Re: _ping_more / dropping pings

Personaly I did not like the idea of running my whole process as user root
and so implemented mass ping using Wheel::Run and fping.  Unfortunately I
don't have it wrappered up into a nice distro. But it was not too hard to
do.

On Wed, Feb 11, 2009 at 12:46 PM, <[email protected]> wrote:

> i use POE::Component::Client::Ping to emit lots of pings
>
> and i find that i have to throttle the number of pings i have
> outstanding; otherwise, POE::Component::Client::Ping doesn't see the
> responses
>
> using a sniffer (tshark running on the box hosting my script), i can
> see that the ICMP Echo Reply frames arrive just fine (as far as tshark
> is concerned)
>
> i suppose that i could be seeing an effect somewhere in the OS, such
> that if the flow of returning ICMP Echoes exceeds some threshold, the
> NIC sees them, tshark sees them ... but somewhere higher up, a buffer
> overflows and Perl never gets them
>
> or, i suppose that the flood of responses overwhelms some buffer
> inside POE::Component::Client::Ping
>
> or perhaps somewhere in between:  perhaps there is an OS buffer which
> holds the ICMP Echo Reply frames and unless POE pulls them out of the
> buffer fast enough, the buffer will overflow and POE won't see those
> responses
>
> i notice that sometimes i can get away with several hundred
> outstanding pings at once; sometimes, not much more than thirty.  i
> generally run with a ceiling of twenty (20).  the variability depends
> on load on my box?  i don't know
>
> this isn't a problem  -- the total time it takes to ping the ~350
> addresses i'm using as my test bed right now doesn't change,
> regardless of the size of my 'ping heap'
>
> but i'm curious.  would anyone know where the overflowing buffer
> lives?  if in the OS, how would i look to see its size?  of inside
> POE, again, how would i identify its size?
>
> i'm running Perl 5.8.8, POE 1.03, POE::Component::Client::Ping 1.14
> under CentOS 5.2
>
> my code is visible at https://vishnu.fhcrc.org/ping/mass-ping
>
> the 'ping_nodes' subroutine is the master pinger ... with 'sub
> _client_start', 'sub _ping_more', and 'sub _client_got_pong' playing
> the usual roles
>
> --sk
>
> stuart kendrick
> fhcrc
> seattle, wa
>
>