Dan Track wrote:
Hi
I have a problem with one of my server, where basically I get a
network hang for a few seconds every minute when communicating with
another server on the same subnet.
I caught the hang when running tnsping, and here's the strace. The
space between the strace is where I found the problem to be.
My question is can someone please help wme figure out what is going
on, and guide me to where I can read up on these system calls, like
POLLIN etc. I'd particularly would like to know what is happening
before and after the space in the strace.
[snip]
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4
connect(4, {sa_family=AF_INET, sin_port=htons(53),
This is the important bit. You've opened a UDP socket on port 53, i.e DNS and
the file descriptor used is 4.
sin_addr=inet_addr("10.11.10.1")}, 28) = 0
fcntl64(4, F_GETFL) = 0x2 (flags O_RDWR)
fcntl64(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
gettimeofday({1143022459, 869414}, NULL) = 0
poll([{fd=4, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(4, "\367\201\1\0\0\1\0\0\0\0\0\0\7neptune\2l3\next"..., 43, 0) = 43
here, it looks like it's sent a request to the DNS server...
> poll(
>
and now it's polling for the response.
My guess would be it's a delay in resolving ip/hostnames. Check you DNS settings.
--
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : nmw@xxxxxxxxxxxx
Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
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