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Comparing AnyEvent-SNMP/SNMP.pm (file contents):
Revision 1.1 by root, Tue Mar 31 21:55:18 2009 UTC vs.
Revision 1.4 by root, Sun Apr 19 11:06:21 2009 UTC

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43This module does not export anything and does not require you to do 43This module does not export anything and does not require you to do
44anything special apart from loading it I<before doing any non-blocking 44anything special apart from loading it I<before doing any non-blocking
45requests with Net::SNMP>. It is recommended but not required to load this 45requests with Net::SNMP>. It is recommended but not required to load this
46module before C<Net::SNMP>. 46module before C<Net::SNMP>.
47 47
48=head1 GLOBAL VARIABLES
49
50=over 4
51
52=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic)
53
54Use this package variable to restrict the number of outstanding SNMP
55requests at any point in time.
56
57Net::SNMP is very fast at creating and sending SNMP requests, but much
58slower at parsing (big, bulk) responses. This makes it easy to request a
59lot of data that can take many seconds to parse.
60
61In the best case, this can lead to unnecessary delays (and even time-outs,
62as the data has been received but not yet processed) and in the worst
63case, this can lead to packet loss, when the receive queue overflows and
64the kernel can no longer accept new packets.
65
66To avoid this, you can (and should) limit the number of outstanding requests
67to a number low enough so that parsing time doesn't introduce noticable delays.
68
69Unfortunately, this number depends not only on processing speed and load
70of the machine running Net::SNMP, but also on the network latency and the
71speed of your SNMP agents.
72
73AnyEvent::SNMP tries to dynamically adjust this number dynamically upwards
74and downwards.
75
76Note that you can use L<Net::SNMP::XS> to speed up parsing of responses
77considerably.
78
79=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<4>)
80
81=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>)
82
83These values specify the minimum and maximum receive queue length (in
84units of one response packet).
85
86When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per iteration
87it will reduce $MAX_OUTSTANDING. If it handles less than $MIN_RECVQUEUE,
88it increases $MAX_OUTSTANDING.
89
90This has the result of adjusting the number of outstanding requests so that
91the recv queue is between the minimum and maximu, usually.
92
93This algorithm works reasonably well as long as the responses, response
94latencies and processing times are the same size per packet on average.
95
96=back
97
98=head1 COMPATIBILITY
99
100This module may be used as a drop in replacement for the
101Net::SNMP::Dispatcher in existing programs. You can still call
102C<snmp_dispatcher> to start the event-loop, but then you loose the benefit
103of mixing Net::SNMP events with other events.
104
105 use AnyEvent::SNMP;
106 use Net::SNMP;
107
108 # just use Net::SNMP as before
109
110 # ... start non-blocking snmp request(s)...
111 Net::SNMP->session (
112 -hostname => "127.0.0.1",
113 -community => "public",
114 -nonblocking => 1,
115 )->get_request (-callback => sub { ... });
116
117 snmp_dispatcher;
118
48=cut 119=cut
49 120
50package AnyEvent::SNMP; 121package AnyEvent::SNMP;
51 122
52no warnings; 123no warnings;
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61} 132}
62 133
63use Net::SNMP (); 134use Net::SNMP ();
64use AnyEvent (); 135use AnyEvent ();
65 136
66our $VERSION = '0.1'; 137our $VERSION = '0.2';
67 138
68$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher; 139$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
69 140
70our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING; 141our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
71 142
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73my $timer = sub { shift->timer (@_) }; 144my $timer = sub { shift->timer (@_) };
74AnyEvent::post_detect { $timer = AnyEvent->can ("timer") }; 145AnyEvent::post_detect { $timer = AnyEvent->can ("timer") };
75 146
76our $BUSY; 147our $BUSY;
77our %TRANSPORT; # address => [count, watcher] 148our %TRANSPORT; # address => [count, watcher]
149our @QUEUE;
150our $MAX_OUTSTANDING = 50;
151our $MIN_RECVQUEUE = 4;
152our $MAX_RECVQUEUE = 64;
153
154sub kick_job;
78 155
79sub _send_pdu { 156sub _send_pdu {
80 my ($pdu, $retries) = @_; 157 my ($pdu, $retries) = @_;
81 158
82 # mostly copied from Net::SNMP::Dispatch 159 # mostly copied from Net::SNMP::Dispatch
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85 # create the new outgoing message. 162 # create the new outgoing message.
