AnyEvent-SNMP/SNMP.pm

=head1 NAME

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

=head1 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;

=head1 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 I<before doing any non-blocking
requests with Net::SNMP>. It is recommended but not required to load this
module before C<Net::SNMP>.

=head1 GLOBAL VARIABLES

=over 4

=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic)

=item 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 C<$MAX_OUTSTANDING> will not automatically use the
extra request slots. To increase C<$MAX_OUTSTANDING> and make
C<AnyEvent::SNMP> make use of the extra parallelity, call
C<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 L<Net::SNMP::XS> to speed up parsing of responses
considerably.

=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<8>)

=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<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.

=back

=head1 COMPATIBILITY

This module may be used as a drop in replacement for the
Net::SNMP::Dispatcher in existing programs. You can still call
C<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;

=cut

package AnyEvent::SNMP;

use common::sense;

# it is possible to do this without loading
# Net::SNMP::Dispatcher, but much more awkward.
use Net::SNMP::Dispatcher;

# we could inherit fro Net:SNMP::Dispatcher, but since this is undocumented,
# I'd rather see it die (and reported) than silenty and subtly fail.
*msg_handle_alloc = \&Net::SNMP::Dispatcher::msg_handle_alloc;

sub Net::SNMP::Dispatcher::instance {
   AnyEvent::SNMP::
}

use Net::SNMP ();
use AnyEvent ();

our $VERSION = '6.02';

$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;

our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;

our $BUSY;
our $DONE; # finished all jobs
our @TRANSPORT; # fileno => [count, watcher]
our @QUEUE;
our $MAX_OUTSTANDING = 50;
our $MIN_RECVQUEUE   =  8;
our $MAX_RECVQUEUE   = 64;

sub kick_job;

sub _send_pdu {
   my ($pdu, $retries) = @_;

   # mostly copied from Net::SNMP::Dispatch

   # Pass the PDU to Message Processing so that it can
   # create the new outgoing message.
   my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu);

   if (!defined $msg) {
      --$BUSY;
      kick_job;
      # Inform the command generator about the Message Processing error.
      $pdu->status_information ($MESSAGE_PROCESSING->error);
      return; 
   }

   # Actually send the message.
   if (!defined $msg->send) {
      $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id)
         if $pdu->expect_response;

      # A crude attempt to recover from temporary failures.
      if ($retries-- > 0 && ($!{EAGAIN} || $!{EWOULDBLOCK} || $!{ENOSPC})) {
         my $retry_w; $retry_w = AE::timer $pdu->timeout, 0, sub {
            undef $retry_w;
            _send_pdu ($pdu, $retries);
         };
      } else {
         --$BUSY;
         kick_job;
      }

      # Inform the command generator about the send() error.
      $pdu->status_information ($msg->error);
      return;
   }

   # Schedule the timeout handler if the message expects a response.
   if ($pdu->expect_response) {
      my $transport = $msg->transport;
      my $fileno    = $transport->fileno;

      # register the transport
      unless ($TRANSPORT[$fileno][0]++) {
         $TRANSPORT[$fileno][1] = AE::io $transport->socket, 0, sub {
            for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go
               # Create a new Message object to receive the response
               my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport);

               if (!defined $msg) {
                  die sprintf 'Failed to create Message object [%s]', $error;
               }

               # Read the message from the Transport Layer
               if (!defined $msg->recv) {
                  if ($transport->connectionless) {
                     # if we handled very few replies and we have queued work, try
                     # to increase the parallelity as we probably can handle more.
                     if ($count < $MIN_RECVQUEUE && @QUEUE) {
                        ++$MAX_OUTSTANDING;
                        kick_job;
                     }
                  } else {
                     # for some reason, connected-oriented transports seem to need this
                     delete $TRANSPORT[$fileno]
                        unless --$TRANSPORT[$fileno][0];
                  }

                  $msg->error;
                  return;
               }

               # For connection-oriented Transport Domains, it is possible to
               # "recv" an empty buffer if reassembly is required.
               if (!$msg->length) {
                  return;
               }

