Provided by: libsnmp-extension-passpersist-perl_0.07-2_all 
NAME
SNMP::Extension::PassPersist - Generic pass/pass_persist extension framework for Net-SNMP
VERSION
This is the documentation of "SNMP::Extension::PassPersist" version 0.07
SYNOPSIS
Typical setup for a "pass" program:
use strict;
use SNMP::Extension::PassPersist;
# create the object
my $extsnmp = SNMP::Extension::PassPersist->new;
# add a few OID entries
$extsnmp->add_oid_entry($oid, $type, $value);
$extsnmp->add_oid_entry($oid, $type, $value);
# run the program
$extsnmp->run;
Typical setup for a "pass_persist" program:
use strict;
use SNMP::Extension::PassPersist;
my $extsnmp = SNMP::Extension::PassPersist->new(
backend_collect => \&update_tree
);
$extsnmp->run;
sub update_tree {
my ($self) = @_;
# add a serie of OID entries
$self->add_oid_entry($oid, $type, $value);
...
# or directly add a whole OID tree
$self->add_oid_tree(\%oid_tree);
}
DESCRIPTION
This module is a framework for writing Net-SNMP extensions using the "pass" or
"pass_persist" mechanisms.
When in "pass_persist" mode, it provides a mechanism to spare resources by quitting from
the main loop after a given number of idle cycles.
This module can use "Sort::Key::OID" when it is available, for sorting OIDs faster than
with the internal pure Perl function.
METHODS
new()
Creates a new object. Can be given any attributes as a hash or hashref. See "ATTRIBUTES"
for the list of available attributes.
Examples:
For a "pass" command, most attributes are useless:
my $extsnmp = SNMP::Extension::PassPersist->new;
For a "pass_persist" command, you'll usually want to at least set the "backend_collect"
callback:
my $extsnmp = SNMP::Extension::PassPersist->new(
backend_collect => \&update_tree,
idle_count => 10, # no more than 10 idle cycles
refresh => 10, # refresh every 10 sec
);
run()
This method does the following things:
• process the command line arguments in order to decide in which mode the program has to
be executed
• call the backend init callback
• call the backend collect callback a first time
Then, when in "pass" mode, the corresponding SNMP command is executed, its result is
printed on the output filehandle, and "run()" returns.
When in "pass_persist" mode, "run()" enters a loop, reading Net-SNMP queries on its input
filehandle, processing them, and printing result on its output filehandle. The backend
collect callback is called every "refresh" seconds. If no query is read from the input
after "idle_count" cycles, "run()" returns.
add_oid_entry(FUNC_OID, FUNC_TYPE, FUNC_VALUE)
Add an entry to the OID tree.
add_oid_tree(HASH)
Merge an OID tree to the main OID tree, using the same structure as the one of the OID
tree itself.
dump_oid_tree()
Print a complete listing of the OID tree on the output file handle.
ATTRIBUTES
This module's attributes are generated by "Class::Accessor", and can therefore be passed
as arguments to "new()" or called as object methods.
backend_collect
Set the code reference for the collect callback. See also "CALLBACKS".
backend_fork
When set to true, the backend callbacks will be executed in a separate process. Default
value is false.
backend_init
Set the code reference for the init callback. See also "CALLBACKS".
backend_pipe
Contains the pipe used to communicate with the backend child, when executed in a separate
process.
dispatch
Gives access to the internal dispatch table, stored as a hash with the following
structure:
dispatch => {
SNMP_CMD => { nargs => NUMBER_ARGS, code => CODEREF },
...
}
where the SNMP command is always in lowercase, "nargs" gives the number of arguments
expected by the command and "code" the callback reference.
You should not modify this table unless you really know what you're doing.
heap
Give access to the heap.
idle_count
Get/set the number of idle cycles before ending the run loop.
input
Get/set the input filehandle.
oid_tree
Gives access to the internal OID tree, stored as a hash with the following structure:
oid_tree => {
FUNC_OID => [ FUNC_TYPE, FUNC_VALUE ],
...
}
where "FUNC_OID" is the absolute OID of the SNMP function, "FUNC_TYPE" the function type
("integer", "counter", "gauge", etc), and "FUNC_VALUE" the function value.
You should not directly modify this hash but instead use the appropriate methods for
adding OID entries.
output
Get/set the output filehandle.
refresh
Get/set the refresh delay before calling the backend collect callback to update the OID
tree.
CALLBACKS
The callbacks are invoked with the corresponding object as first argument, as for a normal
method. A heap is available for storing user-defined data.
In the specific case of a program running in "pass_persist" mode with a forked backend,
the callbacks are only executed in the child process (the forked backend).
The currently implemented callbacks are:
• init
This callback is called once, before the first collect invocation and before the main
loop. It can be accessed and modified through the "backend_init" attribute.
• collect
This callback is called every "refresh" seconds so the user can update the OID tree
using the "add_oid_entry()" and "add_oid_tree()" methods.
Examples
For simple needs, only the collect callback needs to be defined:
my $extsnmp = SNMP::Extension::PassPersist->new(
backend_collect => \&update_tree,
);
sub update_tree {
my ($self) = @_;
# fetch the number of running processes
my $nb_proc = @{ Proc::ProcessTable->new->table };
$self->add_oid_entry(".1.3.6.1.4.1.32272.10", gauge", $nb_proc);
}
A more advanced example is when there is a need to connect to a database, in which case
both the init and collect callback need to be defined:
my $extsnmp = SNMP::Extension::PassPersist->new(
backend_init => \&connect_db,
backend_collect => \&update_tree,
);
sub connect_db {
my ($self) = @_;
my $heap = $self->heap;
# connect to a database
my $dbh = DBI->connect($dsn, $user, $password);
$heap->{dbh} = $dbh;
}
sub update_tree {
my ($self) = @_;
my $heap = $self->heap;
# fetch the number of records from a given table
my $dbh = $heap->{dbh};
my $sth = $dbh->prepare_cached("SELECT count(*) FROM whatever");
$sth->execute;
my ($count) = $sth->fetchrow_array;
$self->add_oid_entry(".1.3.6.1.4.1.32272.20", "gauge", $count);
}
SEE ALSO
SNMP::Persist is another pass_persist backend for writing Net-SNMP extensions, but relies
on threads.
The documentation of Net-SNMP, especially the part on how to configure a "pass" or
"pass_persist" extension:
• main site: <http://www.net-snmp.org/>
• configuring a pass or pass_persist extension:
<http://www.net-snmp.org/docs/man/snmpd.conf.html#lbBB>
BUGS
Please report any bugs or feature requests to "bug-snmp-extension-passpersist at
rt.cpan.org", or through the web interface at
<http://rt.cpan.org/Public/Dist/Display.html?Name=SNMP-Extension-PassPersist>. I will be
notified, and then you'll automatically be notified of progress on your bug as I make
changes.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc SNMP::Extension::PassPersist
You can also look for information at:
• Search CPAN
<http://search.cpan.org/dist/SNMP-Extension-PassPersist>
• Meta CPAN
<https://metacpan.org/release/SNMP-Extension-PassPersist>
• RT: CPAN's request tracker
<http://rt.cpan.org/Public/Dist/Display.html?Name=SNMP-Extension-PassPersist>
• AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/SNMP-Extension-PassPersist>
• CPAN Ratings
<http://cpanratings.perl.org/d/SNMP-Extension-PassPersist>
AUTHOR
Sebastien Aperghis-Tramoni, "<sebastien at aperghis.net>"
COPYRIGHT & LICENSE
Copyright 2008-2011 Sebastien Aperghis-Tramoni, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.