[Pdns-users] Auth. server has poor TCP performance.

Augie Schwer augie.schwer at gmail.com
Wed Feb 13 20:56:49 UTC 2008

We have mixed use recursive servers that have both the auth. server
and the pdns recursive server; the auth. server sees the client query
first and hands it to the recursor if it doesn't have the answer; it's
in this exchange that we see the problem.

it seems that the TCP receiver can only handle one request at a time.

The problem we've seen is if one request takes a long time to get an
answer (like if the recursor takes a while to get back because the
remote name server is slow or doesn't answer), then the other requests
pile up behind it, get enough of these and the receiver stops
accepting requests all together.

It's like the single TCP thread locks a global semaphore and all the
other threads just wait for it to be done. Shouldn't the TCP threads
be able to handle multiple simultaneous connections?

We see this mostly with Microsoft mail servers who prefer TCP for everything.

Any thoughts?

Augie Schwer    -    Augie at Schwer.us    -    http://schwer.us
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