86 my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu); 163 my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu);
87 164
88 if (!defined $msg) { 165 if (!defined $msg) {
89 --$BUSY; 166 --$BUSY;
167 kick_job;
90 # Inform the command generator about the Message Processing error. 168 # Inform the command generator about the Message Processing error.
91 $pdu->status_information ($MESSAGE_PROCESSING->error); 169 $pdu->status_information ($MESSAGE_PROCESSING->error);
92 return; 170 return;
93 } 171 }
94 172
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103 undef $retry_w; 181 undef $retry_w;
104 _send_pdu ($pdu, $retries); 182 _send_pdu ($pdu, $retries);
105 }); 183 });
106 } else { 184 } else {
107 --$BUSY; 185 --$BUSY;
186 kick_job;
108 } 187 }
109 188
110 # Inform the command generator about the send() error. 189 # Inform the command generator about the send() error.
111 $pdu->status_information ($msg->error); 190 $pdu->status_information ($msg->error);
112 return; 191 return;
… …
117 my $transport = $msg->transport; 196 my $transport = $msg->transport;
118 197
119 # register the transport 198 # register the transport
120 unless ($TRANSPORT{$transport+0}[0]++) { 199 unless ($TRANSPORT{$transport+0}[0]++) {
121 $TRANSPORT{$transport+0}[1] = AnyEvent->io (fh => $transport->socket, poll => 'r', cb => sub { 200 $TRANSPORT{$transport+0}[1] = AnyEvent->io (fh => $transport->socket, poll => 'r', cb => sub {
201 for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go
122 # Create a new Message object to receive the response 202 # Create a new Message object to receive the response
123 my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport); 203 my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport);
124 204
125 if (!defined $msg) { 205 if (!defined $msg) {
126 die sprintf 'Failed to create Message object [%s]', $error; 206 die sprintf 'Failed to create Message object [%s]', $error;
207 }
208
209 # Read the message from the Transport Layer
210 if (!defined $msg->recv) {
211 if ($transport->connectionless) {
212 # if we handled very few replies and we have queued work, try
213 # to increase the parallelity as we probably can handle more.
214 if ($count < $MIN_RECVQUEUE && @QUEUE) {
215 ++$MAX_OUTSTANDING;
216 kick_job;
217 }
218 } else {
219 # for some reason, connected-oriented transports seem to need this
220 delete $TRANSPORT{$transport+0}
221 unless --$TRANSPORT{$transport+0}[0];
222 }
223
224 $msg->error;
225 return;
226 }
227
228 # For connection-oriented Transport Domains, it is possible to
229 # "recv" an empty buffer if reassembly is required.
230 if (!$msg->length) {
231 return;
232 }
233
234 # Hand the message over to Message Processing.
235 if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
236 $MESSAGE_PROCESSING->error;
237 return;
238 }
239
240 # Set the error if applicable.
241 $msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;
242
243 # Notify the command generator to process the response.
244 $msg->process_response_pdu;
245
246 # Cancel the timeout.
247 my $rtimeout_w = $msg->timeout_id;
248 if ($$rtimeout_w) {
249 undef $$rtimeout_w;
250
251 --$BUSY;
252 kick_job;
253
254 unless (--$TRANSPORT{$transport+0}[0]) {
255 delete $TRANSPORT{$transport+0};
256 return;
257 }
258 }
127 } 259 }
128 260
129 # Read the message from the Transport Layer 261 # when we end up here, we successfully handled $MAX_RECVQUEUE
130 if (!defined $msg->recv) { 262 # replies in one iteration, so assume we are overloaded
131 # for some reason, connected-oriented transports seem to need this 263 # and reduce the amount of parallelity.