               # Hand the message over to Message Processing.
               if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
                  $MESSAGE_PROCESSING->error;
                  return;
               }

               # Set the error if applicable.
               $msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;

               # Notify the command generator to process the response.
               # Net::SNMP calls process_response_pdu, which simply calls callback_execute,
               # but some errors cause $msg to be of type Net::SNMP::Message, not Net::SMMP::PDU,
               # so we call the underlying callback_execute method which exists on both and
               # seems to do the right thing.
               $msg->callback_execute;

               # Cancel the timeout.
               my $rtimeout_w = $msg->timeout_id;
               if ($$rtimeout_w) {
                  undef $$rtimeout_w;

                  --$BUSY;
                  kick_job;

                  unless (--$TRANSPORT[$fileno][0]) {
                     delete $TRANSPORT[$fileno];
                     return;
                  }
               }
            }

            # when we end up here, we successfully handled $MAX_RECVQUEUE
            # replies in one iteration, so assume we are overloaded
            # and reduce the amount of parallelity.
            $MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.95) || 1;
         };
      }

      $msg->timeout_id (\(my $rtimeout_w =
         AE::timer $pdu->timeout, 0, sub {
            my $rtimeout_w = $msg->timeout_id;
            if ($$rtimeout_w) {
               undef $$rtimeout_w;
               delete $TRANSPORT[$fileno]
                  unless --$TRANSPORT[$fileno][0];
            }

            if ($retries--) {
               _send_pdu ($pdu, $retries);
            } else {
               $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id);
               $pdu->status_information ("No response from remote host '%s'", $pdu->hostname);

               --$BUSY;
               kick_job;
            }
         })
      ); 
   } else {
     --$BUSY;
     kick_job;
   }
}

sub kick_job {
   while ($BUSY < $MAX_OUTSTANDING) {
      my $pdu = shift @QUEUE
         or last;

      ++$BUSY;
      _send_pdu $pdu, $pdu->retries;
   }

   $DONE and $DONE->() unless $BUSY;
}

sub send_pdu($$$) {
   my (undef, $pdu, $delay) = @_;

   # $delay is not very sensibly implemented by AnyEvent::SNMP,
   # but apparently it is not a very sensible feature.
   if ($delay > 0) {
      ++$BUSY;
      my $delay_w; $delay_w = AE::timer $delay, 0, sub {
         undef $delay_w;
         push @QUEUE, $pdu;
         --$BUSY;
         kick_job;
      };
      return 1;
   }

   push @QUEUE, $pdu;
   kick_job;

   1
}

sub loop($) {
   while ($BUSY) {
      $DONE = AE::cv;
      $DONE->recv;
      undef $DONE;
   }
}

*activate = \&loop; # 5.x compatibility?
*listen   = \&loop; # 5.x compatibility?

sub one_event($) {
   # should not ever be used
   AnyEvent->one_event; #d# todo
}

sub set_max_outstanding($) {
   $MAX_OUTSTANDING = $_[0];
   kick_job;
}

# not provided yet:
# schedule            # apparently only used by Net::SNMP::Dispatcher itself
# register            # apparently only used by Net::SNMP::Dispatcher itself
# deregister          # apparently only used by Net::SNMP::Dispatcher itself
# cancel              # apparently only used by Net::SNMP::Dispatcher itself
# return_response_pdu # apparently not used at all?
# error               # only used by Net::SNMP::Dispatcher itself?
# debug               # only used by Net::SNMP::Dispatcher itself?

