Saved messages not appearing in second device

[adbenitez]

I am afraid that some messages are getting miss since 2.43.0 (desktop core is 2.43.0 but android is 2.44.0), I noticed this first in #7952 where I focused on the channel problem but as I said there, there were another account without channel where normal messages were not appearing in both devices

now it happened in the same account where I have the channel:

I saved some messages (some are videos but other are simple text messages) in android and they are nowhere to be found in desktop:

in Desktop nothing of this appears, even if the messages themselves are in the original chat, so it was the sync-messages that got lost somehow maybe while syncing after being offline the sync messages got somehow processed before the actual messages. If I now try to save some of that messages again while both devices are online, it works, here you can see desktop's saved messages after I saved a message again just now:

[Hocuri]

This may have been triggered in this way:

• The message was sent to a rather-slow relay
• Only one of your device was online, and on this device you marked the message as bookmarked
• The bookmark-sync-message was sent on a faster relay
• You turned on your Desktop device, and it received the bookmark-sync-message first, and ignored it

So, the actionable item here is to make sure that bookmark-sync-messages work fine even if the sync message arrives before the original message.

[iequidoo]

As we send messages to all own relays, i think that the fix is to not create a tombstone for a sync message if the referenced messages couldn't be found. Then, when everything is received from the "rather-slow" relay, it will eventually work. The same problem we have for MDNs (#8030 (comment)) and, obviously, for edit and deletion requests and reactions. All these messages are lightweight, so downloading them once more because there's no tombstone looks fine.

... For deletion requests i've implemented a more robust approach: #8158

[iequidoo]

Sync messages consist of multiple sync items, so currently there are two ways of things going wrong:

1. A sync item isn't applied at all because it failed to apply before and the whole sync message is tombstoned.
2. A sync item is applied twice because the tombstone has been already pruned.

We can't protect from "1." because the whole message may be lost (not delivered), but we can at least protect from "2." if instead of tombstoning all sync messages we'll remember which sync items are already applied, say, in a separate table. We should clean up old items in this table so that it doesn't grow infinitely, but then if a sync message arrived is outside of the "applying window", it shall be just dropped.

For now i'm going to fix the bug for ChatEdit, IrohNodeAddr and reaction messages by just not tombstoning failed-to-apply messages. Particularly, the problem with reactions reproduces quite often for me.

... The problem exists also for MDNs.