feat: make retransmit timer use setTimeout instead of setInterval #96

This is so that it only runs when packets are inflight, and lowers idle cpu usage

Author: Julusian

src/lib/atemSocketChild.ts

@@ -52,7 +52,7 @@ export class AtemSocketChild {
 
 	private _connectionState = ConnectionState.Closed
 	private _reconnectTimer: NodeJS.Timer | undefined
-	private _retransmitTimer: NodeJS.Timer | undefined
+	private _retransmitTimer: NodeJS.Timeout | undefined
 
 	private _nextSendPacketId = 1
 	private _sessionId = 0
@@ -104,14 +104,6 @@ export class AtemSocketChild {
 				})
 			}, CONNECTION_RETRY_INTERVAL)
 		}
-		// Check for retransmits every 10 milliseconds
-		if (!this._retransmitTimer) {
-			this._retransmitTimer = setInterval(() => {
-				this._checkForRetransmit().catch((e) => {
-					this.log(`Failed to retransmit: ${e?.message ?? e}`)
-				})
-			}, RETRANSMIT_INTERVAL)
-		}
 	}
 
 	public async connect(address: string, port: number): Promise<void> {
@@ -132,7 +124,7 @@ export class AtemSocketChild {
 
 	private _clearTimers() {
 		if (this._retransmitTimer) {
-			clearInterval(this._retransmitTimer)
+			clearTimeout(this._retransmitTimer)
 			this._retransmitTimer = undefined
 		}
 		if (this._reconnectTimer) {
@@ -198,6 +190,7 @@ export class AtemSocketChild {
 			payload: buffer,
 			resent: 0,
 		})
+		this._triggerRetransmitTimer()
 	}
 
 	private _recreateSocket(): Socket {
@@ -306,6 +299,8 @@ export class AtemSocketChild {
 						return true
 					}
 				})
+
+				this._triggerRetransmitTimer()
 				ps.push(this.onPacketsAcknowledged(ackedCommands))
 				// this.log(`${Date.now()} Got ack ${ackPacketId} Remaining=${this._inFlight.length}`)
 			}
@@ -379,8 +374,28 @@ export class AtemSocketChild {
 		}
 	}
 
+	private _triggerRetransmitTimer(): void {
+		if (!this._inFlight.length && this._retransmitTimer) {
+			clearTimeout(this._retransmitTimer)
+			delete this._retransmitTimer
+			return
+		}
+
+		if (!this._retransmitTimer) {
+			this._retransmitTimer = setTimeout(() => {
+				delete this._retransmitTimer
+				this._checkForRetransmit().catch((e) => {
+					this.log(`Failed to retransmit: ${e?.message ?? e}`)
+				})
+			}, RETRANSMIT_INTERVAL)
+		}
+	}
+
 	private async _checkForRetransmit(): Promise<void> {
 		if (!this._inFlight.length) return
+
+		this._triggerRetransmitTimer()
+
 		const now = performance.now()
 		for (const sentPacket of this._inFlight) {
 			if (sentPacket.lastSent + IN_FLIGHT_TIMEOUT < now) {