Recursive bind becomes unresponsive with high load

Tony Finch dot at
Fri Apr 1 10:54:55 UTC 2016

sthaug at <sthaug at> wrote:
> Have you checked your operating system limits? One recursive client
> often means one open socket (waiting for response from authoritative
> server), i.e. one open file descriptor. If you have thousands of
> simultaneous recursive clients, you will need a correspondingly large
> file descriptor limit for the named process.

The other problem you might run into is lack of TCP ephemeral ports, due
to TIME_WAIT. But if this is a local zone you should be able to ensure
that your authoritative and recursive servers stay on UDP to avoid this
problem. (e.g. set minimal-responses on the auth server)

f.anthony.n.finch  <dot at>  -  I xn--zr8h punycode
Shannon, Rockall, Malin, Hebrides, Bailey: South 6 to gale 8, veering
southwest 5 to 7, becoming variable 3 or 4 later in Shannon. Rough or very
rough, occasionally high later in Rockall and Bailey. Rain then showers.
Moderate or poor, becoming mainly good.

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