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Revision 1.4 by root, Sun Apr 19 11:06:21 2009 UTC vs.
Revision 1.10 by root, Sun Oct 31 18:15:22 2010 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;
… …
23 my @result = $cv->wait; 23 my @result = $cv->wait;
24 24
25=head1 DESCRIPTION 25=head1 DESCRIPTION
26 26
27This module implements an alternative "event dispatcher" for Net::SNMP, 27This module implements an alternative "event dispatcher" for Net::SNMP,
28using AnyEvent as a backend. 28using AnyEvent as a backend. This integrates Net::SNMP into AnyEvent. That
29 29means you can make non-blocking Net::SNMP calls and as long as other
30This integrates Net::SNMP into AnyEvent: You can make non-blocking 30parts of your program also use AnyEvent (or some event loop supported by
31Net::SNMP calls and as long as other parts of your program also use 31AnyEvent), they will run in parallel.
32AnyEvent (or some event loop supported by AnyEvent), they will run in
33parallel.
34 32
35Also, the Net::SNMP scheduler is very inefficient with respect to both CPU 33Also, the Net::SNMP scheduler is very inefficient with respect to both CPU
36and memory usage. Most AnyEvent backends (including the pure-perl backend) 34and memory usage. Most AnyEvent backends (including the pure-perl backend)
37fare much better than the Net::SNMP dispatcher. 35fare much better than the Net::SNMP dispatcher.
38 36
37Another major added fetaure of this module over Net::SNMP is automatic
38rate-adjustments: Net::SNMP is so slow that firing a few thousand
39requests can cause many timeouts simply because Net::SNMP cannot process
40the replies in time. This module automatically adapts the send rate to
41avoid false timeouts caused by slow reply processing.
42
39A potential disadvantage is that replacing the dispatcher is not at all 43A potential disadvantage of this module is that replacing the dispatcher
40a documented thing to do, so future changes in Net::SNP might break this 44is not at all a documented thing to do, so future changes in Net::SNP
41module (or the many similar ones). 45might break this module (or the many similar ones).
42 46
43This module does not export anything and does not require you to do 47This module does not export anything and does not require you to do
44anything special apart from loading it I<before doing any non-blocking 48anything special apart from loading it I<before doing any non-blocking
45requests with Net::SNMP>. It is recommended but not required to load this 49requests with Net::SNMP>. It is recommended but not required to load this
46module before C<Net::SNMP>. 50module before C<Net::SNMP>.
… …
49 53
50=over 4 54=over 4
51 55
52=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic) 56=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic)
53 57
58=item AnyEvent::SNMP::set_max_outstanding $new_value
59
54Use this package variable to restrict the number of outstanding SNMP 60Use this package variable to restrict the number of outstanding SNMP
55requests at any point in time. 61requests at any point in time.
56 62
57Net::SNMP is very fast at creating and sending SNMP requests, but much 63Net::SNMP is very fast at creating and sending SNMP requests, but much
58slower at parsing (big, bulk) responses. This makes it easy to request a 64slower at parsing (big, bulk) responses. This makes it easy to request a
… …
61In the best case, this can lead to unnecessary delays (and even time-outs, 67In the best case, this can lead to unnecessary delays (and even time-outs,
62as the data has been received but not yet processed) and in the worst 68as the data has been received but not yet processed) and in the worst
63case, this can lead to packet loss, when the receive queue overflows and 69case, this can lead to packet loss, when the receive queue overflows and
64the kernel can no longer accept new packets. 70the kernel can no longer accept new packets.
65 71
66To avoid this, you can (and should) limit the number of outstanding requests 72To avoid this, you can (and should) limit the number of outstanding
67to a number low enough so that parsing time doesn't introduce noticable delays. 73requests to a number low enough so that parsing time doesn't introduce
74noticable delays.
68 75
69Unfortunately, this number depends not only on processing speed and load 76Unfortunately, this number depends not only on processing speed and load
70of the machine running Net::SNMP, but also on the network latency and the 77of the machine running Net::SNMP, but also on the network latency and the
71speed of your SNMP agents. 78speed of your SNMP agents.
72 79
73AnyEvent::SNMP tries to dynamically adjust this number dynamically upwards 80AnyEvent::SNMP tries to dynamically adjust this number dynamically upwards
74and downwards. 81and downwards.
