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 fetaure 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::SNP
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
noticable 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 paralellity, 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 maximu, usually.

This algorithm works reasonably well as long as the responses, response
latencies and processing times are the same size 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;

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

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

our $VERSION = '1.0';

$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.
               $msg->process_response_pdu; 

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

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

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

=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:	1.11
Committed:	Sun Oct 31 18:26:27 2010 UTC (13 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.10:	+3 -4 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.7	AnyEvent::SNMP - adaptor to integrate Net::SNMP into AnyEvent.
4	root	1.1
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	root	1.10	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	root	1.1
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	root	1.10	Another major added fetaure 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::SNP
45			might break this module (or the many similar ones).
46	root	1.1
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	root	1.3	=head1 GLOBAL VARIABLES
53
54			=over 4
55
56			=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic)
57
58	root	1.6	=item AnyEvent::SNMP::set_max_outstanding $new_value
59
60	root	1.3	Use this package variable to restrict the number of outstanding SNMP
61			requests at any point in time.
62
63			Net::SNMP is very fast at creating and sending SNMP requests, but much
64			slower at parsing (big, bulk) responses. This makes it easy to request a
65			lot of data that can take many seconds to parse.
66
67			In the best case, this can lead to unnecessary delays (and even time-outs,
68			as the data has been received but not yet processed) and in the worst
69			case, this can lead to packet loss, when the receive queue overflows and
70			the kernel can no longer accept new packets.
71
72	root	1.6	To avoid this, you can (and should) limit the number of outstanding
73			requests to a number low enough so that parsing time doesn't introduce
74			noticable delays.
75	root	1.3
76			Unfortunately, this number depends not only on processing speed and load
77			of the machine running Net::SNMP, but also on the network latency and the
78			speed of your SNMP agents.
79
80	root	1.11	AnyEvent::SNMP tries to dynamically adjust this number upwards and
81			downwards.
82	root	1.3
83	root	1.6	Increasing C<$MAX_OUTSTANDING> will not automatically use the
84	root	1.8	extra request slots. To increase C<$MAX_OUTSTANDING> and make
85			C<AnyEvent::SNMP> make use of the extra paralellity, call
86	root	1.6	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	root	1.3	Note that you can use L<Net::SNMP::XS> to speed up parsing of responses
94			considerably.
95
96	root	1.5	=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<8>)
97	root	1.3
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 maximu, usually.
109
110			This algorithm works reasonably well as long as the responses, response
111			latencies and processing times are the same size 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	root	1.1	=cut
137
138			package AnyEvent::SNMP;
139
140	root	1.11	use common::sense;
141	root	1.1
142			# it is possible to do this without loading
143			# Net::SNMP::Dispatcher, but much more awkward.
144			use Net::SNMP::Dispatcher;
145
146			sub Net::SNMP::Dispatcher::instance {
147			AnyEvent::SNMP::
148			}
149
150			use Net::SNMP ();
151			use AnyEvent ();
152
153	root	1.8	our $VERSION = '1.0';
154	root	1.1
155			$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
156
157			our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
158
159			our $BUSY;
160	root	1.8	our $DONE; # finished all jobs
161	root	1.5	our @TRANSPORT; # fileno => [count, watcher]
162	root	1.3	our @QUEUE;
163			our $MAX_OUTSTANDING = 50;
164	root	1.5	our $MIN_RECVQUEUE = 8;
165	root	1.3	our $MAX_RECVQUEUE = 64;
166
167	root	1.9	sub kick_job;
168	root	1.1
169			sub _send_pdu {
170			my ($pdu, $retries) = @_;
171
172			# mostly copied from Net::SNMP::Dispatch
173
174			# Pass the PDU to Message Processing so that it can
175			# create the new outgoing message.
176			my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu);
177
178			if (!defined $msg) {
179	root	1.9	--$BUSY;
180	root	1.3	kick_job;
181	root	1.1	# Inform the command generator about the Message Processing error.
182			$pdu->status_information ($MESSAGE_PROCESSING->error);
183			return;
184			}
185
186			# Actually send the message.
187			if (!defined $msg->send) {
188			$MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id)
189			if $pdu->expect_response;
190
