ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/cvsroot/AnyEvent-SNMP/SNMP.pm
(Generate patch)

Comparing cvsroot/AnyEvent-SNMP/SNMP.pm (file contents):
Revision 1.1 by root, Tue Mar 31 21:55:18 2009 UTC vs.
Revision 1.7 by root, Sun Aug 2 14:24:23 2009 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent::SNMP - adaptor to integrate Net::SNMP into Anyevent. 3AnyEvent::SNMP - adaptor to integrate Net::SNMP into AnyEvent.
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use AnyEvent::SNMP; 7 use AnyEvent::SNMP;
8 use Net::SNMP; 8 use Net::SNMP;
… …
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
54=item AnyEvent::SNMP::set_max_outstanding $new_value
55
56Use this package variable to restrict the number of outstanding SNMP
57requests at any point in time.
58
59Net::SNMP is very fast at creating and sending SNMP requests, but much
60slower at parsing (big, bulk) responses. This makes it easy to request a
61lot of data that can take many seconds to parse.
62
63In the best case, this can lead to unnecessary delays (and even time-outs,
64as the data has been received but not yet processed) and in the worst
65case, this can lead to packet loss, when the receive queue overflows and
66the kernel can no longer accept new packets.
67
68To avoid this, you can (and should) limit the number of outstanding
69requests to a number low enough so that parsing time doesn't introduce
70noticable delays.
71
72Unfortunately, this number depends not only on processing speed and load
73of the machine running Net::SNMP, but also on the network latency and the
74speed of your SNMP agents.
75
76AnyEvent::SNMP tries to dynamically adjust this number dynamically upwards
77and downwards.
78
79Increasing C<$MAX_OUTSTANDING> will not automatically use the
80C<extra request slots. To increase $MAX_OUTSTANDING> and make
81C<C<AnyEvent::SNMP> make use of the extra paralellity, call
82C<AnyEvent::SNMP::set_max_outstanding> with the new value, e.g.:
83
84 AnyEvent::SNMP::set_max_outstanding 500;
85
86Although due to the dynamic adjustment, this might have little lasting
87effect.
88
89Note that you can use L<Net::SNMP::XS> to speed up parsing of responses
90considerably.
91
92=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<8>)
93
94=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>)
95
96These values specify the minimum and maximum receive queue length (in
97units of one response packet).
98
99When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per iteration
100it will reduce $MAX_OUTSTANDING. If it handles less than $MIN_RECVQUEUE,
101it increases $MAX_OUTSTANDING.
102
103This has the result of adjusting the number of outstanding requests so that
104the recv queue is between the minimum and maximu, usually.
105
106This algorithm works reasonably well as long as the responses, response
107latencies and processing times are the same size per packet on average.
108
109=back
110
111=head1 COMPATIBILITY
112
113This module may be used as a drop in replacement for the
114Net::SNMP::Dispatcher in existing programs. You can still call
115C<snmp_dispatcher> to start the event-loop, but then you loose the benefit
116of mixing Net::SNMP events with other events.
117
118 use AnyEvent::SNMP;
119 use Net::SNMP;
120
121 # just use Net::SNMP as before
122
123 # ... start non-blocking snmp request(s)...
124 Net::SNMP->session (
125 -hostname => "127.0.0.1",
126 -community => "public",
127 -nonblocking => 1,
128 )->get_request (-callback => sub { ... });
129
130 snmp_dispatcher;
131
48=cut 132=cut
49 133
50package AnyEvent::SNMP; 134package AnyEvent::SNMP;
51 135
52no warnings; 136no warnings;
… …
61} 145}
62 146
63use Net::SNMP (); 147use Net::SNMP ();
64use AnyEvent (); 148use AnyEvent ();
65 149
66our $VERSION = '0.1'; 150our $VERSION = '0.2';
67 151
68$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher; 152$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
69 153
70our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING; 154our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
71 155
72# avoid the method call 156# avoid the method call
73my $timer = sub { shift->timer (@_) }; 157my $timer = sub { shift->timer (@_) };
74AnyEvent::post_detect { $timer = AnyEvent->can ("timer") }; 158AnyEvent::post_detect { $timer = AnyEvent->can ("timer") };
75 159
76our $BUSY; 160our $BUSY;
77our %TRANSPORT; # address => [count, watcher] 161our @TRANSPORT; # fileno => [count, watcher]
162our @QUEUE;
163our $MAX_OUTSTANDING = 50;
164our $MIN_RECVQUEUE = 8;
165our $MAX_RECVQUEUE = 64;
166
167sub kick_job;
78 168
79sub _send_pdu { 169sub _send_pdu {
80 my ($pdu, $retries) = @_; 170 my ($pdu, $retries) = @_;
81 171
82 # mostly copied from Net::SNMP::Dispatch 172 # mostly copied from Net::SNMP::Dispatch
… …
85 # create the new outgoing message. 175 # create the new outgoing message.
