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Hello,
On Mon, 29 Jan 2001, Kyle Sparger wrote:
> How about selecting a new server for the connection, and signalling (not
> necessarily via signals, mind you...) to a user-space program that the
> target should immediately be checked for availability? Then the userspace
> program can set up checks to be run, and re-add it later when it becomes
> available again -- assuming it really is unavailable.
My first thought is that this can be very complex. I don't
have good ideas.
> If the server _is_ available, and acting normally, it should respond in
> the first place, though, right? :)
>
> This method might be more efficient than the existing scheduled poll
> method, but I'm sure it also has hidden traps.
Agreed. If you have many real servers the L4 checks can eat
many CPU cycles in the director.
There can be another model: register for information
in a real server agent who will notify the director with one
packet (on each 1 to 5 seconds): "All my real services are OK".
If some real service is stopped it is reported. If the host is down
or busy and the agent can't report "I'm alive" for specific time
all real services can be removed from the director user space cluster
software. Of course, this is dangerous if the kernel kills your agent
on OOM ("thanks" to the new OOM killers) but everything can happen.
20 real servers reporting info on each 2 seconds means 10p/sec
which is a low value. With this packet we can even report the weight(s)
for the real services and to use it as iamalive reply.
BTW, I'm working on such system but am too busy with other
things. I'll try to implement the basics and then other people can
extend it.
> Thanks,
>
> Kyle Sparger - Senior System Administrator
> Dialtone Internet - Extremely Fast Web Systems
> (954) 581-0097 x 122 - Voice (954) 581-7629 - Fax
> ksparger@xxxxxxxxxxxxxxxxxxxx
> http://www.dialtoneinternet.net
> "Forget college, I'm going pro."
Regards
--
Julian Anastasov <ja@xxxxxx>
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