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Comparing cvsroot/AnyEvent-SNMP/README (file contents):
Revision 1.1 by root, Mon Dec 3 17:27:38 2007 UTC vs.
Revision 1.7 by root, Wed Oct 9 18:22:59 2019 UTC

1NAME 1NAME
2 Net::SNMP::EV - adaptor to integrate Net::SNMP into the EV event loop. 2 AnyEvent::SNMP - adaptor to integrate Net::SNMP into AnyEvent.
3 3
4SYNOPSIS 4SYNOPSIS
5 use EV; 5 use AnyEvent::SNMP;
6 use Net::SNMP; 6 use Net::SNMP;
7 use Net::SNMP::EV;
8 7
9 # just use Net::SNMP and EV as you like: 8 # just use Net::SNMP and AnyEvent as you like:
10 9
11 ... start non-blocking snmp request(s)... 10 # use a condvar to transfer results, this is
11 # just an example, you can use a naked callback as well.
12 my $cv = AnyEvent->condvar;
12 13
13 EV::loop; 14 # ... start non-blocking snmp request(s)...
15 Net::SNMP->session (-hostname => "127.0.0.1",
16 -community => "public",
17 -nonblocking => 1)
18 ->get_request (-callback => sub { $cv->send (@_) });
19
20 # ... do something else until the result is required
21 my @result = $cv->wait;
14 22
15DESCRIPTION 23DESCRIPTION
16 This module coerces the Net::SNMP scheduler to use the EV high 24 This module implements an alternative "event dispatcher" for Net::SNMP,
17 performance event loop as underlying event loop, i.e. EV will be used by 25 using AnyEvent as a backend. This integrates Net::SNMP into AnyEvent.
18 Net::SNMP for all events. 26 That means you can make non-blocking Net::SNMP calls and as long as
27 other parts of your program also use AnyEvent (or some event loop
28 supported by AnyEvent), they will run in parallel.
19 29
20 This integrates Net::SNMP into EV: You can make non-blocking Net::SNMP 30 Also, the Net::SNMP scheduler is very inefficient with respect to both
21 calls and as long as your main program uses the EV event loop, they will 31 CPU and memory usage. Most AnyEvent backends (including the pure-perl
22 run in parallel to anything else that uses EV or AnyEvent. 32 backend) fare much better than the Net::SNMP dispatcher.
33
34 Another major added feature 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
40 A potential disadvantage of this module is that replacing the dispatcher
41 is not at all a documented thing to do, so future changes in Net::SNMP
42 might break this module (or the many similar ones).
23 43
24 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
25 anything special apart from loading it. 45 anything special apart from loading it *before doing any non-blocking
46 requests with Net::SNMP*. It is recommended but not required to load
47 this module before "Net::SNMP".
26 48
27 The module is quite short, you cna use it to do a similar integration 49GLOBAL VARIABLES
28 into e.g. Event or other event loops. 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.
29 54
30BUGS 55 Net::SNMP is very fast at creating and sending SNMP requests, but
31 Net::SNMP has no (documented or otherwise) API to do what this module 56 much slower at parsing (big, bulk) responses. This makes it easy to
32 does. As such, this module rummages around in the internals of Net::SNMP 57 request a lot of data that can take many seconds to parse.
33 in a rather inacceptable way, and as thus might be very sensitive to the 58
34 version of Net::SNMP used (it has been tested with some 5.x versions 59 In the best case, this can lead to unnecessary delays (and even
35 only, YMMV). 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 noticeable 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 parallelity, 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 maximum, usually.
99
100 This algorithm works reasonably well as long as the responses,
101 response latencies and processing times are the same per packet on
102 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;
36 123
37SEE ALSO 124SEE ALSO
38 EV, Net::SNMP, AnyEvent, Glib::EV. 125 AnyEvent, Net::SNMP, Net::SNMP::XS, Net::SNMP::EV.
39 126
40AUTHOR 127AUTHOR
41 Marc Lehmann <schmorp@schmorp.de> 128 Marc Lehmann <schmorp@schmorp.de>
42 http://home.schmorp.de/ 129 http://home.schmorp.de/
43 130

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