throttle presence updates over http

.changeset/light-plants-occur.md

@@ -0,0 +1,6 @@
+---
+'@verdant-web/common': patch
+'@verdant-web/store': patch
+---
+
+Throttle presence updates over http sync to reduce http requests

packages/common/src/utils.ts

@@ -153,3 +153,29 @@ export function debounce<T extends (...args: any[]) => any>(
 		timeout = setTimeout(() => fn.apply(context, args), wait);
 	} as any;
 }
+
+export function throttle<T extends (...args: any[]) => any>(
+	fn: T,
+	wait: number,
+): T {
+	let lastTime = 0;
+
+	// invoke once for the last call
+	let trailingTimeout: any;
+
+	return function (this: any, ...args: any[]) {
+		const context = this;
+		const now = Date.now();
+		if (now - lastTime >= wait) {
+			lastTime = now;
+			fn.apply(context, args);
+			clearTimeout(trailingTimeout);
+		} else {
+			clearTimeout(trailingTimeout);
+			trailingTimeout = setTimeout(() => {
+				lastTime = now;
+				fn.apply(context, args);
+			}, wait);
+		}
+	} as any;
+}

packages/store/src/sync/PushPullSync.ts

@@ -1,9 +1,12 @@
 import {
 	ClientMessage,
 	EventSubscriber,
+	PresenceUpdateMessage,
 	ServerMessage,
 	VerdantErrorCode,
+	debounce,
 	isVerdantErrorResponse,
+	throttle,
 } from '@verdant-web/common';
 import { Metadata } from '../metadata/Metadata.js';
 import { PresenceManager } from './PresenceManager.js';
@@ -144,10 +147,17 @@ export class PushPullSync
 		this.emit('message', message);
 	};
 
+	// reduce rate of presence messages sent; each one would trigger an HTTP
+	// request, which is not ideal if presence is updating rapidly.
+	throttledPresenceUpdate = throttle((message: PresenceUpdateMessage) => {
+		this.sendRequest([message]);
+	}, 3000);
+
 	send = (message: ClientMessage) => {
 		// only certain messages are sent for pull-based sync.
 		switch (message.type) {
 			case 'presence-update':
+				return this.throttledPresenceUpdate(message);
 			case 'sync':
 			case 'heartbeat':
 				return this.sendRequest([message]);