1 files changed, 42 insertions, 0 deletions
diff --git a/packages/instant/src/util/heartbeater.ts b/packages/instant/src/util/heartbeater.ts
new file mode 100644
index 000000000..c5a823953
--- /dev/null
+++ b/packages/instant/src/util/heartbeater.ts
@@ -0,0 +1,42 @@
+import * as _ from 'lodash';
+
+type HeartbeatableFunction = () => Promise<void>;
+export class Heartbeater {
+    private _intervalId?: number;
+    private _pendingRequest: boolean;
+    private _performingFunctionAsync: HeartbeatableFunction;
+
+    public constructor(_performingFunctionAsync: HeartbeatableFunction) {
+        this._performingFunctionAsync = _performingFunctionAsync;
+        this._pendingRequest = false;
+    }
+
+    public start(intervalTimeMs: number): void {
+        if (!_.isUndefined(this._intervalId)) {
+            throw new Error('Heartbeat is running, please stop before restarting');
+        }
+        this._trackAndPerformAsync();
+        this._intervalId = window.setInterval(this._trackAndPerformAsync.bind(this), intervalTimeMs);
+    }
+
+    public stop(): void {
+        if (this._intervalId) {
+            window.clearInterval(this._intervalId);
+        }
+        this._intervalId = undefined;
+        this._pendingRequest = false;
+    }
+
+    private async _trackAndPerformAsync(): Promise<void> {
+        if (this._pendingRequest) {
+            return;
+        }
+
+        this._pendingRequest = true;
+        try {
+            await this._performingFunctionAsync();
+        } finally {
+            this._pendingRequest = false;
+        }
+    }
+}