Read options from a config file or as the programm arguments, update POD

tools/munin2snmp/munin2snmp

@@ -1,24 +1,66 @@
 #!/usr/bin/perl
 
+use warnings;
 use strict;
 use NetSNMP::OID;
 use NetSNMP::ASN (':all');
 use NetSNMP::agent (':all');
 use IO::Socket;
+use Getopt::Long;
+use Pod::Usage;
 
 my %cache = ();         # Cache
 my @cache_oids = ();    # Keys, sorted
 my $cache_updated = 0;
-my $oidbase = ".1.3.6.1.4.1.123456.100.1.1";
 my $delimiter = ' = ';
+my $conf = '/etc/munin2snmp.conf';
+my %config;
+my $pidfile = '/var/run/munin2snmp.pid';
+
+my $usage = "Usage: $0 [options] \
+Options:
+--help                      : print help message\
+--host [host]               : munin-node host, default localhost\
+--port [port]               : munin-node port, default 4949\
+--base_oid [OID]            : base oid, default .1.3.6.1.4.1.123456.100.1.1\
+                              Don't forget to update MUNIN-MIB  OBJECT IDENTIFIER if you modify base_oid\
+--plugins  [load,cpu,..]    : comma separated list of munin-node plugins, default cpu,load,df\
+--pidfile  [file path]      : pidfile, default /var/run/munin2snmp.pid\
+";
+
+sub read_conf {
+    return if ( ! -e $conf );
+    open my $conf_fh,'<',$conf or die "Can't open the $conf, $!\n";
+    while (<$conf_fh>) {
+        chomp;
+        my ($param, $val) = split(/\s*=\s*/);
+        $config{"$param"} = $val;
+    }
+}
 
 # initialize
 my %Munin;
-$Munin{PORT} = '4949';
-$Munin{HOST} = 'localhost';
-
+if ( ! scalar @ARGV ) {
+    read_conf;
+}
+GetOptions (
+    "help"          => sub{pod2usage($usage)},
+    "host=s"        => \$config{munin_host},
+    "port=s"        => \$config{munin_port},
+    "base_oid=s"    => \$config{'base_oid'},
+    "plugins=s"     => \$config{'munin_plugins'},
+    "pidfile=s"     => \$pidfile,
+);
+$Munin{PORT} = $config{'munin_port'} || '4949';
+$Munin{HOST} = $config{'munin_host'} || 'localhost';
+my $oidbase  = $config{'base_oid'}   || '.1.3.6.1.4.1.123456.100.1.1';
 # See munin plugins dir for more plugins
-our @munin_plugins= qw ( load swap users uptime vmstat df );
+my @munin_plugins = qw (cpu load df);
+@munin_plugins = split(',',$config{'munin_plugins'}) if ( $config{'munin_plugins'});
+
+open my $pidfd,'>',$pidfile or die "Can't open $pidfile, $!\n";
+print $pidfd $$;
+close $pidfd;
 
 # Update cache
 sub update_stats {
@@ -59,7 +101,7 @@ sub handle_stats {
             if (exists $cache{$noid}) {
                 $request->setValue(ASN_OCTET_STR, "$cache{$noid}");
             }
-        } 
+        }
         elsif ($request_info->getMode() == MODE_GETNEXT) {
             # For a GETNEXT, we need to find a best match. This is the
             # first match strictly superior to the requested OID.
@@ -100,6 +142,7 @@ $agent->shutdown();
 sub shutdown {
     # Shutdown requested
     $running = 0;
+    unlink $pidfile if -e $pidfile;
 }
 
 #muninwalk
@@ -147,7 +190,7 @@ munin2snmp - SNMP Agent to query munin-node over snmp
 
 =head1 REQUIREMENTS
 
-Net::SNMP and IO::Socket perl modules, munin-node with some plugins
+Net::SNMP, Getopt::Long, Pod::Usage perl modules, munin-node with some plugins
 
 =head2 Example configuration
 
@@ -165,12 +208,28 @@ or another place where snmpd expects to find the MIB files.
 
 See also http://www.net-snmp.org/wiki/index.php/FAQ:MIBs_03
 
+It is possible to start munin2snmp as non-root user, for example
+run munin2snmp as Debian-snmp user on Debian Stretch:
+
+fix the /var/agentx permissions:
+
+  chmod  g+rx /var/agentx
+  chgrp Debian-snmp /var/agentx
+
+add to /etc/snmp/snmpd.conf: 
+
+  master          agentx
+  agentXperms 0640 0550 Debian-snmp Debian-snmp
+
+restart snmpd and start the agent as Debian-snmp:
+
+  su -l Debian-snmp -s /bin/bash -c "/tmp/munin2snmp.pl --pidfile /tmp/munin2snmp.pid --plugins iostat,vmstat"
 
 =head2 Usage
 
 After setting up snmpd, start the agent:
 
-  ./munin2snmp.pl
+  ./munin2snmp
 
 Now one can query the agent
 
@@ -179,6 +238,8 @@ Now one can query the agent
 where "1.3.6.1.4.1.123456.100.1.1" is example OID selected as the base
 tree for the agent.
 
+Change  OBJECT IDENTIFIER in the MUNIN-MIB file if you plan to use a different OID.
+
 You might need to change the host, port, oidbase and munin_plugins you want to use.
 
 The defaults:
@@ -186,7 +247,17 @@ The defaults:
   $Munin{PORT} = '4949';
   $Munin{HOST} = 'localhost'
   $oidbase = ".1.3.6.1.4.1.123456.100.1.1"
-  @munin_plugins = qw ( load swap users uptime vmstat df );
+  @munin_plugins = qw ( load cpu df );
+
+One can override the defaults by creating /etc/munin2snmp.conf file with the following
+configuration options:
+
+  munin_port    = [port]
+  munin_host    = [host]
+  base_oid      = [oid]
+  munin_plugins = [comma separated list of munin-node plugins]
+
+Or by specifying the parameters, see munin2snmp --help for the usage
 
 =head1 ACKNOWLEDGEMENTS
 
@@ -194,12 +265,20 @@ Heavily inspired by
 Vincent Bernat: https://github.com/vincentbernat/extend-netsnmp
 and Masahito Zembutsu: https://github.com/zembutsu/muninwalk
 
-=head1 AUTHOR
-
-Alex Mestiashvili <mailatgoogl@gmail.com>
- 
 =head1 LICENSE
 
-GPLv2
+ISC License (ISC)
 
+Copyright (c) 2016, Alex Mestiashvili <mailatgoogl@gmail.com>
 
+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.