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Revision 1.1 by root, Tue Mar 31 21:55:18 2009 UTC vs.
Revision 1.11 by root, Sun Oct 31 18:26:27 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>.
47 51
52=head1 GLOBAL VARIABLES
53
54=over 4
55
56=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic)
57
58=item AnyEvent::SNMP::set_max_outstanding $new_value
59
60Use this package variable to restrict the number of outstanding SNMP
61requests at any point in time.
62
63Net::SNMP is very fast at creating and sending SNMP requests, but much
64slower at parsing (big, bulk) responses. This makes it easy to request a
65lot of data that can take many seconds to parse.
66
67In the best case, this can lead to unnecessary delays (and even time-outs,
68as the data has been received but not yet processed) and in the worst
69case, this can lead to packet loss, when the receive queue overflows and
70the kernel can no longer accept new packets.
71
72To avoid this, you can (and should) limit the number of outstanding
73requests to a number low enough so that parsing time doesn't introduce
74noticable delays.
75
76Unfortunately, this number depends not only on processing speed and load
77of the machine running Net::SNMP, but also on the network latency and the
78speed of your SNMP agents.
79
80AnyEvent::SNMP tries to dynamically adjust this number upwards and
81downwards.
82
83Increasing C<$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
93Note that you can use L<Net::SNMP::XS> to speed up parsing of responses
94considerably.
95
96=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<8>)
97
98=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>)
99
100These values specify the minimum and maximum receive queue length (in
101units of one response packet).
102
103When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per iteration
104it will reduce $MAX_OUTSTANDING. If it handles less than $MIN_RECVQUEUE,
105it increases $MAX_OUTSTANDING.
106
107This has the result of adjusting the number of outstanding requests so that
108the recv queue is between the minimum and maximu, usually.
109
110This algorithm works reasonably well as long as the responses, response
111latencies and processing times are the same size per packet on average.
112
113=back
114
115=head1 COMPATIBILITY
116
117This module may be used as a drop in replacement for the
118Net::SNMP::Dispatcher in existing programs. You can still call
119C<snmp_dispatcher> to start the event-loop, but then you loose the benefit
120of 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
48=cut 136=cut
49 137
50package AnyEvent::SNMP; 138package AnyEvent::SNMP;
51 139
52no warnings; 140use common::sense;
53use strict qw(subs vars);
54 141
55# it is possible to do this without loading 142# it is possible to do this without loading
56# Net::SNMP::Dispatcher, but much more awkward. 143# Net::SNMP::Dispatcher, but much more awkward.
57use Net::SNMP::Dispatcher; 144use Net::SNMP::Dispatcher;
58 145
… …
61} 148}
62 149
63use Net::SNMP (); 150use Net::SNMP ();
64use AnyEvent (); 151use AnyEvent ();
65 152
66our $VERSION = '0.1'; 153our $VERSION = '1.0';
67 154
68$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher; 155$Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher;
69 156
70our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING; 157our $MESSAGE_PROCESSING = $Net::SNMP::Dispatcher::MESSAGE_PROCESSING;
71 158
72# avoid the method call
73my $timer = sub { shift->timer (@_) };
74AnyEvent::post_detect { $timer = AnyEvent->can ("timer") };
75
76our $BUSY; 159our $BUSY;
160our $DONE; # finished all jobs
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
… …
97 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id) 188 $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id)
98 if $pdu->expect_response; 189 if $pdu->expect_response;
99 190
100 # A crude attempt to recover from temporary failures. 191 # A crude attempt to recover from temporary failures.
101 if ($retries-- > 0 && ($!{EAGAIN} || $!{EWOULDBLOCK} || $!{ENOSPC})) { 192 if ($retries-- > 0 && ($!{EAGAIN} || $!{EWOULDBLOCK} || $!{ENOSPC})) {
102 my $retry_w; $retry_w = AnyEvent->$timer (after => $pdu->timeout, cb => sub { 193 my $retry_w; $retry_w = AE::timer $pdu->timeout, 0, sub {
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] = AE::io $transport->socket, 0, 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 } 279 };
280 }
140 281
141 # For connection-oriented Transport Domains, it is possible to 282 $msg->timeout_id (\(my $rtimeout_w =
142 # "recv" an empty buffer if reassembly is required. 283 AE::timer $pdu->timeout, 0, sub {
143 if (!$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; 284 my $rtimeout_w = $msg->timeout_id;
158 if ($$rtimeout_w) { 285 if ($$rtimeout_w) {
159 undef $$rtimeout_w; 286 undef $$rtimeout_w;
160 delete $TRANSPORT{$transport+0} 287 delete $TRANSPORT[$fileno]
161 unless --$TRANSPORT{$transport+0}[0]; 288 unless --$TRANSPORT[$fileno][0];
162
163 --$BUSY;
164 }
165
166 # Notify the command generator to process the response.
167 $msg->process_response_pdu;
168 });
169 }
170
171 #####d# timeout_id, wtf?
172 $msg->timeout_id (\(my $rtimeout_w =
173 AnyEvent->$timer (after => $pdu->timeout, cb => sub {
174 my $rtimeout_w = $msg->timeout_id;
175 if ($$rtimeout_w) {
176 undef $$rtimeout_w;
177 delete $TRANSPORT{$transport+0}
178 unless --$TRANSPORT{$transport+0}[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;
192 } 305 }
306}
307
308sub 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
317 $DONE and $DONE->() unless $BUSY;
193} 318}
194 319
195sub send_pdu($$$) { 320sub send_pdu($$$) {
196 my (undef, $pdu, $delay) = @_; 321 my (undef, $pdu, $delay) = @_;
197 322
198 ++$BUSY; 323 # $delay is not very sensibly implemented by AnyEvent::SNMP,
199 324 # but apparently it is not a very sensible feature.
200 if ($delay > 0) { 325 if ($delay > 0) {
326 ++$BUSY;
201 my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub { 327 my $delay_w; $delay_w = AE::timer $delay, 0, sub {
202 undef $delay_w; 328 undef $delay_w;
203 _send_pdu ($pdu, $pdu->retries); 329 push @QUEUE, $pdu;
330 --$BUSY;
331 kick_job;
204 }); 332 };
205 return 1; 333 return 1;
206 } 334 }
207 335
208 _send_pdu $pdu, $pdu->retries; 336 push @QUEUE, $pdu;
337 kick_job;
338
209 1 339 1
210} 340}
211 341
212sub activate($) { 342sub activate($) {
213 AnyEvent->one_event while $BUSY; 343 while ($BUSY) {
344 $DONE = AE::cv;
345 $DONE->recv;
346 undef $DONE;
347 }
214} 348}
215 349
216sub one_event($) { 350sub one_event($) {
217 die; 351 # should not ever be used
352 AnyEvent->one_event; #d# todo
353}
354
355sub set_max_outstanding($) {
356 $MAX_OUTSTANDING = $_[0];
357 kick_job;
218} 358}
219 359
220=head1 SEE ALSO 360=head1 SEE ALSO
221 361
222L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::EV>. 362L<AnyEvent>, L<Net::SNMP>, L<Net::SNMP::XS>, L<Net::SNMP::EV>.
223 363
224=head1 AUTHOR 364=head1 AUTHOR
225 365
226 Marc Lehmann <schmorp@schmorp.de> 366 Marc Lehmann <schmorp@schmorp.de>
227 http://home.schmorp.de/ 367 http://home.schmorp.de/

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