132 unless ($transport->connectionless) { 264 $MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.9) || 1;
133 delete $TRANSPORT{$transport+0}
134 unless --$TRANSPORT{$transport+0}[0];
135 }
136
137 $msg->error;
138 return;
139 }
140
141 # For connection-oriented Transport Domains, it is possible to
142 # "recv" an empty buffer if reassembly is required.
143 if (!$msg->length) {
144 return;
145 }
146
147 # Hand the message over to Message Processing.
148 if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
149 $MESSAGE_PROCESSING->error;
150 return;
151 }
152
153 # Set the error if applicable.
154 $msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;
155
156 # Cancel the timeout.
157 my $rtimeout_w = $msg->timeout_id;
158 if ($$rtimeout_w) {
159 undef $$rtimeout_w;
160 delete $TRANSPORT{$transport+0}
161 unless --$TRANSPORT{$transport+0}[0];
162
163 --$BUSY;
164 }
165
166 # Notify the command generator to process the response.
167 $msg->process_response_pdu;
168 }); 265 });
169 } 266 }
170 267
171 #####d# timeout_id, wtf?
172 $msg->timeout_id (\(my $rtimeout_w = 268 $msg->timeout_id (\(my $rtimeout_w =
173 AnyEvent->$timer (after => $pdu->timeout, cb => sub { 269 AnyEvent->$timer (after => $pdu->timeout, cb => sub {
174 my $rtimeout_w = $msg->timeout_id; 270 my $rtimeout_w = $msg->timeout_id;
175 if ($$rtimeout_w) { 271 if ($$rtimeout_w) {
176 undef $$rtimeout_w; 272 undef $$rtimeout_w;
… …
179 } 275 }
180 276
181 if ($retries--) { 277 if ($retries--) {
182 _send_pdu ($pdu, $retries); 278 _send_pdu ($pdu, $retries);
183 } else { 279 } else {
184 --$BUSY;
185 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id); 280 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id);
186 $pdu->status_information ("No response from remote host '%s'", $pdu->hostname); 281 $pdu->status_information ("No response from remote host '%s'", $pdu->hostname);
282
283 --$BUSY;
284 kick_job;
187 } 285 }
188 }) 286 })
189 )); 287 ));
190 } else { 288 } else {
191 --$BUSY; 289 --$BUSY;
290 kick_job;
192 } 291 }
193} 292}
194 293
294sub kick_job {
295 while ($BUSY < $MAX_OUTSTANDING) {
296 my $pdu = shift @QUEUE
297 or last;
298
299 ++$BUSY;
300
301 _send_pdu $pdu, $pdu->retries;
302 }
303}
195sub send_pdu($$$) { 304sub send_pdu($$$) {
196 my (undef, $pdu, $delay) = @_; 305 my (undef, $pdu, $delay) = @_;
197 306
198 ++$BUSY; 307 # $delay is not very sensibly implemented by AnyEvent::SNMP,
199 308 # but apparently it is not a very sensible feature.
200 if ($delay > 0) { 309 if ($delay > 0) {
310 ++$BUSY;
201 my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub { 311 my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub {
202 undef $delay_w; 312 undef $delay_w;
203 _send_pdu ($pdu, $pdu->retries); 313 --$BUSY;
314 push @QUEUE, $pdu;
315 kick_job;
204 }); 316 });
205 return 1; 317 return 1;
206 } 318 }
207 319
208 _send_pdu $pdu, $pdu->retries; 320 push @QUEUE, $pdu;
321 kick_job;
322
209 1 323 1
210} 324}
211 325
212sub activate($) { 326sub activate($) {
213 AnyEvent->one_event while $BUSY; 327 AnyEvent->one_event while $BUSY;
214} 328}
215 329
216sub one_event($) { 330sub one_event($) {
217 die; 331 AnyEvent->one_event;
218} 332}
219 333
220=head1 SEE ALSO 334=head1 SEE ALSO
221 335
222L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::EV>. 336L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.
223 337
224=head1 AUTHOR 338=head1 AUTHOR
225 339
226 Marc Lehmann <schmorp@schmorp.de> 340 Marc Lehmann <schmorp@schmorp.de>
227 http://home.schmorp.de/ 341 http://home.schmorp.de/

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