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 (4 years, 7 months ago) by root
Branch:	MAIN
CVS Tags:	rel-6_02, HEAD
Changes since 1.13:	+6 -2 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	1.13	Another major added feature of this module over Net::SNMP is automatic
38	root	1.10	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	root	1.13	is not at all a documented thing to do, so future changes in Net::SNMP
45	root	1.10	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 $new_value
59
60	root	1.3	Use this package variable to restrict the number of outstanding SNMP
61			requests at any point in time.
62
63			Net::SNMP is very fast at creating and sending SNMP requests, but much
64			slower at parsing (big, bulk) responses. This makes it easy to request a
65			lot of data that can take many seconds to parse.
66
67			In the best case, this can lead to unnecessary delays (and even time-outs,
68			as the data has been received but not yet processed) and in the worst
69			case, this can lead to packet loss, when the receive queue overflows and
70			the kernel can no longer accept new packets.
71
72	root	1.6	To avoid this, you can (and should) limit the number of outstanding
73			requests to a number low enough so that parsing time doesn't introduce
74	root	1.13	noticeable delays.
75	root	1.3
76			Unfortunately, this number depends not only on processing speed and load
77			of the machine running Net::SNMP, but also on the network latency and the
78			speed of your SNMP agents.
79
80	root	1.11	AnyEvent::SNMP tries to dynamically adjust this number upwards and
81			downwards.
82	root	1.3
83	root	1.6	Increasing C<$MAX_OUTSTANDING> will not automatically use the
84	root	1.8	extra request slots. To increase C<$MAX_OUTSTANDING> and make
85	root	1.13	C<AnyEvent::SNMP> make use of the extra parallelity, 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	root	1.13	the recv queue is between the minimum and maximum, usually.
109	root	1.3
110			This algorithm works reasonably well as long as the responses, response
111	root	1.13	latencies and processing times are the same per packet on average.
112	root	1.3
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	root	1.12	# 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	root	1.1	sub Net::SNMP::Dispatcher::instance {
151			AnyEvent::SNMP::
152			}
153
154			use Net::SNMP ();
155			use AnyEvent ();
156
157	root	1.14	our $VERSION = '6.02';
158	root	1.1
159			$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
160
161			our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
162
163			our $BUSY;
164	root	1.8	our $DONE; # finished all jobs
165	root	1.5	our @TRANSPORT; # fileno => [count, watcher]
166	root	1.3	our @QUEUE;
167			our $MAX_OUTSTANDING = 50;
168	root	1.5	our $MIN_RECVQUEUE = 8;
169	root	1.3	our $MAX_RECVQUEUE = 64;
170
171	root	1.9	sub kick_job;
172	root	1.1
173			sub _send_pdu {
174			my ($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 $msg) {
183	root	1.9	--$BUSY;
184	root	1.3	kick_job;
185	root	1.1	# 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	root	1.8	my $retry_w; $retry_w = AE::timer $pdu->timeout, 0, sub {
198	root	1.1	undef $retry_w;
199			_send_pdu ($pdu, $retries);
200	root	1.8	};
201	root	1.1	} else {
202	root	1.9	--$BUSY;
203	root	1.3	kick_job;
204	root	1.1	}
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	root	1.5	my $fileno = $transport->fileno;
215	root	1.1
216			# register the transport
217	root	1.5	unless ($TRANSPORT[$fileno][0]++) {
218	root	1.8	$TRANSPORT[$fileno][1] = AE::io $transport->socket, 0, sub {
219	root	1.3	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	root	1.1
227	root	1.3	# Read the message from the Transport Layer
228			if (!defined $msg->recv) {
229			if ($transport->connectionless) {
230	root	1.4	# if we handled very few replies and we have queued work, try
231			# to increase the parallelity as we probably can handle more.
232	root	1.3	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	root	1.5	delete $TRANSPORT[$fileno]
239			unless --$TRANSPORT[$fileno][0];
240	root	1.3	}
241	root	1.1
242	root	1.3	$msg->error;
243			return;
244	root	1.1	}
245
246	root	1.3	# For connection-oriented Transport Domains, it is possible to
247			# "recv" an empty buffer if reassembly is required.
