61e6e95

missing commit

9e3c3e1

Add DataTrackFrameFormat to enforce requiring a frameEncoding for a s…

86d3ae3

…chema

make DataTrackPublished and Unpublished events symmetric

105b8b6

LocalDataTrack doc fix

26bd6a9

fix up DataTrackStream not properly sharing frames across collectors

d02cf8f

signalclient: guard against sendEncodedRequest with garbage data

d2f13a6

remove unneeded copy of packets to be sent

9f12dcb

remove redundant write to hasPublished

476b3af

attributes for tokensource (for the protocol upgrade)

1ab1bdc

clean up orphaned code

8714e2a

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davidliu added 3 commits September 8, 2026 03:54

toml file cleanup

8142908

remove redundant uses-sdk

35d0d5d

document passing in bad track frame format is an error

4276935

ladvoc reviewed Sep 10, 2026

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xianshijing-lk reviewed Sep 11, 2026

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pblazej reviewed Sep 11, 2026

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pblazej approved these changes Sep 11, 2026

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