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Re: squid, DNS and no buffer space



On Tue, 3 Dec 2024, Lloyd Parkes wrote:
On Mon, 2024-12-02 at 15:11 +0000, Stephen Borrill wrote:
On a busy squid proxy server, users are seeing performance problems
and
squid is logging the following:

2024/12/02 15:00:06 kid1| comm_udp_sendto FD 9, (family=2)
127.0.0.1:53: (55) No buffer space available
2024/12/02 15:00:06 kid1| idnsSendQuery FD 9: sendto: (55) No buffer
space available


Now I remember, I have seen this before. BIND assumes it's running as a
forwarder for an ISP and that it will therefore be expected to cache
the entire Internet's DNS. It will use all available memory.

I had to add the following

	max-cache-size 25%;

to the options block in my named.conf to get reasonable behaviour on my
multi-purpose server.

I did look at top at the time to see if named was being particularly greedy, but didn't spot anything. I will look more closely next time, but interactively I don't recall any delay doing DNS lookups.

Changing that setting is a good shout though. One of my co-workers was using our internal resursive DNS to clean a huge domain blacklist and
hit exactly the problem you describe.

--
Stephen



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