feat: scheduler init jitter

src/lib/features/scheduler/scheduler-service.test.ts

@@ -72,7 +72,7 @@ test('Schedules job immediately', async () => {
 
     const job = jest.fn();
 
-    await schedulerService.schedule(job, 10, 'test-id');
+    await schedulerService.schedule(job, 10, 'test-id', 0);
 
     expect(job).toBeCalledTimes(1);
     schedulerService.stop();
@@ -172,7 +172,7 @@ test('Can handle crash of a async job', async () => {
         await Promise.reject('async reason');
     };
 
-    await schedulerService.schedule(job, 50, 'test-id-10');
+    await schedulerService.schedule(job, 50, 'test-id-10', 0);
     await ms(75);
 
     schedulerService.stop();
@@ -236,3 +236,29 @@ it('should emit scheduler job time event when scheduled function is run', async
     await schedulerService.schedule(mockJob, 50, 'testJobId');
     await eventPromise;
 });
+
+test('Delays initial job execution by jitter duration', async () => {
+    const { schedulerService } = createSchedulerTestService();
+
+    const job = jest.fn();
+    const jitterMs = 10;
+
+    await schedulerService.schedule(job, 10000, 'test-id', jitterMs);
+    expect(job).toBeCalledTimes(0);
+
+    await ms(50);
+    expect(job).toBeCalledTimes(1);
+    schedulerService.stop();
+});
+
+test('Does not apply jitter if schedule interval is smaller than max jitter', async () => {
+    const { schedulerService } = createSchedulerTestService();
+
+    const job = jest.fn();
+
+    // default jitter 2s-30s
+    await schedulerService.schedule(job, 1000, 'test-id');
+    expect(job).toBeCalledTimes(1);
+
+    schedulerService.stop();
+});

src/lib/features/scheduler/scheduler-service.ts

@@ -3,6 +3,19 @@ import { Logger, LogProvider } from '../../logger';
 import { IMaintenanceStatus } from '../maintenance/maintenance-service';
 import { SCHEDULER_JOB_TIME } from '../../metric-events';
 
+// returns between min and max seconds in ms
+// when schedule interval is smaller than max jitter then no jitter
+function randomJitter(
+    minMs: number,
+    maxMs: number,
+    scheduleIntervalMs: number,
+): number {
+    if (scheduleIntervalMs < maxMs) {
+        return 0;
+    }
+    return Math.random() * (maxMs - minMs) + minMs;
+}
+
 export class SchedulerService {
     private intervalIds: NodeJS.Timeout[] = [];
 
@@ -26,6 +39,7 @@ export class SchedulerService {
         scheduledFunction: () => void,
         timeMs: number,
         id: string,
+        jitter = randomJitter(2 * 1000, 30 * 1000, timeMs),
     ): Promise<void> {
         const runScheduledFunctionWithEvent = async () => {
             const startTime = process.hrtime();
@@ -61,8 +75,15 @@ export class SchedulerService {
         try {
             const maintenanceMode =
                 await this.maintenanceStatus.isMaintenanceMode();
+
             if (!maintenanceMode) {
-                await runScheduledFunctionWithEvent();
+                if (jitter) {
+                    setTimeout(() => {
+                        runScheduledFunctionWithEvent();
+                    }, jitter);
+                } else {
+                    await runScheduledFunctionWithEvent();
+                }
             }
         } catch (e) {
             this.logger.error(`initial scheduled job failed | id: ${id}`, e);