Server becomes unresponsive for unknown reason

[professor.bokdrol]

Thanks for you reply, I appreciate your time. I will focus my search more on
OS problems.

Juan

On Mon, Aug 9, 2010 at 11:21 PM, tsuna-2 [via Netty Forums and Mailing
Lists] <ml-node+5391548-1778539135-282487 at n2.nabble.com<ml-node%2B5391548-1778539135-282487 at n2.nabble.com>
> wrote:

> On Mon, Aug 9, 2010 at 1:17 PM, professor.bokdrol
> <[hidden email] <http://user/SendEmail.jtp?type=node&node=5391548&i=0>>
> wrote:
> > My application just fails to respond to SYN packets from remote hosts.
> > Locally connections are established quite fine.
>
> Your application doesn't directly control responses to SYN packets,
> the Linux kernel does.  If you don't see an ACK to the initial SYN
> packet, it could indicate that your application isn't accept()ing
> connections fast enough.  Modern Linux kernels tend to have SYN
> cookies enabled, which allows them to ACK the initial SYN even though
> your application isn't ready to accept() the socket.  When they do,
> you'll typically see a message in syslog (or kern.log, depending on
> your distro).  If you don't have SYN cookies enabled, the kernel will
> just discard the SYN packet and the kernel of the client will retry
> after its timeout has expired.
>
> I'm not familiar enough with the low level details of Netty to know
> how Netty is accept()ing new sockets but if you somehow prevent the
> code that runs accept() from running, or don't run it fast enough
> while a tons of connections are being established to your application,
> this can happen.  Also, you can configure how many sockets the kernel
> will "buffer" for you until you accept() them, this is normally done
> via the listen() system call, but I have no idea how this is done in
> Java (if it's even possible) and whether Netty exposes this somehow/
>
> It's not an accept() problem, then the problem is not related to your
> application and comes from somewhere else in the networking stack.
>
> --
> Benoit "tsuna" Sigoure
> Software Engineer @ www.StumbleUpon.com
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