/**
* Throttler for WebSocket broadcasts to prevent overwhelming clients
* Ensures clients receive rate-limited updates while FMDM stays current
*/
export interface ThrottlerConfig {
maxUpdatesPerSecond: number;
debounceMs: number;
}
export class BroadcastThrottler {
private lastBroadcastTime: number = 0;
private pendingBroadcast: (() => void) | null = null;
private throttleTimer: NodeJS.Timeout | null = null;
private debounceTimer: NodeJS.Timeout | null = null;
// Calculate interval from rate
private readonly updateInterval: number;
constructor(private config: ThrottlerConfig) {
this.updateInterval = 1000 / config.maxUpdatesPerSecond;
}
/**
* Request a broadcast (may be throttled)
*/
requestBroadcast(broadcastFn: () => void): void {
const now = Date.now();
const timeSinceLastBroadcast = now - this.lastBroadcastTime;
// Clear existing debounce timer - we have a new update
if (this.debounceTimer) {
clearTimeout(this.debounceTimer);
this.debounceTimer = null;
}
// Can we broadcast immediately?
if (timeSinceLastBroadcast >= this.updateInterval) {
// Clear any pending throttle timer
if (this.throttleTimer) {
clearTimeout(this.throttleTimer);
this.throttleTimer = null;
this.pendingBroadcast = null;
}
// Broadcast immediately
this.performBroadcast(broadcastFn);
} else {
// Store the latest broadcast function
this.pendingBroadcast = broadcastFn;
// Schedule for next allowed time if not already scheduled
if (!this.throttleTimer) {
const delay = this.updateInterval - timeSinceLastBroadcast;
this.throttleTimer = setTimeout(() => {
this.throttleTimer = null;
if (this.pendingBroadcast) {
this.performBroadcast(this.pendingBroadcast);
this.pendingBroadcast = null;
}
}, delay);
}
}
// Always set a debounce timer to ensure final state is broadcast
this.debounceTimer = setTimeout(() => {
this.debounceTimer = null;
// Clear throttle timer if still pending
if (this.throttleTimer) {
clearTimeout(this.throttleTimer);
this.throttleTimer = null;
}
// Broadcast the final state
if (this.pendingBroadcast) {
this.performBroadcast(this.pendingBroadcast);
this.pendingBroadcast = null;
} else {
// Even if no pending broadcast, ensure we send current state
this.performBroadcast(broadcastFn);
}
}, this.config.debounceMs);
}
/**
* Force an immediate broadcast (bypasses throttling)
*/
forceBroadcast(broadcastFn: () => void): void {
// Cancel any pending timers
if (this.throttleTimer) {
clearTimeout(this.throttleTimer);
this.throttleTimer = null;
}
if (this.debounceTimer) {
clearTimeout(this.debounceTimer);
this.debounceTimer = null;
}
this.pendingBroadcast = null;
this.performBroadcast(broadcastFn);
}
/**
* Clean up timers
*/
dispose(): void {
if (this.throttleTimer) {
clearTimeout(this.throttleTimer);
this.throttleTimer = null;
}
if (this.debounceTimer) {
clearTimeout(this.debounceTimer);
this.debounceTimer = null;
}
this.pendingBroadcast = null;
}
private performBroadcast(broadcastFn: () => void): void {
this.lastBroadcastTime = Date.now();
broadcastFn();
}
}
