chore: add heartbeat

packages/extension/src/background.ts

@@ -77,6 +77,26 @@ chrome.tabs.onRemoved.addListener(() => {
   getActiveTabs();
 });
 
+// add heartbeat using alarms to prevent the service worker from being killed as
+// much as possible.
+chrome.alarms.onAlarm.addListener(async () => {
+  await chrome.storage.local.set({ 'last-heartbeat': new Date().getTime() });
+})
+
+chrome.runtime.onInstalled.addListener(({ reason }) => {
+  if (
+    reason !== chrome.runtime.OnInstalledReason.INSTALL &&
+    reason !== chrome.runtime.OnInstalledReason.UPDATE
+  )
+    return
+
+  chrome.alarms.create("heartbeat", {
+    periodInMinutes: 0.5,
+  })
+})
+
+startHeartbeat()
+
 // initial setup
 cryptoWaitReady()
   .then((): void => {

packages/extension/src/heartbeat.ts

@@ -0,0 +1,39 @@
+// Copyright 2019-2024 @polkadot/extension authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Heartbeat functions as described by google.
+ *
+ * @see https://developer.chrome.com/docs/extensions/develop/migrate/to-service-workers#keep_a_service_worker_alive_continuously
+ */
+
+let heartbeatInterval: string | number | NodeJS.Timeout | undefined;
+
+async function runHeartbeat() {
+  await chrome.storage.local.set({ 'last-heartbeat': new Date().getTime() });
+}
+
+/**
+ * Starts the heartbeat interval which keeps the service worker alive. Call
+ * this sparingly when you are doing work which requires persistence, and call
+ * stopHeartbeat once that work is complete.
+ */
+async function startHeartbeat() {
+  // Run the heartbeat once at service worker startup.
+  runHeartbeat().then(() => {
+    // Then again every 20 seconds.
+    heartbeatInterval = setInterval(runHeartbeat, 20 * 1000);
+  });
+}
+
+async function stopHeartbeat() {
+  clearInterval(heartbeatInterval);
+}
+
+/**
+ * Returns the last heartbeat stored in extension storage, or undefined if
+ * the heartbeat has never run before.
+ */
+async function getLastHeartbeat() {
+  return (await chrome.storage.local.get('last-heartbeat'))['last-heartbeat'];
+}