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Revision 1.2 by root, Tue Mar 31 22:39:40 2009 UTC vs.
Revision 1.6 by root, Sun Apr 15 11:02:07 2012 UTC

1NAME 1NAME
2 AnyEvent::SNMP - adaptor to integrate Net::SNMP into Anyevent. 2 AnyEvent::SNMP - adaptor to integrate Net::SNMP into AnyEvent.
3 3
4SYNOPSIS 4SYNOPSIS
5 use AnyEvent::SNMP; 5 use AnyEvent::SNMP;
6 use Net::SNMP; 6 use Net::SNMP;
7 7
… …
20 # ... do something else until the result is required 20 # ... do something else until the result is required
21 my @result = $cv->wait; 21 my @result = $cv->wait;
22 22
23DESCRIPTION 23DESCRIPTION
24 This module implements an alternative "event dispatcher" for Net::SNMP, 24 This module implements an alternative "event dispatcher" for Net::SNMP,
25 using AnyEvent as a backend. 25 using AnyEvent as a backend. This integrates Net::SNMP into AnyEvent.
26 26 That means you can make non-blocking Net::SNMP calls and as long as
27 This integrates Net::SNMP into AnyEvent: You can make non-blocking 27 other parts of your program also use AnyEvent (or some event loop
28 Net::SNMP calls and as long as other parts of your program also use 28 supported by AnyEvent), they will run in parallel.
29 AnyEvent (or some event loop supported by AnyEvent), they will run in
30 parallel.
31 29
32 Also, the Net::SNMP scheduler is very inefficient with respect to both 30 Also, the Net::SNMP scheduler is very inefficient with respect to both
33 CPU and memory usage. Most AnyEvent backends (including the pure-perl 31 CPU and memory usage. Most AnyEvent backends (including the pure-perl
34 backend) fare much better than the Net::SNMP dispatcher. 32 backend) fare much better than the Net::SNMP dispatcher.
35 33
34 Another major added fetaure of this module over Net::SNMP is automatic
35 rate-adjustments: Net::SNMP is so slow that firing a few thousand
36 requests can cause many timeouts simply because Net::SNMP cannot process
37 the replies in time. This module automatically adapts the send rate to
38 avoid false timeouts caused by slow reply processing.
39
36 A potential disadvantage is that replacing the dispatcher is not at all 40 A potential disadvantage of this module is that replacing the dispatcher
37 a documented thing to do, so future changes in Net::SNP might break this 41 is not at all a documented thing to do, so future changes in Net::SNP
38 module (or the many similar ones). 42 might break this module (or the many similar ones).
39 43
40 This module does not export anything and does not require you to do 44 This module does not export anything and does not require you to do
41 anything special apart from loading it *before doing any non-blocking 45 anything special apart from loading it *before doing any non-blocking
42 requests with Net::SNMP*. It is recommended but not required to load 46 requests with Net::SNMP*. It is recommended but not required to load
43 this module before "Net::SNMP". 47 this module before "Net::SNMP".
44 48
49GLOBAL VARIABLES
50 $AnyEvent::SNMP::MAX_OUTSTANDING (default: 50, dynamic)
51 AnyEvent::SNMP::set_max_outstanding $new_value
52 Use this package variable to restrict the number of outstanding SNMP
53 requests at any point in time.
54
55 Net::SNMP is very fast at creating and sending SNMP requests, but
56 much slower at parsing (big, bulk) responses. This makes it easy to
57 request a lot of data that can take many seconds to parse.
58
59 In the best case, this can lead to unnecessary delays (and even
60 time-outs, as the data has been received but not yet processed) and
61 in the worst case, this can lead to packet loss, when the receive
62 queue overflows and the kernel can no longer accept new packets.
63
64 To avoid this, you can (and should) limit the number of outstanding
65 requests to a number low enough so that parsing time doesn't
66 introduce noticable delays.
67
68 Unfortunately, this number depends not only on processing speed and
69 load of the machine running Net::SNMP, but also on the network
70 latency and the speed of your SNMP agents.
71
72 AnyEvent::SNMP tries to dynamically adjust this number upwards and
73 downwards.
74
75 Increasing $MAX_OUTSTANDING will not automatically use the extra
76 request slots. To increase $MAX_OUTSTANDING and make
77 "AnyEvent::SNMP" make use of the extra paralellity, call
78 "AnyEvent::SNMP::set_max_outstanding" with the new value, e.g.:
79
80 AnyEvent::SNMP::set_max_outstanding 500;
81
82 Although due to the dynamic adjustment, this might have little
83 lasting effect.
84
85 Note that you can use Net::SNMP::XS to speed up parsing of responses
86 considerably.
87
88 $AnyEvent::SNMP::MIN_RECVQUEUE (default: 8)
89 $AnyEvent::SNMP::MAX_RECVQUEUE (default: 64)
90 These values specify the minimum and maximum receive queue length
91 (in units of one response packet).
92
93 When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per
94 iteration it will reduce $MAX_OUTSTANDING. If it handles less than
95 $MIN_RECVQUEUE, it increases $MAX_OUTSTANDING.
96
97 This has the result of adjusting the number of outstanding requests
98 so that the recv queue is between the minimum and maximu, usually.
99
100 This algorithm works reasonably well as long as the responses,
101 response latencies and processing times are the same size per packet
102 on average.
103
104COMPATIBILITY
105 This module may be used as a drop in replacement for the
106 Net::SNMP::Dispatcher in existing programs. You can still call
107 "snmp_dispatcher" to start the event-loop, but then you loose the
108 benefit of mixing Net::SNMP events with other events.
109
110 use AnyEvent::SNMP;
111 use Net::SNMP;
112
113 # just use Net::SNMP as before
114
115 # ... start non-blocking snmp request(s)...
116 Net::SNMP->session (
117 -hostname => "127.0.0.1",
118 -community => "public",
119 -nonblocking => 1,
120 )->get_request (-callback => sub { ... });
121
122 snmp_dispatcher;
123
45SEE ALSO 124SEE ALSO
46 AnyEvent, Net::SNMP, Net::SNMP::EV. 125 AnyEvent, Net::SNMP, Net::SNMP::XS, Net::SNMP::EV.
47 126
48AUTHOR 127AUTHOR
49 Marc Lehmann <schmorp@schmorp.de> 128 Marc Lehmann <schmorp@schmorp.de>
50 http://home.schmorp.de/ 129 http://home.schmorp.de/
51 130

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