I think dup2() inside IO::Socket::IP may cause this
problem:
https://metacpan.org/source/PEVANS/IO-Socket-IP-0.37/lib/IO/Socket/IP.pm#L916
socket 3 was added to epoll, then socket 4 was duplicated to socket 3, I
think epoll may not like
this:
http://stackoverflow.com/questions/27948251/why-epoll-wait-doesnt-react-on-dup2writable-fd-non-writable-fd
On Wednesday, September 9, 2015 at 8:42:59 PM UTC+6, Хозов Андрей wrote:
>
> I have a strange behavior Mojo::IOLoop::Client while connect to localhost
> when it resolves in two addresses.
>
> *$ host localhost*
> localhost has address 127.0.0.1
> localhost has IPv6 address ::1
> *$*
>
> When using EV via select or poll or Mojo::Reactor::Poll all is ok. But
> when using EV via epoll I get the error "connect timeout".
>
> *$ LIBEV_FLAGS=2 strace perl -MMojo::IOLoop -le
> 'Mojo::IOLoop->client({address => "localhost", port => 27017}, sub { my
> ($l, $err, $stream) = @_; warn $err; Mojo::IOLoop->stop });
> Mojo::IOLoop->start'*
> socket(PF_INET6, SOCK_STREAM, IPPROTO_TCP) = 3
> ...
> connect(3, {sa_family=AF_INET6, sin6_port=htons(27017),
> inet_pton(AF_INET6, "::1", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0},
> 28) = -1 EINPROGRESS (Operation now in progress)
> fcntl(3, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)
> *poll([{fd=5, events=POLLIN}, {fd=3, events=POLLOUT}], 2, 9996) = 1
> ([{fd=3, revents=POLLOUT|POLLERR|POLLHUP}])*
> getsockopt(3, SOL_SOCKET, SO_ERROR, [111], [4]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 4
> ...
> dup2(4, 3) = 3
> close(4) = 0
> fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
> fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
> connect(3, {sa_family=AF_INET, sin_port=htons(27017),
> sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in
> progress)
> *poll([{fd=5, events=POLLIN}, {fd=3, events=POLLOUT}], 2, 9996) = 1
> ([{fd=3, revents=POLLOUT}])*
> getsockopt(3, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
> connect(3, {sa_family=AF_INET, sin_port=htons(27017),
> sin_addr=inet_addr("127.0.0.1")}, 16) = 0
> getpeername(3, {sa_family=AF_INET, sin_port=htons(27017),
> sin_addr=inet_addr("127.0.0.1")}, [16]) = 0
> setsockopt(3, SOL_TCP, TCP_NODELAY, [1], 4) = 0
> ...
>
> *$ LIBEV_FLAGS=4 strace perl -MMojo::IOLoop -le
> 'Mojo::IOLoop->client({address => "localhost", port => 27017}, sub { my
> ($l, $err, $stream) = @_; warn $err if $err; Mojo::IOLoop->stop });
> Mojo::IOLoop->start'*
> socket(PF_INET6, SOCK_STREAM, IPPROTO_TCP) = 3
> ...
> connect(3, {sa_family=AF_INET6, sin6_port=htons(27017),
> inet_pton(AF_INET6, "::1", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0},
> 28) = -1 EINPROGRESS (Operation now in progress)
> fcntl(3, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)
> epoll_ctl(5, EPOLL_CTL_ADD, 3, {EPOLLOUT, {u32=3, u64=4294967299}}) = 0
> *epoll_wait(5, {{EPOLLOUT|EPOLLERR|EPOLLHUP, {u32=3, u64=4294967299}}},
> 64, 9996) = 1*
> epoll_ctl(5, EPOLL_CTL_MOD, 3, {EPOLLOUT, {u32=3, u64=4294967299}}) = 0
> getsockopt(3, SOL_SOCKET, SO_ERROR, [111], [4]) = 0
> socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 4
> ...
> dup2(4, 3) = 3
> close(4) = 0
> fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
> fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
> connect(3, {sa_family=AF_INET, sin_port=htons(27017),
> sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in
> progress)
> *epoll_wait(5, {}, 64, 9995) = 0*
> write(2, "Connect timeout at -e line 1, <D"..., 48Connect timeout at -e
> line 1, <DATA> line 2231.
> ...
>
>
> I see that the second time epoll_wait is not monitoring the descriptor(3)
> and therefore a connect event is missing.
> Can you explain me this behavior?
>
>
> --
> Andrey Khozov
>
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