Re: PoCo::Client::Ping intermittently fails to emit pings

ICMP is not a reliable network protocol.  IP is allowed to drop the  
packets without notice.  The only way to detect the case is when too  
much time has elapsed without a response---$timeout is reached.

Enqueuing your request in the event queue is not the same thing as  
sending an ICMP packet.  post() may succeed where the ping fails.

-- 
Rocco Caputo - [email protected]


On Apr 19, 2009, at 12:44, Stuart Kendrick wrote:

> If the OS fails to execute a ping, does there exist a mechanism for  
> the OS to tell POE about that?  And for me to 'notice' such an  
> incident?
>
> I was hoping that checking the return value on a 'post' would do  
> that ... but thus far, no dice (i.e. the box on which my script is  
> running intermittently fails to emit pings, but by script doesn't  
> log anything.)
>
> [...]
>    # "Pinger, do a ping and return the results as a pong event.  The
>    # address to ping is $addr."
>    $result = $kernel->post(  'pinger',
>                              'ping',
>                              'pong',
>                              $addr,
>                              $timeout,
>                            );
>    log_error("Problem pinging $addr: $!") unless $result;
> [...]
>
> From http://search.cpan.org/~rcaputo/POE-1.004/lib/POE/Kernel.pm#post_DESTINATION,_EVENT_NAME_ 
> [,_PARAMETER_LIST]
>
> "post() returns a Boolean value indicating whether the message was  
> successfully enqueued. If post() returns false, $! is set to explain  
> the failure:"
>
> --sk
>
>
> Stuart Kendrick wrote:
>> my favorite pinging application (in-house app, uses  
>> POE::Component::Client::Ping) intermittently reports a rash of  
>> missed replies. happens roughly the same time each night; the  
>> condition lasts for several minutes