75 82
83Increasing C<$MAX_OUTSTANDING> will not automatically use the
84extra request slots. To increase C<$MAX_OUTSTANDING> and make
85C<AnyEvent::SNMP> make use of the extra paralellity, call
86C<AnyEvent::SNMP::set_max_outstanding> with the new value, e.g.:
87
88 AnyEvent::SNMP::set_max_outstanding 500;
89
90Although due to the dynamic adjustment, this might have little lasting
91effect.
92
76Note that you can use L<Net::SNMP::XS> to speed up parsing of responses 93Note that you can use L<Net::SNMP::XS> to speed up parsing of responses
77considerably. 94considerably.
78 95
79=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<4>) 96=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<8>)
80 97
81=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>) 98=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>)
82 99
83These values specify the minimum and maximum receive queue length (in 100These values specify the minimum and maximum receive queue length (in
84units of one response packet). 101units of one response packet).
… …
132} 149}
133 150
134use Net::SNMP (); 151use Net::SNMP ();
135use AnyEvent (); 152use AnyEvent ();
136 153
137our $VERSION = '0.2'; 154our $VERSION = '1.0';
138 155
139$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher; 156$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
140 157
141our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING; 158our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
142 159
143# avoid the method call
144my $timer = sub { shift->timer (@_) };
145AnyEvent::post_detect { $timer = AnyEvent->can ("timer") };
146
147our $BUSY; 160our $BUSY;
161our $DONE; # finished all jobs
148our %TRANSPORT; # address => [count, watcher] 162our @TRANSPORT; # fileno => [count, watcher]
149our @QUEUE; 163our @QUEUE;
150our $MAX_OUTSTANDING = 50; 164our $MAX_OUTSTANDING = 50;
151our $MIN_RECVQUEUE = 4; 165our $MIN_RECVQUEUE = 8;
152our $MAX_RECVQUEUE = 64; 166our $MAX_RECVQUEUE = 64;
153 167
154sub kick_job; 168sub kick_job;
155 169
156sub _send_pdu { 170sub _send_pdu {
… …
175 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id) 189 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id)
176 if $pdu->expect_response; 190 if $pdu->expect_response;
177 191
178 # A crude attempt to recover from temporary failures. 192 # A crude attempt to recover from temporary failures.
179 if ($retries-- > 0 && ($!{EAGAIN} || $!{EWOULDBLOCK} || $!{ENOSPC})) { 193 if ($retries-- > 0 && ($!{EAGAIN} || $!{EWOULDBLOCK} || $!{ENOSPC})) {
180 my $retry_w; $retry_w = AnyEvent->$timer (after => $pdu->timeout, cb => sub { 194 my $retry_w; $retry_w = AE::timer $pdu->timeout, 0, sub {
181 undef $retry_w; 195 undef $retry_w;
182 _send_pdu ($pdu, $retries); 196 _send_pdu ($pdu, $retries);
183 }); 197 };
184 } else { 198 } else {
185 --$BUSY; 199 --$BUSY;
186 kick_job; 200 kick_job;
187 } 201 }
188 202
… …
192 } 206 }
193 207
194 # Schedule the timeout handler if the message expects a response. 208 # Schedule the timeout handler if the message expects a response.
195 if ($pdu->expect_response) { 209 if ($pdu->expect_response) {
196 my $transport = $msg->transport; 210 my $transport = $msg->transport;
211 my $fileno = $transport->fileno;
197 212
198 # register the transport 213 # register the transport
199 unless ($TRANSPORT{$transport+0}[0]++) { 214 unless ($TRANSPORT[$fileno][0]++) {
200 $TRANSPORT{$transport+0}[1] = AnyEvent->io (fh => $transport->socket, poll => 'r', cb => sub { 215 $TRANSPORT[$fileno][1] = AE::io $transport->socket, 0, sub {
201 for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go 216 for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go
202 # Create a new Message object to receive the response 217 # Create a new Message object to receive the response
203 my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport); 218 my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport);
204 219
205 if (!defined $msg) { 220 if (!defined $msg) {
… …
215 ++$MAX_OUTSTANDING; 230 ++$MAX_OUTSTANDING;
216 kick_job; 231 kick_job;
217 } 232 }
218 } else { 233 } else {
219 # for some reason, connected-oriented transports seem to need this 234 # for some reason, connected-oriented transports seem to need this
220 delete $TRANSPORT{$transport+0} 235 delete $TRANSPORT[$fileno]
221 unless --$TRANSPORT{$transport+0}[0]; 236 unless --$TRANSPORT[$fileno][0];
222 } 237 }
223 238
224 $msg->error; 239 $msg->error;
225 return; 240 return;
226 } 241 }
… …
249 undef $$rtimeout_w; 264 undef $$rtimeout_w;
250 265
251 --$BUSY; 266 --$BUSY;
252 kick_job; 267 kick_job;
253 268
254 unless (--$TRANSPORT{$transport+0}[0]) { 269 unless (--$TRANSPORT[$fileno][0]) {
255 delete $TRANSPORT{$transport+0}; 270 delete $TRANSPORT[$fileno];
256 return; 271 return;
257 } 272 }
258 } 273 }
259 } 274 }
260 275
261 # when we end up here, we successfully handled $MAX_RECVQUEUE 276 # when we end up here, we successfully handled $MAX_RECVQUEUE
262 # replies in one iteration, so assume we are overloaded 277 # replies in one iteration, so assume we are overloaded
263 # and reduce the amount of parallelity. 278 # and reduce the amount of parallelity.
