Use monitonic clock for scheduling poll iterations in Auto Poll mode for improved precision and resistance to system/user clock adjustments

Author: adams85

src/AutoPollConfigService.ts

@@ -4,7 +4,7 @@ import type { IConfigFetcher } from "./ConfigFetcher";
 import type { IConfigService, RefreshResult } from "./ConfigServiceBase";
 import { ClientCacheState, ConfigServiceBase } from "./ConfigServiceBase";
 import type { ProjectConfig } from "./ProjectConfig";
-import { AbortToken, delay } from "./Utils";
+import { AbortToken, delay, getMonotonicTimeMs } from "./Utils";
 
 export const POLL_EXPIRATION_TOLERANCE_MS = 500;
 
@@ -136,14 +136,14 @@ export class AutoPollConfigService extends ConfigServiceBase<AutoPollOptions> im
     let isFirstIteration = true;
     while (!stopToken.aborted) {
       try {
-        const scheduledNextTimeMs = new Date().getTime() + this.pollIntervalMs;
+        const scheduledNextTimeMs = getMonotonicTimeMs() + this.pollIntervalMs;
         try {
           await this.refreshWorkerLogic(isFirstIteration, initialCacheSyncUp);
         } catch (err) {
           this.options.logger.autoPollConfigServiceErrorDuringPolling(err);
         }
 
-        const realNextTimeMs = scheduledNextTimeMs - new Date().getTime();
+        const realNextTimeMs = scheduledNextTimeMs - getMonotonicTimeMs();
         if (realNextTimeMs > 0) {
           await delay(realNextTimeMs, stopToken);
         }

src/Utils.ts

@@ -46,6 +46,10 @@ export function delay(delayMs: number, abortToken?: AbortToken | null): Promise<
   });
 }
 
+export const getMonotonicTimeMs = typeof performance !== "undefined" && typeof performance.now === "function"
+  ? () => performance.now()
+  : () => new Date().getTime();
+
 export function errorToString(err: any, includeStackTrace = false): string {
   return err instanceof Error
     ? includeStackTrace && err.stack ? err.stack : err.toString()