%wojtek - as I remember you added some logic to optimize broadcasting presence to offline users. May this be result of this changes? And what you think about current behavior? Should we change it in default to be same as in RFC6121?

%andrzej.wojcik Yes, there was an optimisation added with #1714 and there are two levels and in general I think this optimisation makes perfect sense (taking PEP aside for a moment) because locally, with the conditions mentioned in the ticket (local users, complete knowledge about the state) it really doesn't make much sense to generate abundance of offline presence / probes if we are certain that those users are offline, which would simply generate offline packets that would be simply dropped moments later.

Addendum - RFC1621 clarified a bit how/when to send probe, but I think that with current handling of presence in Tigase we are still compatible. We cannot skip sending additional probe as handling of in-initial doesn't entail re-broadcasting users presence as response.

Looks like

is required for PEP to work correctly if user is offline.

Yes, Wojciech is correct. This is an old optimization and it is really useful and improved throughput and performance significantly. Usually less than 50% of contacts are online, on some systems, it goes down to 20% of contacts. So skipping unnecessary presences to offline contacts which we are 100% sure they are offline saves us a lot of traffic.

I wonder, if there is a way to improve current mechanism to make it still work in such a way that it skips offline users but it still compatible with PEP. I mean, presences are skipped in smarter way, that some are skipped whereas those for PEP are not.

What do you think? To be honest I do not have time to read the spec in details to tell whether this makes sense or not.

I checked once again and PEP works with default settings only if both users are online - this is bad because we would not get response from offline users PEP nodes but it is also good as in most cases we do not need PEP data from offline users (ie. avatars, moods, etc.) as most XMPP clients by default presents only online users.

So to sum up, I think that current behavior is acceptable in most cases and in other we can always disable presence optimization if needed, as I am not able to find any way to make PEP work for offline contacts and still be able to use presence optimization.

I suppose we may close this issue, but I would suggest to add information about this behavior to our documentation.

Ok, good, since we have a way to configure Tigase to work in fully compliance mode, than this is OK.