I did some, I got some anecdotes from people running them. It certainly is possible to handle *some* failure cases, but there are some *other* cases that will be not handled correctly. Personally I've observed OpenSIPS that run out of some internal memory and anyhow you wanted to monitor it it will reply it is alive. It will even route your simple call scenarios well! Unfortunately the "real" calls were *usually* timing out, but always. Sorry, but I can't imagine how you can automatically handle that, i.e. discover that this node is "bad" and fail-over to some other. Even if you do that correctly your monitoring tool can check that this node is operating perfectly well (because after all the traffic is diverted from the faulty node it begins to work well) and will want to move the traffic back. By "impossible" I mean handling all such gray areas. Certainly if you'll power down the box or unplug Ethernet it is possible to migrate live calls to some other box. I'd just like to have HA that works everytime and everywhere and try to poke some holes in reasoning in hope it'll help to reach better solution. 2013/2/12 Ben Langfeld <ben@langfeld.co.uk>:
Marcin, have you used commercial platforms that do this kind of live-call failover? They work very well. "impossible", certainly not.
Regards, Ben Langfeld
On 12 February 2013 21:33, Marcin Gozdalik <gozdal@gmail.com> wrote:
2013/2/12 Michael Collins <msc@freeswitch.org>:
If there was a readily available resource agent for FS it is "easy" to setup Corosync (if you know hat you are doing). I didn't setup Corosync to handle FS, I have OpenSIPS as SBC before FS which handles HA. Of course it is not ideal, as in case of a problem current calls are lost.
Which is precisely the point - this is *HIGH* availability we're talking about, not "kinda quickly recovering from a problem but it's okay to lose the calls that were in progress as long as our VoIP comes back up within 5-10 seconds."
We're talking about the Holy Grail of VoIP here - a fault-tolerant cluster of VoIP servers that can keep calls up and running even if the primary server goes down. Note that "primary server goes down" includes literally hundreds of scenarios from physical (power, network cable unplugged, HDD crash, etc.) to logical (user misconfiguration of FreeSWITCH or LAN settings, router/firewall changes, service provider goofups, FreeSWITCH core dump, a single sofia profile locked up but other FS is okay, etc.) I'll bet Eliot can name dozens of them off the top of his head. ;)
I have a sneaking suspicion that not everyone in this thread is thinking the same thing when we say "HA". Eliot's proposed solution encompasses fault scenarios that some of us haven't even dreamed of. I am open to someone getting P + C to do everything that Eliot's mod_ha_cluster can do but I suspect it isn't realistic. If you can prove me wrong on that then please by all means do so.
The Holy Grail you're describing is probably impossible to achieve (even Google sometimes serves you 500, just press reload to be routed to another server :). Maybe this discussion could continue to prepare some kind of a blueprint describing the predicted failure scenarios and how the proposed solution would deal with them? There are several solutions best suited for different classes of availability you're willing to tolerate.
-- Marcin Gozdalik
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-- Marcin Gozdalik