fix: Http clients getting stuck on 401 (#1034)

Author: Chriztiaan

.changeset/witty-students-cross.md

@@ -0,0 +1,5 @@
+---
+'@powersync/shared-internals': patch
+---
+
+Fixed an issue where clients using the HTTP connection method could get stuck in an endless auth-error retry loop when their token expired while disconnected (e.g. after network interruptions or device sleep).

packages/node/tests/sync.test.ts

@@ -92,6 +92,43 @@ describe('Sync', () => {
     ]);
   });
 
+  mockSyncServiceTest('refetches credentials when HTTP stream returns 401', async ({ syncService }) => {
+    // The /sync/stream 401 should invalidate the cached credentials so the retry fetches a fresh token.
+    let fetchCredentialsCount = 0;
+    const connector = new TestConnector();
+    connector.fetchCredentials = async () => {
+      fetchCredentialsCount++;
+      return {
+        endpoint: 'https://powersync.example.org',
+        token: `token-${fetchCredentialsCount}`
+      };
+    };
+
+    syncService.installRequestInterceptor(async (request) => {
+      if (request.url.endsWith('/sync/stream') && request.headers.get('Authorization') === 'Token token-1') {
+        return new Response(
+          JSON.stringify({ error: { code: 'PSYNC_S2103', description: 'Authentication required' } }),
+          {
+            status: 401,
+            headers: { 'content-type': 'application/json' }
+          }
+        );
+      }
+      return undefined;
+    });
+
+    const database = await syncService.createDatabase();
+    database.connect(connector, {
+      connectionMethod: SyncStreamConnectionMethod.HTTP,
+      retryDelayMs: 100
+    });
+
+    // The first attempt uses token-1 and gets a 401. The SDK must invalidate the cached
+    // credentials and retry with a freshly fetched token-2, which connects successfully.
+    await vi.waitFor(() => expect(fetchCredentialsCount).toBeGreaterThanOrEqual(2), { timeout: 2000 });
+    await vi.waitFor(() => expect(syncService.connectedListeners).toHaveLength(1), { timeout: 2000 });
+  });
+
   mockSyncServiceTest('reconnects immediately after changed connection', async ({ syncService }) => {
     let database = await syncService.createDatabase();
     database.connect(new TestConnector(), {

packages/node/tests/utils.ts

@@ -110,11 +110,14 @@ export function createMockSyncServiceTest(bson: boolean) {
       const databaseName = `test-${crypto.randomUUID()}.db`;
 
       const listeners: Listener[] = [];
-      let requestInterceptor: (request: Request) => Promise<void> = async () => {};
+      let requestInterceptor: (request: Request) => Promise<Response | void> = async () => {};
 
       const inMemoryFetch: typeof fetch = async (info, init?) => {
         const request = new Request(info, init);
-        await requestInterceptor(request);
+        const intercepted = await requestInterceptor(request);
+        if (intercepted) {
+          return intercepted;
+        }
 
         if (request.url.endsWith('/sync/stream')) {
           const body = await request.json();
@@ -201,7 +204,7 @@ export function createMockSyncServiceTest(bson: boolean) {
 export const mockSyncServiceTest = createMockSyncServiceTest(false);
 
 export interface MockSyncService {
-  installRequestInterceptor(interceptor: (request: Request) => Promise<void>): void;
+  installRequestInterceptor(interceptor: (request: Request) => Promise<Response | void>): void;
   pushLine: (line: StreamingSyncLine) => void;
   connectedListeners: any[];
 

packages/shared-internals/src/client/sync/stream/AbstractRemote.ts

@@ -315,6 +315,11 @@ export abstract class AbstractRemote {
           message: `Could not POST streaming to ${path} - ${res.status} - ${res.statusText}: ${text}`,
           error
         });
+
+        if (res.status === 401) {
+          this.invalidateCredentials();
+        }
+
         throw error;
       }