bionic (3) SNMP::Extension::PassPersist.3pm.gz
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.