#!/usr/bin/perl -w
# -*- perl -*-

=head1 NAME

postfix_mailstats - Plugin to monitor the number of mails delivered and
rejected by postfix, with support for journald logs

=head1 CONFIGURATION

Configuration parameters for /etc/munin/postfix_mailstats,
if you need to override the defaults below:

 [postfix_mailstats]
  env.logdir  - Which logfile to use
  env.logfile - What file to read in logdir
  env.use_journald - Set to 1 to use journald instead of a logfile
  env.journalctlargs

=head2 DEFAULT CONFIGURATION

 [postfix_mailstats]
  env.logdir  /var/log
  env.logfile mail.log
  env.use_journald 0
  env.journalctlargs _SYSTEMD_UNIT=postfix@-.service

=head1 AUTHOR

Original plugin contributed by Nicolai Langfeldt,
extended for journald support by Stephan Kleber with some help by ChatGPT.

Records show that the plugin was contributed by Nicolai Langfeldt in
2003.  Nicolai can't find anything in his email about this and expects
the plugin is based on the corresponding exim plugin - to which it now
bears no resemblance.

=head1 LICENSE

GPLv2

=head1 MAGIC MARKERS

=begin comment

These magic markers are used by munin-node-configure when installing
munin-node.

=end comment

 #%# family=auto
 #%# capabilities=autoconf

=cut

use strict;
use Munin::Plugin;

my $statefile = $ENV{'MUNIN_PLUGSTATE'} . "/munin-plugin-postfix_mailstats.state";
my $pos;
my $delivered = 0;
my %rejects = ();

my $LOGDIR      = $ENV{'logdir'}  || '/var/log';
my $LOGFILE     = $ENV{'logfile'} || 'mail.log';
my $USE_JOURNALD = $ENV{'use_journald'} || 0;
my $journalctlargs = $ENV{'journalctlargs'} // '_SYSTEMD_UNIT=postfix@-.service';

my $logfile = "$LOGDIR/$LOGFILE";

if ( $ARGV[0] and $ARGV[0] eq "autoconf" )
{
    if ($USE_JOURNALD) {
        # Check if journalctl command is available
        if (system("which journalctl > /dev/null 2>&1") == 0) {
            print "yes\n";
            exit 0;
        } else {
            print "no (journalctl not found)\n";
            exit 0;
        }
    } else {
        # Logfile handling
        if (-d $LOGDIR)
        {
            if (-f $logfile)
            {
                if (-r $logfile)
                {
                    print "yes\n";
                    exit 0;
                }
                else
                {
                    print "no (logfile '$logfile' not readable)\n";
                }
            }
            else
            {
                print "no (logfile '$logfile' not found)\n";
            }
        }
        else
        {
            print "no (could not find logdir '$LOGDIR')\n";
        }
    }

    exit 0;
}

if ($USE_JOURNALD) {
    if (!defined $pos)
    {
        # Initial run.
        $pos = 0;
    }

    # Parse logs from journald
    parseJournald();
} else {
    # Load statefile if it exists
    if ( -f $statefile)
    {
        open (IN, '<', $statefile) or die "Unable to open state-file: $!\n";
        if (<IN> =~ /^(\d+):(\d+)/)
        {
            ($pos, $delivered) = ($1, $2);
        }
        while (<IN>)
        {
            if (/^([0-9a-z.\-]+):(\d+)$/)
            {
                $rejects{$1} = $2;
            }
        }
        close IN;
    }
    
    # Logfile handling
    if (! -f $logfile)
    {
        print "delivered.value U\n";
        foreach my $reason (sort keys %rejects)
        {
            my $fieldname = clean_fieldname("r$reason");
            print "$fieldname.value U\n";
        }
        exit 0;
    }

    my $startsize = (stat $logfile)[7];

    if (!defined $pos)
    {
        # Initial run.
        $pos = $startsize;
    }

    parseLogfile($logfile, $pos, $startsize);
    $pos = $startsize;
    
    # Save statefile
    if(-l $statefile) {
        die("$statefile is a symbolic link, refusing to touch it.");
    }
    open (OUT, '>', $statefile) or die "Unable to open statefile: $!\n";
    print OUT "$pos:$delivered\n";
    foreach my $i (sort keys %rejects)
    {
        print OUT "$i:", $rejects{$i}, "\n";
    }
    close OUT;
}

if ( $ARGV[0] and $ARGV[0] eq "config" )
{
    print "graph_title Postfix message throughput\n";
    print "graph_args --base 1000 -l 0\n";
    print "graph_vlabel mails / \${graph_period}\n";
    print "graph_scale  no\n";
    print "graph_total  Total\n";
    print "graph_category mail\n";
    print "graph_period minute\n";
    print "delivered.label delivered\n";
    print "delivered.type DERIVE\n";
    print "delivered.draw AREA\n";
    print "delivered.min 0\n";
    foreach my $reason (sort keys %rejects)
    {
        my $fieldname = clean_fieldname("r$reason");
        print "$fieldname.label reject $reason\n";
        print "$fieldname.type DERIVE\n";
        print "$fieldname.draw STACK\n";
        print "$fieldname.min 0\n";
    }
    exit 0;
}

print "delivered.value $delivered\n";
foreach my $reason (sort keys %rejects)
{
    my $fieldname = clean_fieldname("r$reason");
    print "$fieldname.value ", $rejects{$reason}, "\n";
}

# Function to parse logs from a regular logfile
sub parseLogfile
{
    my ($fname, $start, $stop) = @_;
    open (LOGFILE, $fname)
        or die "Unable to open logfile $fname for reading: $!\n";
    seek (LOGFILE, $start, 0)
        or die "Unable to seek to $start in $fname: $!\n";

    while (tell (LOGFILE) < $stop)
    {
        my $line = <LOGFILE>;
        chomp ($line);

        if ($line =~ / to=.*, status=sent /)
        {
            $delivered++;
        }
        elsif ($line =~ /postfix\/smtpd.*proxy-reject: \S+ (\S+)/ ||
               $line =~ /postfix\/smtpd.*reject: \S+ \S+ \S+ (\S+)/ ||
               $line =~ /postfix\/cleanup.* reject: (\S+)/ ||
               $line =~ /postfix\/cleanup.* milter-reject: \S+ \S+ \S+ (\S+)/)
        {
            $rejects{$1}++;
        }
    }
    close(LOGFILE) or warn "Error closing $fname: $!\n";
}

# Function to parse logs from journald
sub parseJournald
{
    my $cmd;
    $cmd = "journalctl --no-pager --quiet --since=" . `date -dlast-sunday +%Y-%m-%d` . " $journalctlargs";
    open(my $journal, '-|', $cmd) 
        or die "Unable to read journald logs: $!\n";

    while (my $line = <$journal>) {
        chomp($line);

        if ($line =~ / to=.*, status=sent /)
        {
            $delivered++;
        }
        elsif ($line =~ /postfix\/smtpd.*proxy-reject: \S+ (\S+)/ ||
               $line =~ /postfix\/smtpd.*reject: \S+ \S+ \S+ (\S+)/ ||
               $line =~ /postfix\/postscreen.*reject: \S+ \S+ \S+ (\S+)/ ||
               $line =~ /postfix\/cleanup.* reject: (\S+)/ ||
               $line =~ /postfix\/cleanup.* milter-reject: \S+ \S+ \S+ (\S+)/)
        {
            $rejects{$1}++;
        }
    }
    close($journal) or warn "Error closing journald stream: $!\n";
}

# vim:syntax=perl