I’d just like to mention that long discussions about specific issues is probably better done on their own discourse post or an issue on the appropriate issue tracker.
Right now we’ve got multiple topics of conversation going and we’re potentially interleaving the discussions. I think it’s going to make it harder for people to retroactively follow these discussions.
But please do continue the discussions.
Unfortunately we don’t have that yet. We do have a GUID for the publisher that sent a message when you receive one with a subscription, but not the sequence number which is part of a series of sequence numbers for that particular publisher. It would be added here:
As for how the middleware could supply it, I think RTPS may already have this but it may not be exposed. If not we could potentially send it with some of the available metadata options available in RTPS. Worst case a middleware could wrap all user messages in a message that has an additional sequence number field, which is sort of what we do for Services.