From 3fa793bef6de92cdabef87baf2b60c8fabfd8116 Mon Sep 17 00:00:00 2001
From: Vutsal <vutsalsinghal@gmail.com>
Date: Sat, 7 Mar 2026 21:51:28 -0800
Subject: [PATCH] Refactor scheduler to use CronExpressionParser

---
 app/server/core/scheduler.ts | 71 +++++++++++++++++++++++++++++++++++-
 1 file changed, 69 insertions(+), 2 deletions(-)

diff --git a/app/server/core/scheduler.ts b/app/server/core/scheduler.ts
index d115fbeb..5a45b526 100644
--- a/app/server/core/scheduler.ts
+++ b/app/server/core/scheduler.ts
@@ -1,4 +1,4 @@
-import cron, { type ScheduledTask } from "node-cron";
+import CronExpressionParser from "cron-parser";
 import { logger } from "../utils/logger";
 
 export abstract class Job {
@@ -7,6 +7,73 @@ export abstract class Job {
 
 type JobConstructor = new () => Job;
 
+class ScheduledTask {
+	private timer: ReturnType<typeof setTimeout> | null = null;
+	private active = true;
+	private running = false;
+
+	constructor(
+		private readonly jobName: string,
+		private readonly cronExpression: string,
+		private readonly run: () => Promise<void>,
+	) {
+		this.scheduleNext();
+	}
+
+	private getDelay(fromDate: Date) {
+		try {
+			const interval = CronExpressionParser.parse(this.cronExpression, {
+				currentDate: fromDate,
+				tz: Intl.DateTimeFormat().resolvedOptions().timeZone,
+			});
+			const nextRun = interval.next().toDate();
+			return Math.max(0, nextRun.getTime() - Date.now());
+		} catch (error) {
+			logger.error(`Failed to parse cron expression for ${this.jobName}:`, error);
+			return 60_000;
+		}
+	}
+
+	private scheduleNext(fromDate = new Date()) {
+		if (!this.active) return;
+
+		const delay = this.getDelay(fromDate);
+		this.timer = setTimeout(() => {
+			void this.tick();
+		}, delay);
+	}
+
+	private async tick() {
+		if (!this.active) return;
+
+		if (this.running) {
+			logger.warn(`Skipping overlapping run for job ${this.jobName}`);
+			this.scheduleNext(new Date());
+			return;
+		}
+
+		this.running = true;
+		try {
+			await this.run();
+		} finally {
+			this.running = false;
+			this.scheduleNext(new Date());
+		}
+	}
+
+	async stop() {
+		this.active = false;
+		if (this.timer) {
+			clearTimeout(this.timer);
+			this.timer = null;
+		}
+	}
+
+	async destroy() {
+		await this.stop();
+	}
+}
+
 class SchedulerClass {
 	private tasks: ScheduledTask[] = [];
 
@@ -18,7 +85,7 @@ class SchedulerClass {
 		const job = new JobClass();
 		return {
 			schedule: (cronExpression: string) => {
-				const task = cron.schedule(cronExpression, async () => {
+				const task = new ScheduledTask(JobClass.name, cronExpression, async () => {
 					try {
 						await job.run();
 					} catch (error) {