191			# A crude attempt to recover from temporary failures.
192			if ($retries-- > 0 && ($!{EAGAIN} \|\| $!{EWOULDBLOCK} \|\| $!{ENOSPC})) {
193	root	1.8	my $retry_w; $retry_w = AE::timer $pdu->timeout, 0, sub {
194	root	1.1	undef $retry_w;
195			_send_pdu ($pdu, $retries);
196	root	1.8	};
197	root	1.1	} else {
198	root	1.9	--$BUSY;
199	root	1.3	kick_job;
200	root	1.1	}
201
202			# Inform the command generator about the send() error.
203			$pdu->status_information ($msg->error);
204			return;
205			}
206
207			# Schedule the timeout handler if the message expects a response.
208			if ($pdu->expect_response) {
209			my $transport = $msg->transport;
210	root	1.5	my $fileno = $transport->fileno;
211	root	1.1
212			# register the transport
213	root	1.5	unless ($TRANSPORT[$fileno][0]++) {
214	root	1.8	$TRANSPORT[$fileno][1] = AE::io $transport->socket, 0, sub {
215	root	1.3	for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go
216			# Create a new Message object to receive the response
217			my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport);
218
219			if (!defined $msg) {
220			die sprintf 'Failed to create Message object [%s]', $error;
221			}
222	root	1.1
223	root	1.3	# Read the message from the Transport Layer
224			if (!defined $msg->recv) {
225			if ($transport->connectionless) {
226	root	1.4	# if we handled very few replies and we have queued work, try
227			# to increase the parallelity as we probably can handle more.
228	root	1.3	if ($count < $MIN_RECVQUEUE && @QUEUE) {
229			++$MAX_OUTSTANDING;
230			kick_job;
231			}
232			} else {
233			# for some reason, connected-oriented transports seem to need this
234	root	1.5	delete $TRANSPORT[$fileno]
235			unless --$TRANSPORT[$fileno][0];
236	root	1.3	}
237	root	1.1
238	root	1.3	$msg->error;
239			return;
240	root	1.1	}
241
242	root	1.3	# For connection-oriented Transport Domains, it is possible to
243			# "recv" an empty buffer if reassembly is required.
244			if (!$msg->length) {
245			return;
246			}
247	root	1.1
248	root	1.3	# Hand the message over to Message Processing.
249			if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
250			$MESSAGE_PROCESSING->error;
251			return;
252			}
253	root	1.1
254	root	1.3	# Set the error if applicable.
255			$msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;
256	root	1.1
257	root	1.3	# Notify the command generator to process the response.
258			$msg->process_response_pdu;
259	root	1.1
260	root	1.3	# Cancel the timeout.
261			my $rtimeout_w = $msg->timeout_id;
262			if ($$rtimeout_w) {
263			undef $$rtimeout_w;
264
265	root	1.9	--$BUSY;
266	root	1.3	kick_job;
267
268	root	1.5	unless (--$TRANSPORT[$fileno][0]) {
269			delete $TRANSPORT[$fileno];
270	root	1.3	return;
271			}
272			}
273	root	1.1	}
274
275	root	1.4	# when we end up here, we successfully handled $MAX_RECVQUEUE
276			# replies in one iteration, so assume we are overloaded
277			# and reduce the amount of parallelity.
278	root	1.5	$MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.95) \|\| 1;
279	root	1.8	};
280	root	1.1	}
281
282			$msg->timeout_id (\(my $rtimeout_w =
283	root	1.8	AE::timer $pdu->timeout, 0, sub {
284	root	1.1	my $rtimeout_w = $msg->timeout_id;
285			if ($$rtimeout_w) {
286			undef $$rtimeout_w;
287	root	1.5	delete $TRANSPORT[$fileno]
288			unless --$TRANSPORT[$fileno][0];
289	root	1.1	}
290
291			if ($retries--) {
292			_send_pdu ($pdu, $retries);
293			} else {
294			$MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id);
295			$pdu->status_information ("No response from remote host '%s'", $pdu->hostname);
296	root	1.3
297	root	1.9	--$BUSY;
298	root	1.3	kick_job;
299	root	1.1	}
300			})
301	root	1.8	);
302	root	1.1	} else {
303	root	1.9	--$BUSY;
304	root	1.3	kick_job;
305	root	1.1	}
306			}
307
308	root	1.3	sub kick_job {
309			while ($BUSY < $MAX_OUTSTANDING) {
310			my $pdu = shift @QUEUE
311			or last;
312
313			++$BUSY;
314			_send_pdu $pdu, $pdu->retries;
315			}
316	root	1.8
317			$DONE and $DONE->() unless $BUSY;
318	root	1.3	}
319	root	1.6
320	root	1.1	sub send_pdu($$$) {
321			my (undef, $pdu, $delay) = @_;
322
323	root	1.3	# $delay is not very sensibly implemented by AnyEvent::SNMP,
324			# but apparently it is not a very sensible feature.
325	root	1.1	if ($delay > 0) {
326	root	1.3	++$BUSY;
327	root	1.8	my $delay_w; $delay_w = AE::timer $delay, 0, sub {
328	root	1.1	undef $delay_w;
329	root	1.3	push @QUEUE, $pdu;
330	root	1.9	--$BUSY;
331	root	1.3	kick_job;
332	root	1.8	};
333	root	1.1	return 1;
334			}
335
336	root	1.3	push @QUEUE, $pdu;
337			kick_job;
338
339	root	1.1	1
340			}
341
342			sub activate($) {
343	root	1.8	while ($BUSY) {
344			$DONE = AE::cv;
345			$DONE->recv;
346			undef $DONE;
347			}
348	root	1.1	}
349
350			sub one_event($) {
351	root	1.9	# should not ever be used
352	root	1.8	AnyEvent->one_event; #d# todo
353	root	1.1	}
354
355	root	1.6	sub set_max_outstanding($) {
356			$MAX_OUTSTANDING = $_[0];
357			kick_job;
358			}
359
360	root	1.1	=head1 SEE ALSO
361
362	root	1.3	L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.
363	root	1.1
364			=head1 AUTHOR
365
366			Marc Lehmann <schmorp@schmorp.de>
367			http://home.schmorp.de/
368
369			=cut
370
371			1
372