[Serusers] Questions about ser

[Michael Ulitskiy]

On Monday 25 July 2005 01:47 pm, Michael Ulitskiy wrote:
> > > > > >   No, you don't need hundreds of children, usualy 16 is maximu what you
> > > > > >   need. Newer ser versions contain connection pool, so each child will
> > > > > >   open exactly one database connection and it will be reused across
> > > > > >   modules.
> > > > > 
> > > > > What about processing that involves slow DNS queries? I thought this would
> > > > > eat up available workers quite quickly and further processing will be blocked?
> > > > > Please correct me if I'm wrong.
> > > > 
> > > >   You can install local (running on the same host as the proxy) DNS
> > > >   cache that can also cache negative entries (those that do not exist or
> > > >   cannot be looked up), such as dnsmasq. This way the slow query would
> > > >   be performed once and subsequent queries will be answered from the
> > > >   cache.
> > > >   Moreover, kernel maintains a queue of incoming SIP requests and it
> > > >   will continue receiving SIP messages even if all processes are
> > > >   blocked. The kernel starts to drop incoming SIP messages once the
> > > >   queue is full.
> > > 
> > > Well, I guess it's not a solution. It's a workaround at best. I'd vote for something
> > > apache-like. I.e. master process monitoring the number of idle children and forking
> > > additional as needed. Thanks anyway.
> > 
> > Why not start them all from the beginning? Is not like they will eat a
> > lot of resources...
  
Just because sometimes it's hard to predict how many of them will be needed.
And if you grow over time you have a good chance not to notice that the number
needs to be increased until you get a whole lot of customers complaints. And
with this approach it's hard to deal with temporary activity spikes. And probably
more :)
  
> > > Also could you (or someone) give me a rough estimation on what is the optimal 
> > > number of children to serve let's say 10k sip clients as registrar and proxy with 
> > > moderately complex config file, but not involving DNS queries? INVITEs may involve
> > > several database queries to a dedicated database server. I understand that the
> > > question is rather vague, I'm just interested in a rough estimation and some 
> > > real-world numbers people use.
> > 
> > Try it and if you can see packets in the socket buffers (netstat)
> > increase the number of children.
> > I would use 20-50 children. The "lots of db connections" problem is
> > solved when using connection pools (or by increasing the maximum
> > connections in mysql's config :-)).
> 
Unfortunately this is not an option for postgres at the moment or I'd definitely
go for it. This is actually was the real reason I started this thread. Due to lack
of connection pool for postgres I need to determine the optimal number
of children. Thanks for the estimation.
 
> > You could use also tune the dns timeout (limit the maximum time a dns
> >  request can take). For this you would need either unstable (grep NEWS
> >  for dns_) or to edit your /etc/resolv.conf and set the timeout and
> >  attempts options  and remove the search or domain lines.
> >
> > Andrei
 
Michael