86 my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu); 176 my $msg = $MESSAGE_PROCESSING->prepare_outgoing_msg ($pdu);
87 177
88 if (!defined $msg) { 178 if (!defined $msg) {
89 --$BUSY; 179 --$BUSY;
180 kick_job;
90 # Inform the command generator about the Message Processing error. 181 # Inform the command generator about the Message Processing error.
91 $pdu->status_information ($MESSAGE_PROCESSING->error); 182 $pdu->status_information ($MESSAGE_PROCESSING->error);
92 return; 183 return;
93 } 184 }
94 185
… …
103 undef $retry_w; 194 undef $retry_w;
104 _send_pdu ($pdu, $retries); 195 _send_pdu ($pdu, $retries);
105 }); 196 });
106 } else { 197 } else {
107 --$BUSY; 198 --$BUSY;
199 kick_job;
108 } 200 }
109 201
110 # Inform the command generator about the send() error. 202 # Inform the command generator about the send() error.
111 $pdu->status_information ($msg->error); 203 $pdu->status_information ($msg->error);
112 return; 204 return;
113 } 205 }
114 206
115 # Schedule the timeout handler if the message expects a response. 207 # Schedule the timeout handler if the message expects a response.
116 if ($pdu->expect_response) { 208 if ($pdu->expect_response) {
117 my $transport = $msg->transport; 209 my $transport = $msg->transport;
210 my $fileno = $transport->fileno;
118 211
119 # register the transport 212 # register the transport
120 unless ($TRANSPORT{$transport+0}[0]++) { 213 unless ($TRANSPORT[$fileno][0]++) {
121 $TRANSPORT{$transport+0}[1] = AnyEvent->io (fh => $transport->socket, poll => 'r', cb => sub { 214 $TRANSPORT[$fileno][1] = AnyEvent->io (fh => $transport->socket, poll => 'r', cb => sub {
215 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 216 # Create a new Message object to receive the response
123 my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport); 217 my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport);
124 218
125 if (!defined $msg) { 219 if (!defined $msg) {
126 die sprintf 'Failed to create Message object [%s]', $error; 220 die sprintf 'Failed to create Message object [%s]', $error;
221 }
222
223 # Read the message from the Transport Layer
224 if (!defined $msg->recv) {
225 if ($transport->connectionless) {
226 # if we handled very few replies and we have queued work, try
227 # to increase the parallelity as we probably can handle more.
228 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 delete $TRANSPORT[$fileno]
235 unless --$TRANSPORT[$fileno][0];
236 }
237
238 $msg->error;
239 return;
240 }
241
242 # For connection-oriented Transport Domains, it is possible to
243 # "recv" an empty buffer if reassembly is required.
244 if (!$msg->length) {
245 return;
246 }
247
248 # Hand the message over to Message Processing.
249 if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) {
250 $MESSAGE_PROCESSING->error;
251 return;
252 }
253
254 # Set the error if applicable.
255 $msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error;
256
257 # Notify the command generator to process the response.
258 $msg->process_response_pdu;
259
260 # Cancel the timeout.