=head1 SEE ALSO

L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1

Revision:	1.14
Committed:	Wed Oct 9 18:22:59 2019 UTC (6 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	rel-6_02, HEAD
Changes since 1.13:	+6 -2 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	AnyEvent::SNMP - adaptor to integrate Net::SNMP into AnyEvent.
4
5	=head1 SYNOPSIS
6
7	use AnyEvent::SNMP;
8	use Net::SNMP;
9
10	# just use Net::SNMP and AnyEvent as you like:
11
12	# use a condvar to transfer results, this is
13	# just an example, you can use a naked callback as well.
14	my $cv = AnyEvent->condvar;
15
16	# ... start non-blocking snmp request(s)...
17	Net::SNMP->session (-hostname => "127.0.0.1",
18	-community => "public",
19	-nonblocking => 1)
20	->get_request (-callback => sub { $cv->send (@_) });
21
22	# ... do something else until the result is required
23	my @result = $cv->wait;
24
25	=head1 DESCRIPTION
26
27	This module implements an alternative "event dispatcher" for Net::SNMP,
28	using AnyEvent as a backend. This integrates Net::SNMP into AnyEvent. That
29	means you can make non-blocking Net::SNMP calls and as long as other
30	parts of your program also use AnyEvent (or some event loop supported by
31	AnyEvent), they will run in parallel.
32
33	Also, the Net::SNMP scheduler is very inefficient with respect to both CPU
34	and memory usage. Most AnyEvent backends (including the pure-perl backend)
35	fare much better than the Net::SNMP dispatcher.
36
37	Another major added feature of this module over Net::SNMP is automatic
38	rate-adjustments: Net::SNMP is so slow that firing a few thousand
39	requests can cause many timeouts simply because Net::SNMP cannot process
40	the replies in time. This module automatically adapts the send rate to
41	avoid false timeouts caused by slow reply processing.
42
43	A potential disadvantage of this module is that replacing the dispatcher
44	is not at all a documented thing to do, so future changes in Net::SNMP
45	might break this module (or the many similar ones).
46
47	This module does not export anything and does not require you to do
48	anything special apart from loading it I<before doing any non-blocking
49	requests with Net::SNMP>. It is recommended but not required to load this
50	module before C<Net::SNMP>.
51
52	=head1 GLOBAL VARIABLES
53
54	=over 4
55
56	=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic)
57
58	=item AnyEvent::SNMP::set_max_outstanding $new_value
59
60	Use this package variable to restrict the number of outstanding SNMP
61	requests at any point in time.
62
63	Net::SNMP is very fast at creating and sending SNMP requests, but much
64	slower at parsing (big, bulk) responses. This makes it easy to request a
65	lot of data that can take many seconds to parse.
66
67	In the best case, this can lead to unnecessary delays (and even time-outs,
68	as the data has been received but not yet processed) and in the worst
69	case, this can lead to packet loss, when the receive queue overflows and
70	the kernel can no longer accept new packets.
71
72	To avoid this, you can (and should) limit the number of outstanding
73	requests to a number low enough so that parsing time doesn't introduce
74	noticeable delays.
75
76	Unfortunately, this number depends not only on processing speed and load
77	of the machine running Net::SNMP, but also on the network latency and the
78	speed of your SNMP agents.
79
80	AnyEvent::SNMP tries to dynamically adjust this number upwards and
81	downwards.
82
83	Increasing C<$MAX_OUTSTANDING> will not automatically use the
84	extra request slots. To increase C<$MAX_OUTSTANDING> and make
85	C<AnyEvent::SNMP> make use of the extra parallelity, call
86	C<AnyEvent::SNMP::set_max_outstanding> with the new value, e.g.:
87
88	AnyEvent::SNMP::set_max_outstanding 500;
89
90	Although due to the dynamic adjustment, this might have little lasting
91	effect.
92
93	Note that you can use L<Net::SNMP::XS> to speed up parsing of responses
94	considerably.
95
96	=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<8>)
