Determening the number of clients per KDC

[Russ Allbery]

Sergei Gerasenko <gerases at gmail.com> writes:

> Thanks for the quick response, Russ. Let’s say I run 1 worker
> process. How many clients can that sustain in the worst case scenario of
> all the clients trying to get a ticket? I need some way to quantify
> this. As for failover, I am planning to deploy a standby node.

It's unfortunately been long enough since I've tested this on a system
running flat out that I don't remember what qps a KDC can do on modern
hardware, but I would expect it to at least be in the range of 100 qps.
It's probably constrained by the KDC being single-threaded.  Clients
aren't going to generally all try to get a ticket at the same time, due to
ticket caching, so that scales to a lot of clients.

General rule of thumb for KDCs is that you want at least a master and a
replica, and there's no reason not to have the replica serve most of the
traffic (in other words, I wouldn't go with a standby design).  Usually I
run at least three KDCs, although the number three is mostly because I
started with kaserver that needed three KDCs for stable Ubik quorum, which
of course isn't a thing with regular KDCs, so I don't know that three is
really better than two.

-- 
Russ Allbery (eagle at eyrie.org)              <http://www.eyrie.org/~eagle/>