261 my $rtimeout_w = $msg->timeout_id;
262 if ($$rtimeout_w) {
263 undef $$rtimeout_w;
264
265 --$BUSY;
266 kick_job;
267
268 unless (--$TRANSPORT[$fileno][0]) {
269 delete $TRANSPORT[$fileno];
270 return;
271 }
272 }
127 } 273 }
128 274
129 # Read the message from the Transport Layer 275 # when we end up here, we successfully handled $MAX_RECVQUEUE
130 if (!defined $msg->recv) { 276 # replies in one iteration, so assume we are overloaded
131 # for some reason, connected-oriented transports seem to need this 277 # and reduce the amount of parallelity.
132 unless ($transport->connectionless) { 278 $MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.95) || 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 }); 279 });
169 } 280 }
170 281
171 #####d# timeout_id, wtf?
172 $msg->timeout_id (\(my $rtimeout_w = 282 $msg->timeout_id (\(my $rtimeout_w =
173 AnyEvent->$timer (after => $pdu->timeout, cb => sub { 283 AnyEvent->$timer (after => $pdu->timeout, cb => sub {
174 my $rtimeout_w = $msg->timeout_id; 284 my $rtimeout_w = $msg->timeout_id;
175 if ($$rtimeout_w) { 285 if ($$rtimeout_w) {
176 undef $$rtimeout_w; 286 undef $$rtimeout_w;
177 delete $TRANSPORT{$transport+0} 287 delete $TRANSPORT[$fileno]
178 unless --$TRANSPORT{$transport+0}[0]; 288 unless --$TRANSPORT[$fileno][0];
179 } 289 }
180 290
181 if ($retries--) { 291 if ($retries--) {
182 _send_pdu ($pdu, $retries); 292 _send_pdu ($pdu, $retries);
183 } else { 293 } else {
184 --$BUSY;
185 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id); 294 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id);
186 $pdu->status_information ("No response from remote host '%s'", $pdu->hostname); 295 $pdu->status_information ("No response from remote host '%s'", $pdu->hostname);
296
297 --$BUSY;
298 kick_job;
187 } 299 }
188 }) 300 })
189 )); 301 ));
190 } else { 302 } else {
191 --$BUSY; 303 --$BUSY;
304 kick_job;
305 }
306}
307
308sub kick_job {
309 while ($BUSY < $MAX_OUTSTANDING) {
310 my $pdu = shift @QUEUE
311 or last;
312
313 ++$BUSY;
314
315 _send_pdu $pdu, $pdu->retries;
192 } 316 }
193} 317}
194 318
195sub send_pdu($$$) { 319sub send_pdu($$$) {
196 my (undef, $pdu, $delay) = @_; 320 my (undef, $pdu, $delay) = @_;
197 321
198 ++$BUSY; 322 # $delay is not very sensibly implemented by AnyEvent::SNMP,
199 323 # but apparently it is not a very sensible feature.
200 if ($delay > 0) { 324 if ($delay > 0) {
325 ++$BUSY;
201 my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub { 326 my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub {
202 undef $delay_w; 327 undef $delay_w;
203 _send_pdu ($pdu, $pdu->retries); 328 --$BUSY;
329 push @QUEUE, $pdu;
330 kick_job;
204 }); 331 });
205 return 1; 332 return 1;
206 } 333 }
207 334
208 _send_pdu $pdu, $pdu->retries; 335 push @QUEUE, $pdu;
336 kick_job;
337
209 1 338 1
210} 339}
211 340
212sub activate($) { 341sub activate($) {
213 AnyEvent->one_event while $BUSY; 342 AnyEvent->one_event while $BUSY;
214} 343}
215 344
216sub one_event($) { 345sub one_event($) {
217 die; 346 AnyEvent->one_event;
347}
348
349sub set_max_outstanding($) {
350 $MAX_OUTSTANDING = $_[0];
351 kick_job;
218} 352}
219 353
220=head1 SEE ALSO 354=head1 SEE ALSO
221 355
222L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::EV>. 356L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.
223 357
224=head1 AUTHOR 358=head1 AUTHOR
225 359
226 Marc Lehmann <schmorp@schmorp.de> 360 Marc Lehmann <schmorp@schmorp.de>
227 http://home.schmorp.de/ 361 http://home.schmorp.de/

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines