[Opensim-users] r7930 breaks comms with older versions

[Justin Clark-Casey]

Diva Canto wrote:
> Justin Clark-Casey wrote:
>> tl;dr.  So maybe the single monolithic current interface version number should be split into 3
>>
>> Grid comms interface version
>> Region neighbour comms interface version
>> Region teleport comms interface version
>>   
> The neighbors and teleports can be made the same, because they use the 
> exact same set of interregion comms. And I think that the right thing to 
> do is to add the protocol version number in the messages themselves, 
> just like lots of other protocols do. I should have thought about this 
> before. I'll add it next week.

I guess I was thinking of some future situation where neighbour and teleport comms could vary.  Though right now the 
pragmatic thing could well be just to combine the two.

You have a point about embedding version numbers in all messages, but is this precisely the same kind of situation? 
Unlike HTTP (one protocol which always sends a version number, I believe), we don't have a single interaction but a 
continuous series of interactions between two regions.  The code could check the version number on each message but 
would could also just do it when the neighbour initially appears.

Even so, I imagine this would still probably be a good thing to do.  One could do the same thing with grid comms, though 
maybe not with viewer comms since small message size is much more crucial there (?)

> 
> So if a region comes up and tries to engage with a neighbor that's 
> running an older/incompatible version of the interregion protocol, that 
> neighbor should essentially be made invisible, and vice-versa. And if 
> you try to TP to a region running older/incompatible interregion comms, 
> the TP will fail with a meaningful message, but nobody will crash.
> 
> What do you think?

I think the invisibility thing is an interesting idea.  Do you think that this would make things more confusing for 
people? (the map says there's a region here but I can't see it!).

-- 
justincc
Justin Clark-Casey
http://justincc.wordpress.com