97
98	=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>)
99
100	These values specify the minimum and maximum receive queue length (in
101	units of one response packet).
102
103	When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per iteration
104	it will reduce $MAX_OUTSTANDING. If it handles less than $MIN_RECVQUEUE,
105	it increases $MAX_OUTSTANDING.
106
107	This has the result of adjusting the number of outstanding requests so that
108	the recv queue is between the minimum and maximum, usually.
109
110	This algorithm works reasonably well as long as the responses, response
111	latencies and processing times are the same per packet on average.
112
113	=back
114
115	=head1 COMPATIBILITY
116
117	This module may be used as a drop in replacement for the
118	Net::SNMP::Dispatcher in existing programs. You can still call
119	C<snmp_dispatcher> to start the event-loop, but then you loose the benefit
120	of mixing Net::SNMP events with other events.
121
122	use AnyEvent::SNMP;
123	use Net::SNMP;
124
125	# just use Net::SNMP as before
126
127	# ... start non-blocking snmp request(s)...
128	Net::SNMP->session (
129	-hostname => "127.0.0.1",
130	-community => "public",
131	-nonblocking => 1,
132	)->get_request (-callback => sub { ... });
133
134	snmp_dispatcher;
135
136	=cut
137
138	package AnyEvent::SNMP;
139
140	use common::sense;
141
142	# it is possible to do this without loading
143	# Net::SNMP::Dispatcher, but much more awkward.
144	use Net::SNMP::Dispatcher;
145
146	# we could inherit fro Net:SNMP::Dispatcher, but since this is undocumented,
147	# I'd rather see it die (and reported) than silenty and subtly fail.
148	*msg_handle_alloc = \&Net::SNMP::Dispatcher::msg_handle_alloc;
149
150	sub Net::SNMP::Dispatcher::instance {
151	AnyEvent::SNMP::
152	}
153
154	use Net::SNMP ();
155	use AnyEvent ();
156
157	our $VERSION = '6.02';
158
159	$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
160
161	our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
162
163	our $BUSY;
164	our $DONE; # finished all jobs
165	our @TRANSPORT; # fileno => [count, watcher]
166	our @QUEUE;
167	our $MAX_OUTSTANDING = 50;
168	our $MIN_RECVQUEUE = 8;
169	our $MAX_RECVQUEUE = 64;
170
171	sub kick_job;
172
173	sub _send_pdu {
174	my ($pdu, $retries) = @_;
175
176	# mostly copied from Net::SNMP::Dispatch
177
178	# Pass the PDU to Message Processing so that it can
179	# create the new outgoing message.
180	my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu);
181
182	if (!defined $msg) {
183	--$BUSY;
184	kick_job;
185	# Inform the command generator about the Message Processing error.
186	$pdu->status_information ($MESSAGE_PROCESSING->error);
187	return;
188	}
189
190	# Actually send the message.
191	if (!defined $msg->send) {
192	$MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id)
193	if $pdu->expect_response;
194
195	# A crude attempt to recover from temporary failures.
196	if ($retries-- > 0 && ($!{EAGAIN} \|\| $!{EWOULDBLOCK} \|\| $!{ENOSPC})) {
197	my $retry_w; $retry_w = AE::timer $pdu->timeout, 0, sub {
198	undef $retry_w;
199	_send_pdu ($pdu, $retries);
200	};
201	} else {
202	--$BUSY;
203	kick_job;
204	}
205
206	# Inform the command generator about the send() error.
207	$pdu->status_information ($msg->error);
208	return;
209	}
210
211	# Schedule the timeout handler if the message expects a response.
212	if ($pdu->expect_response) {
213	my $transport = $msg->transport;
214	my $fileno = $transport->fileno;
215
216	# register the transport
217	unless ($TRANSPORT[$fileno][0]++) {
218	$TRANSPORT[$fileno][1] = AE::io $transport->socket, 0, sub {
219	for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go
220	# Create a new Message object to receive the response
221	my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport);
222
223	if (!defined $msg) {
224	die sprintf 'Failed to create Message object [%s]', $error;
225	}
226
227	# Read the message from the Transport Layer
228	if (!defined $msg->recv) {
229	if ($transport->connectionless) {
