[Dovecot] Dovecot DNS queries its own host many times a second
Hi,
We have observed that Dovecot appears to make a DNS lookup of its own hostname many times a second. Each Dovecot server in our cluster appears to be doing around 50 queries per second to find out its own hostname. Rsyslog was the first thing we assumed was the cause, however stopping it did not help. Also the fact that at the time Dovecot was doing around 50 logins a second, seemed to correlate with it making these queries. Is there any reason why Dovecot would need to do a lookup of its own hosts IP address every time? Seems like a strange thing to do and not cache its own hostname.
Dominic
On 25.3.2013, at 3.07, Dominic Malolepszy <dmalolepszy@optusnet.com.au> wrote:
We have observed that Dovecot appears to make a DNS lookup of its own hostname many times a second. Each Dovecot server in our cluster appears to be doing around 50 queries per second to find out its own hostname. Rsyslog was the first thing we assumed was the cause, however stopping it did not help. Also the fact that at the time Dovecot was doing around 50 logins a second, seemed to correlate with it making these queries. Is there any reason why Dovecot would need to do a lookup of its own hosts IP address every time? Seems like a strange thing to do and not cache its own hostname.
I expected the libc to look it up from /etc/hosts directly.. Anyway, v2.2 does such caching. I'm not sure if it's worth the trouble to backport it to v2.1.
Zitat von Timo Sirainen <tss@iki.fi>:
On 25.3.2013, at 3.07, Dominic Malolepszy
<dmalolepszy@optusnet.com.au> wrote:We have observed that Dovecot appears to make a DNS lookup of its
own hostname many times a second. Each Dovecot server in our
cluster appears to be doing around 50 queries per second to find
out its own hostname. Rsyslog was the first thing we assumed was
the cause, however stopping it did not help. Also the fact that at
the time Dovecot was doing around 50 logins a second, seemed to
correlate with it making these queries. Is there any reason why
Dovecot would need to do a lookup of its own hosts IP address every
time? Seems like a strange thing to do and not cache its own
hostname.I expected the libc to look it up from /etc/hosts directly.. Anyway,
v2.2 does such caching. I'm not sure if it's worth the trouble to
backport it to v2.1.
I guess this is dependant on content in /etc/nsswitch.conf at least on
Linux, no?
Regards
Andreas
participants (3)
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Dominic Malolepszy
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lst_hoe02＠kwsoft.de
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Timo Sirainen