A way to know if an update has been stored (feedback)

[WofWca]

Checklist

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Is your feature request related to a problem? Please describe.
Apparently not all updates are guaranteed to be stored (is it itself a bug? This needs to be documented at least). For example, if you do an update and close/reload the tab immediately, it won't show up on the next load.

There's no conventional way to know in what state the document has been stored in indexedDB. Has the update that I just made been stored? Is it safe to close the tab now?

Describe the solution you'd like
Expose some getter, or method, or add an event (or all at the same time), that lets you determine if the document is stored in indexedDB in the same state as it is in JS right now.

Also I guess this should apply to other persistence adapters (leveldb).

Describe alternatives you've considered
Perhaps additionally a method that upon calling stores the latest update

Additional context
My case:
I'm developing an app that builds the state from a list of updates (like this one). The list is an external thing that persists between page reloads. For performance, I want to store the state of the Y.Doc in browser storage in order to not rebuild it from the list of updates each time. For this I need to remember the index of the last update in the list that has been cached in indexedDB. But I don't know the index because it's not guaranteed that every update made on the doc with the y-indexeddb adapter attached will be saved.

[dmonad]

Apparently not all updates are guaranteed to be stored (is it itself a bug? This needs to be documented at least). For example, if you do an update and close/reload the tab immediately, it won't show up on the next load.

This is news to me. How can I reproduce this?

All updates should be stored immediately. A callback should not be necessary.

[WofWca]

This is news to me. How can I reproduce this?

Sorry about that, I guess I misunderstood the source code. Apparently this can happen much rarer than I initially thought, but still does.
I think it's when you apply changes to a doc and immediately reload/close the page without waiting for the 'update' event to fire. Might need to double check.

Another thing is to maybe ensure that the changes have been saved to disk.

[raineorshine]

@WofWca Updates are persisted every 1 second:

y-indexeddb/src/y-indexeddb.js

Lines 95 to 98 in 41a5e59

	/**
	* Timeout in ms untill data is merged and persisted in idb.
	*/
	this._storeTimeout = 1000

It would be simple to add an emit('stored') event to the _storeUpdate method.

[dmonad]

All updates are stored immediately. The mentioned timeout is only for trimming the updates.

Persisting can fail if you close the web-app before the last transaction finishes - this should be extremely unlikely. However, I'd be happy to accept a PR that adds an event.

[raineorshine]

Ah, thanks for the correction.

Regardless, IndexedDB can be kind of slow. I find myself closing tabs or switching apps before the data gets persisted pretty frequently. I'm considering a synchronous write to localStorage and then flushing to IndexedDB.