248			if (!$msg->length) {
249			return;
250			}
251	root	1.1
252	root	1.3	# Hand the message over to Message Processing.
253			if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
254			$MESSAGE_PROCESSING->error;
255			return;
256			}
257	root	1.1
258	root	1.3	# Set the error if applicable.
259			$msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;
260	root	1.1
261	root	1.3	# Notify the command generator to process the response.
262	root	1.14	# 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	root	1.1
268	root	1.3	# Cancel the timeout.
269			my $rtimeout_w = $msg->timeout_id;
270			if ($$rtimeout_w) {
271			undef $$rtimeout_w;
272
273	root	1.9	--$BUSY;
274	root	1.3	kick_job;
275
276	root	1.5	unless (--$TRANSPORT[$fileno][0]) {
277			delete $TRANSPORT[$fileno];
278	root	1.3	return;
279			}
280			}
281	root	1.1	}
282
283	root	1.4	# 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	root	1.5	$MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.95) \|\| 1;
287	root	1.8	};
288	root	1.1	}
289
290			$msg->timeout_id (\(my $rtimeout_w =
291	root	1.8	AE::timer $pdu->timeout, 0, sub {
292	root	1.1	my $rtimeout_w = $msg->timeout_id;
293			if ($$rtimeout_w) {
294			undef $$rtimeout_w;
295	root	1.5	delete $TRANSPORT[$fileno]
296			unless --$TRANSPORT[$fileno][0];
297	root	1.1	}
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'", $pdu->hostname);
304	root	1.3
305	root	1.9	--$BUSY;
306	root	1.3	kick_job;
307	root	1.1	}
308			})
309	root	1.8	);
310	root	1.1	} else {
311	root	1.9	--$BUSY;
312	root	1.3	kick_job;
313	root	1.1	}
314			}
315
316	root	1.3	sub kick_job {
317			while ($BUSY < $MAX_OUTSTANDING) {
318			my $pdu = shift @QUEUE
319			or last;
320
321			++$BUSY;
322			_send_pdu $pdu, $pdu->retries;
323			}
324	root	1.8
325			$DONE and $DONE->() unless $BUSY;
326	root	1.3	}
327	root	1.6
328	root	1.1	sub send_pdu($$$) {
329			my (undef, $pdu, $delay) = @_;
330
331	root	1.3	# $delay is not very sensibly implemented by AnyEvent::SNMP,
332			# but apparently it is not a very sensible feature.
333	root	1.1	if ($delay > 0) {
334	root	1.3	++$BUSY;
335	root	1.8	my $delay_w; $delay_w = AE::timer $delay, 0, sub {
336	root	1.1	undef $delay_w;
337	root	1.3	push @QUEUE, $pdu;
338	root	1.9	--$BUSY;
339	root	1.3	kick_job;
340	root	1.8	};
341	root	1.1	return 1;
342			}
343
344	root	1.3	push @QUEUE, $pdu;
345			kick_job;
346
347	root	1.1	1
348			}
349
350	root	1.12	sub loop($) {
351	root	1.8	while ($BUSY) {
352			$DONE = AE::cv;
353			$DONE->recv;
354			undef $DONE;
355			}
356	root	1.1	}
357
358	root	1.12	*activate = \&loop; # 5.x compatibility?
359			*listen = \&loop; # 5.x compatibility?
360
361	root	1.1	sub one_event($) {
362	root	1.9	# should not ever be used
363	root	1.8	AnyEvent->one_event; #d# todo
364	root	1.1	}
365
366	root	1.6	sub set_max_outstanding($) {
367			$MAX_OUTSTANDING = $_[0];
368			kick_job;
369			}
370
371	root	1.12	# 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	root	1.1	=head1 SEE ALSO
381
382	root	1.3	L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.
383	root	1.1
384			=head1 AUTHOR
385
386			Marc Lehmann <schmorp@schmorp.de>
387			http://home.schmorp.de/
388
389			=cut
390
391			1
392