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 ressources 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 programm 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 theadd_oid_entry()
andadd_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
Meta CPAN
RT: CPAN's request tracker
http://rt.cpan.org/Public/Dist/Display.html?Name=SNMP-Extension-PassPersist
AnnoCPAN: Annotated CPAN documentation
CPAN Ratings
AUTHOR
Sébastien Aperghis-Tramoni, <sebastien at aperghis.net>
COPYRIGHT & LICENSE
Copyright 2008-2011 Sébastien 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.