Expose RPC max round trip latency in performRpc

.changes/rpc-max-round-trip-latency

@@ -0,0 +1 @@
+patch type="added" "Allow customizing `maxRoundTripLatency` on `LocalParticipant.performRpc` for high-latency networks

Sources/LiveKit/Core/RpcClientManager.swift

@@ -22,6 +22,14 @@ import Foundation
 /// publishing of v1 RPC packets / v2 RPC request streams. `LocalParticipant.performRpc`
 /// is a one-line proxy that forwards into this actor.
 actor RpcClientManager: Loggable {
+    /// Default upper bound on round-trip latency to the destination, in seconds. Used by the
+    /// ack watchdog and to clamp the effective response timeout. Exposed so the public
+    /// `LocalParticipant.performRpc` overloads can share the same default.
+    static let defaultMaxRoundTripLatency: TimeInterval = 7
+
+    /// Default timeout for receiving a response after the initial connection, in seconds.
+    static let defaultResponseTimeout: TimeInterval = 15
+
     private weak var room: Room?
 
     private var pendingAcks: Set<String> = Set()
@@ -50,15 +58,15 @@ actor RpcClientManager: Loggable {
     func performRpc(destinationIdentity: Participant.Identity,
                     method: String,
                     payload: String,
-                    responseTimeout: TimeInterval = 15) async throws -> String
+                    responseTimeout: TimeInterval = RpcClientManager.defaultResponseTimeout,
+                    maxRoundTripLatency: TimeInterval = RpcClientManager.defaultMaxRoundTripLatency) async throws -> String
     {
         let room = try requireRoom()
 
         let remoteClientProtocol = room.remoteParticipants[destinationIdentity]?.clientProtocol ?? .v0
         let useStreamTransport = remoteClientProtocol >= .v1 && Self.serverSupportsRpcV2(room.serverVersion)
 
         let requestId = UUID().uuidString
-        let maxRoundTripLatency: TimeInterval = 7
         let minEffectiveTimeout: TimeInterval = maxRoundTripLatency + 1
         let effectiveTimeout = max(responseTimeout, minEffectiveTimeout)
 

Sources/LiveKit/Participant/LocalParticipant+RPC.swift

@@ -26,27 +26,33 @@ public extension LocalParticipant {
     ///   15 KB payload size limit (otherwise rejected with `REQUEST_PAYLOAD_TOO_LARGE`).
     ///
     /// ObjC: auto-generated as
-    /// `performRpcWithDestinationIdentity:method:payload:responseTimeout:completionHandler:`.
+    /// `performRpcWithDestinationIdentity:method:payload:responseTimeout:maxRoundTripLatency:completionHandler:`.
     ///
     /// - Parameters:
     ///   - destinationIdentity: The identity of the destination participant
     ///   - method: The method name to call
     ///   - payload: The payload to pass to the method
     ///   - responseTimeout: Timeout for receiving a response after the initial connection (in seconds).
-    ///     If a value less than 8s is provided, it will be automatically clamped to 8s
-    ///     to ensure sufficient time for round-trip latency buffering.
+    ///     If a value less than `maxRoundTripLatency + 1` is provided, it will be automatically
+    ///     clamped to that floor to ensure sufficient time for round-trip latency buffering.
     ///     Default: 15s.
+    ///   - maxRoundTripLatency: Upper bound on round-trip latency to the destination, in seconds.
+    ///     If no ack arrives within this window the call is rejected with
+    ///     `RpcError.BuiltInError.connectionTimeout`. Increase this on high-latency links where
+    ///     the default is too tight. Default: 7s.
     /// - Returns: The response payload
     /// - Throws: RpcError on failure. Details in RpcError.message
     func performRpc(destinationIdentity: Identity,
                     method: String,
                     payload: String,
-                    responseTimeout: TimeInterval = 15) async throws -> String
+                    responseTimeout: TimeInterval = 15,
+                    maxRoundTripLatency: TimeInterval = 7) async throws -> String
     {
         try await requireRoom().rpcClient.performRpc(destinationIdentity: destinationIdentity,
                                                      method: method,
                                                      payload: payload,
-                                                     responseTimeout: responseTimeout)
+                                                     responseTimeout: responseTimeout,
+                                                     maxRoundTripLatency: maxRoundTripLatency)
     }
 
     @available(*, deprecated, message: "registerRpcMethod(_:handler:) has been moved to room.")

Tests/LiveKitObjCTests/RpcObjCTests.m

@@ -94,6 +94,7 @@ - (void)testRegisterAndCallRpc {
                                                        method:@"greet"
                                                       payload:@"World"
                                               responseTimeout:15.0
+                                          maxRoundTripLatency:7.0
                                             completionHandler:^(NSString *response, NSError *err) {
         XCTAssertNil(err);
         rpcResponse = response;