feat(browser): Flush offline queue on flush and browser online event (#14764)

This PR:
- Resets the offline queue time on `flush` so that sending is retried
- In the browser calls `flush` when the `online` event is fired

Author: timfish

packages/browser/src/transports/offline.ts

@@ -1,5 +1,6 @@
 import type { BaseTransportOptions, Envelope, OfflineStore, OfflineTransportOptions, Transport } from '@sentry/core';
 import { makeOfflineTransport, parseEnvelope, serializeEnvelope } from '@sentry/core';
+import { WINDOW } from '../helpers';
 import { makeFetchTransport } from './fetch';
 
 // 'Store', 'promisifyRequest' and 'createStore' were originally copied from the 'idb-keyval' package before being
@@ -158,7 +159,15 @@ function createIndexedDbStore(options: BrowserOfflineTransportOptions): OfflineS
 function makeIndexedDbOfflineTransport<T>(
   createTransport: (options: T) => Transport,
 ): (options: T & BrowserOfflineTransportOptions) => Transport {
-  return options => createTransport({ ...options, createStore: createIndexedDbStore });
+  return options => {
+    const transport = createTransport({ ...options, createStore: createIndexedDbStore });
+
+    WINDOW.addEventListener('online', async _ => {
+      await transport.flush();
+    });
+
+    return transport;
+  };
 }
 
 /**

packages/browser/test/transports/offline.test.ts

@@ -64,6 +64,7 @@ describe('makeOfflineTransport', () => {
     await deleteDatabase('sentry');
     (global as any).TextEncoder = TextEncoder;
     (global as any).TextDecoder = TextDecoder;
+    (global as any).addEventListener = () => {};
   });
 
   it('indexedDb wrappers push, unshift and pop', async () => {
@@ -115,4 +116,32 @@ describe('makeOfflineTransport', () => {
     expect(queuedCount).toEqual(1);
     expect(getSendCount()).toEqual(2);
   });
+
+  it('flush forces retry', async () => {
+    const { getSendCount, baseTransport } = createTestTransport(new Error(), { statusCode: 200 }, { statusCode: 200 });
+    let queuedCount = 0;
+    const transport = makeBrowserOfflineTransport(baseTransport)({
+      ...transportOptions,
+      shouldStore: () => {
+        queuedCount += 1;
+        return true;
+      },
+      url: 'http://localhost',
+    });
+    const result = await transport.send(ERROR_ENVELOPE);
+
+    expect(result).toEqual({});
+
+    await delay(MIN_DELAY * 2);
+
+    expect(getSendCount()).toEqual(0);
+    expect(queuedCount).toEqual(1);
+
+    await transport.flush();
+
+    await delay(MIN_DELAY * 2);
+
+    expect(queuedCount).toEqual(1);
+    expect(getSendCount()).toEqual(1);
+  });
 });

packages/core/src/transports/offline.ts

@@ -170,7 +170,15 @@ export function makeOfflineTransport<TO>(
 
     return {
       send,
-      flush: t => transport.flush(t),
+      flush: timeout => {
+        // If there's no timeout, we should attempt to flush the offline queue.
+        if (timeout === undefined) {
+          retryDelay = START_DELAY;
+          flushIn(MIN_DELAY);
+        }
+
+        return transport.flush(timeout);
+      },
     };
   };
 }