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11 changes: 11 additions & 0 deletions src/libs/Network/SequentialQueue.ts
Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,12 @@ function process(): Promise<void> {
return currentRequestPromise;
}

/**
* @param shouldResetPromise Determines whether the isReadyPromise should be reset.
* A READ request will wait until all the WRITE requests are done, using the isReadyPromise promise.
* Resetting can cause unresolved READ requests to hang if tied to the old promise,
* so some cases (e.g., unpausing) require skipping the reset to maintain proper behavior.
*/
function flush(shouldResetPromise = true) {
// When the queue is paused, return early. This will keep an requests in the queue and they will get flushed again when the queue is unpaused
if (isQueuePaused) {
Expand Down Expand Up @@ -198,6 +204,11 @@ function unpause() {
const numberOfPersistedRequests = PersistedRequests.getAll().length || 0;
Log.info(`[SequentialQueue] Unpausing the queue and flushing ${numberOfPersistedRequests} requests`);
isQueuePaused = false;

// When the queue is paused and then unpaused, we call flush which by defaults recreates the isReadyPromise.
// After all the WRITE requests are done, the isReadyPromise is resolved, but since it's a new instance of promise,
// the pending READ request never received the resolved callback. That's why we don't want to recreate
// the promise when unpausing the queue.
flush(false);
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}

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2 changes: 1 addition & 1 deletion tests/unit/APITest.ts
Original file line number Diff line number Diff line change
Expand Up @@ -581,7 +581,7 @@ describe('APITests', () => {
});
});

test('Read request should not stuck when SequentialQueue is paused an resumed', async () => {
test('Read request should not stuck when SequentialQueue is paused and resumed', async () => {
// Given 2 WRITE requests and 1 READ request where the first write request pauses the SequentialQueue
const xhr = jest.spyOn(HttpUtils, 'xhr').mockResolvedValueOnce({previousUpdateID: 1});
API.write('MockWriteCommandOne' as WriteCommand, {});
Expand Down