Jitter updater poll timeout

ts/updater/common.ts

@@ -25,6 +25,7 @@ import { DialogType } from '../types/Dialogs';
 import * as Errors from '../types/errors';
 import { isAlpha, isBeta, isStaging } from '../util/version';
 import { strictAssert } from '../util/assert';
+import { drop } from '../util/drop';
 
 import * as packageJson from '../../package.json';
 import {
@@ -46,7 +47,7 @@ import {
   isValidPreparedData as isValidDifferentialData,
 } from './differential';
 
-const INTERVAL = 30 * durations.MINUTE;
+const POLL_INTERVAL = 30 * durations.MINUTE;
 
 type JSONVendorSchema = {
   minOSVersion?: string;
@@ -148,13 +149,7 @@ export abstract class Updater {
   public async start(): Promise<void> {
     this.logger.info('updater/start: starting checks...');
 
-    setInterval(async () => {
+    this.schedulePoll();
-      try {
-        await this.checkForUpdatesMaybeInstall();
-      } catch (error) {
-        this.logger.error(`updater/start: ${Errors.toLogFormat(error)}`);
-      }
-    }, INTERVAL);
 
     await this.deletePreviousInstallers();
     await this.checkForUpdatesMaybeInstall();
@@ -216,6 +211,33 @@ export abstract class Updater {
   // Private methods
   //
 
+  private schedulePoll(): void {
+    const now = Date.now();
+
+    const earliestPollTime = now - (now % POLL_INTERVAL) + POLL_INTERVAL;
+    const selectedPollTime = Math.round(
+      earliestPollTime + Math.random() * POLL_INTERVAL
+    );
+    const timeoutMs = selectedPollTime - now;
+
+    this.logger.info(`updater/start: polling in ${timeoutMs}ms`);
+
+    setTimeout(() => {
+      drop(this.safePoll());
+    }, timeoutMs);
+  }
+
+  private async safePoll(): Promise<void> {
+    try {
+      this.logger.info('updater/start: polling now');
+      await this.checkForUpdatesMaybeInstall();
+    } catch (error) {
+      this.logger.error(`updater/start: ${Errors.toLogFormat(error)}`);
+    } finally {
+      this.schedulePoll();
+    }
+  }
+
   private async downloadAndInstall(
     updateInfo: UpdateInformationType,
     mode: DownloadMode