264 $MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.9) || 1; 279 $MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.95) || 1;
265 }); 280 };
266 } 281 }
267 282
268 $msg->timeout_id (\(my $rtimeout_w = 283 $msg->timeout_id (\(my $rtimeout_w =
269 AnyEvent->$timer (after => $pdu->timeout, cb => sub { 284 AE::timer $pdu->timeout, 0, sub {
270 my $rtimeout_w = $msg->timeout_id; 285 my $rtimeout_w = $msg->timeout_id;
271 if ($$rtimeout_w) { 286 if ($$rtimeout_w) {
272 undef $$rtimeout_w; 287 undef $$rtimeout_w;
273 delete $TRANSPORT{$transport+0} 288 delete $TRANSPORT[$fileno]
274 unless --$TRANSPORT{$transport+0}[0]; 289 unless --$TRANSPORT[$fileno][0];
275 } 290 }
276 291
277 if ($retries--) { 292 if ($retries--) {
278 _send_pdu ($pdu, $retries); 293 _send_pdu ($pdu, $retries);
279 } else { 294 } else {
… …
282 297
283 --$BUSY; 298 --$BUSY;
284 kick_job; 299 kick_job;
285 } 300 }
286 }) 301 })
287 )); 302 );
288 } else { 303 } else {
289 --$BUSY; 304 --$BUSY;
290 kick_job; 305 kick_job;
291 } 306 }
292} 307}
… …
295 while ($BUSY < $MAX_OUTSTANDING) { 310 while ($BUSY < $MAX_OUTSTANDING) {
296 my $pdu = shift @QUEUE 311 my $pdu = shift @QUEUE
297 or last; 312 or last;
298 313
299 ++$BUSY; 314 ++$BUSY;
300
301 _send_pdu $pdu, $pdu->retries; 315 _send_pdu $pdu, $pdu->retries;
302 } 316 }
317
318 $DONE and $DONE->() unless $BUSY;
303} 319}
320
304sub send_pdu($$$) { 321sub send_pdu($$$) {
305 my (undef, $pdu, $delay) = @_; 322 my (undef, $pdu, $delay) = @_;
306 323
307 # $delay is not very sensibly implemented by AnyEvent::SNMP, 324 # $delay is not very sensibly implemented by AnyEvent::SNMP,
308 # but apparently it is not a very sensible feature. 325 # but apparently it is not a very sensible feature.
309 if ($delay > 0) { 326 if ($delay > 0) {
310 ++$BUSY; 327 ++$BUSY;
311 my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub { 328 my $delay_w; $delay_w = AE::timer $delay, 0, sub {
312 undef $delay_w; 329 undef $delay_w;
330 push @QUEUE, $pdu;
313 --$BUSY; 331 --$BUSY;
314 push @QUEUE, $pdu;
315 kick_job; 332 kick_job;
316 }); 333 };
317 return 1; 334 return 1;
318 } 335 }
319 336
320 push @QUEUE, $pdu; 337 push @QUEUE, $pdu;
321 kick_job; 338 kick_job;
322 339
323 1 340 1
324} 341}
325 342
326sub activate($) { 343sub activate($) {
327 AnyEvent->one_event while $BUSY; 344 while ($BUSY) {
345 $DONE = AE::cv;
346 $DONE->recv;
347 undef $DONE;
348 }
328} 349}
329 350
330sub one_event($) { 351sub one_event($) {
352 # should not ever be used
331 AnyEvent->one_event; 353 AnyEvent->one_event; #d# todo
354}
355
356sub set_max_outstanding($) {
357 $MAX_OUTSTANDING = $_[0];
358 kick_job;
332} 359}
333 360
334=head1 SEE ALSO 361=head1 SEE ALSO
335 362
336L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>. 363L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.

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