Peer-to-peer sync

[FliegendeWurst]

At the moment I am using Trilium on three devices: my PC, laptop, and smartphone. Of course I would like to keep my notes synchronized between these, but it is a bit annoying that I have to choose one device as the "main" sync server.

My current solution is to synchronize all devices to the PC, but it would be nice if I could sync my laptop and smartphone independently. (For example, if the PC is undergoing lengthy repairs.)

As far as I can tell the issue is that the client currently only tracks lastSyncedPush / lastSyncedPull against one sync server, and the latter ID only makes sense for one particular sync server.
It would be relatively easy to track multiple sync servers, but there are several problems.
Duplicate entity changes need to be ignored (which they are already), and ideally they would not be pushed around needlessly if the sync client already has them (more difficult).
Probably there would be scenarios where the sync peers end up disagreeing on the current entity state, though I can't come up with an example right now.

[maphew]

Always-on peer-to-peer might be too large a can of worms, but I could see a ranked order with a prompt to fall back to secondary or tertiary server being ok, maybe? Or in options screen a list of "remembered servers/devices" that user could copy-paste or radio button to activate.