John Todd wrote:
I, for one, would be very interested to see anyone's results with the logically extreme version of "keeping state", meaning keeping media state.
Asterisk can't perform failover between two discreet systems and maintain media state, if media is indeed being handled as a B2BUA and RTP relay. We (Digium) have been asked a few times about it, but the engineering effort is much much larger than the payoff and nobody from the open-source community has stepped forward with any code. The amount of synchronization data that would have to be exchanged between two systems running RTP and signaling is large. VERY large. That's not to say it can't be done, but I just haven't seen it done even with VMWare or other VM-based systems which may claim to be able to synchronize instances between chassis platforms.
Most failures aren't hardware or chassis-based; they're software-based, so duplicating corrupted memory structures between two machines will give you (surprise!) two dead machines, or two dead apps on two machines regardless of the application being used. So this has limited use. Anyone who has code that relays minimal state WITHOUT mirroring the whole app/system so that two instances of (for instance) Asterisk could be synchronized without shared fate... I'll be very VERY interested in that. :-)
So: has anyone out there done this with any RTP-capable systems running on Linux (Asterisk or otherwise)? If so, can you post notes and operational techniques?
I believe this effort is a specious and misguided waste of time, and the interest in it is principally the expression of the following deficiencies in the thought process of those doing the asking: (1) Exaggerated, megalomaniacal perceptions of the relative importance of four-9s vs. nine-9s uptime, and with it, lack of cursory accompanying understanding of the Pareto principle; (2) Lack of non-superficial comprehension of how the technology works, which you have covered quite well with your post. These are not satellite guidance systems. That level of failover is simply unnecessary, although I have met more than one proud ITSP owner who is prepared to solicit proposals for magic. -- Alex Balashov - Principal Evariste Systems Web : http://www.evaristesys.com/ Tel : (+1) (678) 954-0670 Direct : (+1) (678) 954-0671