Feature suggestion: pause sync when offline

[obedm503]

I've been playing with the new SyncManager and I have to say I am enjoying it as it puts Signaldb almost on par with other similar libraries.

In that time I noticed some possible areas of improvement. The main ones are network awareness and improvements around remote changes.

It would be nice if the SyncManager automatically paused sending push requests when the device went offline and resumed via the online and offline window events. This is technically already possible but it's cumbersome as it involves throwing and catching errors inside the push & pull methods so the sync manager knows the sync failed and retries later.

If you think this is out of scope, the sync manager could expose the pause and pauseAll methods (opposite of sync and syncAll) and let the library user implement event listening and cleanup.

Related to this is that it would be nice if the syncManager's registerRemoteChange changed how it executes. I believe it should be called for each collection as part of sync instead of once in the constructor. This way, it could also receive the collectionOptions (just like push and pull) allowing each collection to connect to an entirely different source or use different configuration options.

Also, the registerRemoteChange method should allow returning a cleanup function so we can gracefully shut down the remote data source and avoid memory leaks and other issues.

If registerRemoteChange gets called for each collection on sync and its cleanup function on pause, then going offline and back online would be significantly simpler. It would be a matter of just calling pauseAll and syncAll on the offline and online events respectively.

Thanks for creating SignalDB @maxnowack

[maxnowack]

I currently handle the offline state exactly like you do in trellix-offline (Throwing an error if the device is offline).
I don't think that handling offline/online state in SignalDB is really possible as this check depends a lot on the specific environment. In the browser we have navigator.onLine but in native frameworks (React Native, CapacitorJS, etc.) there are different ways how to check the connection state.

I'm not sure yet about changing the behavior of registerRemoteChange execution, however I really like the idea of the pause/pauseAll functionality.
Do you want to hack on it yourself and create a PR or should I implement this? 🙂

[obedm503]

Made a draft PR #951. Let me know what you think.