230	# if we handled very few replies and we have queued work, try
231	# to increase the parallelity as we probably can handle more.
232	if ($count < $MIN_RECVQUEUE && @QUEUE) {
233	++$MAX_OUTSTANDING;
234	kick_job;
235	}
236	} else {
237	# for some reason, connected-oriented transports seem to need this
238	delete $TRANSPORT[$fileno]
239	unless --$TRANSPORT[$fileno][0];
240	}
241
242	$msg->error;
243	return;
244	}
245
246	# For connection-oriented Transport Domains, it is possible to
247	# "recv" an empty buffer if reassembly is required.
248	if (!$msg->length) {
249	return;
250	}
251
252	# Hand the message over to Message Processing.
253	if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
254	$MESSAGE_PROCESSING->error;
255	return;
256	}
257
258	# Set the error if applicable.
259	$msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;
260
261	# Notify the command generator to process the response.
262	# Net::SNMP calls process_response_pdu, which simply calls callback_execute,
263	# but some errors cause $msg to be of type Net::SNMP::Message, not Net::SMMP::PDU,
264	# so we call the underlying callback_execute method which exists on both and
265	# seems to do the right thing.
266	$msg->callback_execute;
267
268	# Cancel the timeout.
269	my $rtimeout_w = $msg->timeout_id;
270	if ($$rtimeout_w) {
271	undef $$rtimeout_w;
272
273	--$BUSY;
274	kick_job;
275
276	unless (--$TRANSPORT[$fileno][0]) {
277	delete $TRANSPORT[$fileno];
278	return;
279	}
280	}
281	}
282
283	# when we end up here, we successfully handled $MAX_RECVQUEUE
284	# replies in one iteration, so assume we are overloaded
285	# and reduce the amount of parallelity.
286	$MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.95) \|\| 1;
287	};
288	}
289
290	$msg->timeout_id (\(my $rtimeout_w =
291	AE::timer $pdu->timeout, 0, sub {
292	my $rtimeout_w = $msg->timeout_id;
293	if ($$rtimeout_w) {
294	undef $$rtimeout_w;
295	delete $TRANSPORT[$fileno]
296	unless --$TRANSPORT[$fileno][0];
297	}
298
299	if ($retries--) {
300	_send_pdu ($pdu, $retries);
301	} else {
302	$MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id);
303	$pdu->status_information ("No response from remote host '%s'", $pdu->hostname);
304
305	--$BUSY;
306	kick_job;
307	}
308	})
309	);
310	} else {
311	--$BUSY;
312	kick_job;
313	}
314	}
315
316	sub kick_job {
317	while ($BUSY < $MAX_OUTSTANDING) {
318	my $pdu = shift @QUEUE
319	or last;
320
321	++$BUSY;
322	_send_pdu $pdu, $pdu->retries;
323	}
324
325	$DONE and $DONE->() unless $BUSY;
326	}
327
328	sub send_pdu($$$) {
329	my (undef, $pdu, $delay) = @_;
330
331	# $delay is not very sensibly implemented by AnyEvent::SNMP,
332	# but apparently it is not a very sensible feature.
333	if ($delay > 0) {
334	++$BUSY;
335	my $delay_w; $delay_w = AE::timer $delay, 0, sub {
336	undef $delay_w;
337	push @QUEUE, $pdu;
338	--$BUSY;
339	kick_job;
340	};
341	return 1;
342	}
343
344	push @QUEUE, $pdu;
345	kick_job;
346
347	1
348	}
349
350	sub loop($) {
351	while ($BUSY) {
352	$DONE = AE::cv;
353	$DONE->recv;
354	undef $DONE;
355	}
356	}
357
358	*activate = \&loop; # 5.x compatibility?
359	*listen = \&loop; # 5.x compatibility?
360
361	sub one_event($) {
362	# should not ever be used
363	AnyEvent->one_event; #d# todo
364	}
365
366	sub set_max_outstanding($) {
367	$MAX_OUTSTANDING = $_[0];
368	kick_job;
369	}
370
371	# not provided yet:
372	# schedule # apparently only used by Net::SNMP::Dispatcher itself
373	# register # apparently only used by Net::SNMP::Dispatcher itself
374	# deregister # apparently only used by Net::SNMP::Dispatcher itself
375	# cancel # apparently only used by Net::SNMP::Dispatcher itself
376	# return_response_pdu # apparently not used at all?
377	# error # only used by Net::SNMP::Dispatcher itself?
378	# debug # only used by Net::SNMP::Dispatcher itself?
379
380	=head1 SEE ALSO
381
382	L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.
383
384	=head1 AUTHOR
385
386	Marc Lehmann <schmorp@schmorp.de>
387	http://home.schmorp.de/
388
389	=cut
390
391	1
392