no more recursive clients: quota reached

[John Wobus]

Typically you can increase the default without harm, e.g., double or x  
10 if you
have a recent-vintage server with typical memory and speed, but
something might be causing the behavior that is impervious to
such a change or that needs some other kind of attention.
Such a problem might solely stem from sheer load, but quite often stems
from queries that are not receiving answers and are just sitting there
until they time out.

One of your clients might be making up names and trying them:
many would receive negative responses but a percent would receive
no response and sit.  Or it could be that some specific locally- 
popular domain's
nameservers are down or unreachable.  Or it could be intermittent  
network
problems. Or some kind of long-term routing/connectivity issue, e.g. the
consequences of firewalling.

If there are short episodes with tons of these log entries, that hints  
at
short problems with your Internet connection, or a specific app that
is causing the issue when it runs.  If your Internet connectivity
goes away in such manner that packets "disappear", then the number
of outstanding recursive queries typically steadily rises until the  
quota
is reached.

If you look at the number of clients at random times and it is always
substantial and/or close to the quota, it may be that increasing the
quota is the right solution.

rndc lets you view the outstanding queries and see how long they've
been waiting, which provides a lot of insight into what is happening.

John Wobus
Cornell IT