NAME
   AnyEvent::SNMP - adaptor to integrate Net::SNMP into AnyEvent.

SYNOPSIS
    use AnyEvent::SNMP;
    use Net::SNMP;

    # just use Net::SNMP and AnyEvent as you like:

    # use a condvar to transfer results, this is
    # just an example, you can use a naked callback as well.
    my $cv = AnyEvent->condvar;

    # ... start non-blocking snmp request(s)...
    Net::SNMP->session (-hostname => "127.0.0.1",
                        -community => "public",
                        -nonblocking => 1)
             ->get_request (-callback => sub { $cv->send (@_) });

    # ... do something else until the result is required
    my @result = $cv->wait;

DESCRIPTION
   This module implements an alternative "event dispatcher" for Net::SNMP,
   using AnyEvent as a backend. This integrates Net::SNMP into AnyEvent.
   That means you can make non-blocking Net::SNMP calls and as long as
   other parts of your program also use AnyEvent (or some event loop
   supported by AnyEvent), they will run in parallel.

   Also, the Net::SNMP scheduler is very inefficient with respect to both
   CPU and memory usage. Most AnyEvent backends (including the pure-perl
   backend) fare much better than the Net::SNMP dispatcher.

   Another major added feature of this module over Net::SNMP is automatic
   rate-adjustments: Net::SNMP is so slow that firing a few thousand
   requests can cause many timeouts simply because Net::SNMP cannot process
   the replies in time. This module automatically adapts the send rate to
   avoid false timeouts caused by slow reply processing.

   A potential disadvantage of this module is that replacing the dispatcher
   is not at all a documented thing to do, so future changes in Net::SNMP
   might break this module (or the many similar ones).

   This module does not export anything and does not require you to do
   anything special apart from loading it *before doing any non-blocking
   requests with Net::SNMP*. It is recommended but not required to load
   this module before "Net::SNMP".

GLOBAL VARIABLES
   $AnyEvent::SNMP::MAX_OUTSTANDING (default: 50, dynamic)
   AnyEvent::SNMP::set_max_outstanding $new_value
       Use this package variable to restrict the number of outstanding SNMP
       requests at any point in time.

       Net::SNMP is very fast at creating and sending SNMP requests, but
       much slower at parsing (big, bulk) responses. This makes it easy to
       request a lot of data that can take many seconds to parse.

       In the best case, this can lead to unnecessary delays (and even
       time-outs, as the data has been received but not yet processed) and
       in the worst case, this can lead to packet loss, when the receive
       queue overflows and the kernel can no longer accept new packets.

       To avoid this, you can (and should) limit the number of outstanding
       requests to a number low enough so that parsing time doesn't
       introduce noticeable delays.

       Unfortunately, this number depends not only on processing speed and
       load of the machine running Net::SNMP, but also on the network
       latency and the speed of your SNMP agents.

       AnyEvent::SNMP tries to dynamically adjust this number upwards and
       downwards.

       Increasing $MAX_OUTSTANDING will not automatically use the extra
       request slots. To increase $MAX_OUTSTANDING and make
       "AnyEvent::SNMP" make use of the extra parallelity, call
       "AnyEvent::SNMP::set_max_outstanding" with the new value, e.g.:

          AnyEvent::SNMP::set_max_outstanding 500;

       Although due to the dynamic adjustment, this might have little
       lasting effect.

       Note that you can use Net::SNMP::XS to speed up parsing of responses
       considerably.

   $AnyEvent::SNMP::MIN_RECVQUEUE (default: 8)
   $AnyEvent::SNMP::MAX_RECVQUEUE (default: 64)
       These values specify the minimum and maximum receive queue length
       (in units of one response packet).

       When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per
       iteration it will reduce $MAX_OUTSTANDING. If it handles less than
       $MIN_RECVQUEUE, it increases $MAX_OUTSTANDING.

       This has the result of adjusting the number of outstanding requests
       so that the recv queue is between the minimum and maximum, usually.

       This algorithm works reasonably well as long as the responses,
       response latencies and processing times are the same per packet on
       average.

COMPATIBILITY
   This module may be used as a drop in replacement for the
   Net::SNMP::Dispatcher in existing programs. You can still call
   "snmp_dispatcher" to start the event-loop, but then you loose the
   benefit of mixing Net::SNMP events with other events.

      use AnyEvent::SNMP;
      use Net::SNMP;

      # just use Net::SNMP as before

      # ... start non-blocking snmp request(s)...
      Net::SNMP->session (
            -hostname    => "127.0.0.1",
            -community   => "public",
            -nonblocking => 1,
         )->get_request (-callback => sub { ... });

      snmp_dispatcher;

SEE ALSO
   AnyEvent, Net::SNMP, Net::SNMP::XS, Net::SNMP::EV.

AUTHOR
    Marc Lehmann <[email protected]>
    http://home.schmorp.de/

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