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Re: [nmh-workers] strace show # pauses/takes 5+ sec | network issue? ( not nmh )

2019-09-09 15:17:12

nmh@trodman.com wrote:
    > I thought it might be dns. Earlier in the day, twice in a row it hung
    > near the end of this snip:

    > [...]  socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK,
    > IPPROTO_IP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(53),
    > sin_addr=inet_addr("71.19.155.120")}, 16) = 0
    > clock_gettime(CLOCK_REALTIME, {tv_sec=1567958940, tv_nsec=908626657}) =
    > 0 poll([{fd=4, events=POLLOUT}], 1, 0) = 1 ([{fd=4, revents=POLLOUT}])
    > sendmmsg(4, [{msg_hdr={msg_name=NULL, msg_namelen=0,
    > 
msg_iov=[{iov_base="\325T\1\0\0\1\0\0\0\0\0\0\5ibisbil\4mumble\3org\0\0\1\0\1",
    > iov_len=32}], msg_iovlen=1, msg_controllen=0, msg_flags=0},
    > msg_len=32}, {msg_hdr={msg_name=NULL, msg_namelen=0,
    > 
msg_iov=[{iov_base="ql\1\0\0\1\0\0\0\0\0\0\5ibisbil\4mumble\3org\0\0\34\0\1",
    > iov_len=32}], msg_iovlen=1, msg_controllen=0, msg_flags=0},
    > msg_len=32}], 2, MSG_NOSIGNAL) = 2

    > where ibisbil.mumble.com is the obfuscated hostname of the fedora vps
    > with the problem, and 71.19.155.120 is the 1st nameserver in
    > ibisbil.mumble.com:/etc/resolv.conf. Later in the day though the strace
    > stalled consistently at the spot shown in my first post.

    >> But unfortunately these system call traces are not very helpful.  This
    >> is because you are tracing the command "command", and all that shows
    >> is you execute a nmh command and it waits 5 seconds for it to
    >> complete.

    > OK/thanks. In the future I will plan to run for example:

    >     strace -o /tmp/foo -t -f /usr/local/nmh/bin/scan last

I suggest -ff, which will populate the files /tmp/foo.12343 by PID#
I can't see why scan is doing DNS, but what do I know.

If it's network related, we'll probably ask you to send tcdpump.
so:
        sudo tcpdump -i any -n -p -w /tmp/network.pcap
        
if you are logged in by SSH, then please add "not port 22"

-- 
]               Never tell me the odds!                 | ipv6 mesh networks [ 
]   Michael Richardson, Sandelman Software Works        | network architect  [ 
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [ 
        

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