#!/usr/bin/env perl
use 5.010;
use strict;
use warnings;
use autodie;
use Munin::Plugin;
use File::Temp qw(tempdir tempfile);
use Time::HiRes qw(gettimeofday tv_interval);
use File::Spec::Functions qw(catfile);
use File::Basename qw(basename);

=head1 NAME

munin_stats_plugins - Report the time it takes to run all munin plugins

=head1 SYNOPSIS

In F</etc/munin/plugin-conf.d/munin-node>, because we invoke plugins
with munin-run, some of which may need root privileges:

    [munin_stats_plugins]
    user root

Put this in cron somewhere:

    # Refresh the statistics
    MUNIN_STATS_PLUGINS_RELOAD=1 munin-run munin_stats_plugins

E.g.:

    40 4  * * * root MUNIN_STATS_PLUGINS_RELOAD=1 munin-run munin_stats_plugins

Then run it:

    # Get the statistics
    munin-run munin_stats_plugins

=head1 DESCRIPTION

Runs all the munin plugins in F</etc/munin/plugins> and reports the
time it takes to run each one with C<system> and L<Time::HiRes>. Since
running all the plugins again on each munin-update run would lead to
epic recursive failure, you have to reload the statistics database
yourself by reloading it in cron somewhere.

=head1 AUTHOR

Ævar Arnfjörð Bjarmason <avar@cpan.org>

=head1 LICENSE

This program is in the public domain.

=head1 MAGIC MARKERS

 #%# family=manual

=cut

my $statedir  = $ENV{MUNIN_PLUGSTATE};
my $statefile = $0; $statefile =~ s[^.*/][];
my $cache = catfile($statedir, $statefile . '-cache');
my $cache_tmp = "$cache.tmp";

my @plugins = parse_plugin_time($cache);

# We should reload our data
if (not $ARGV[0] and $ENV{MUNIN_STATS_PLUGINS_RELOAD}) {
    $ARGV[0] = 'reload';
}

given ($ARGV[0]) {
    when ("reload") {
        # Plugin names
        my @plugs = plugin_names();

        # Run all the plugins
        my $time = plugin_times(@plugs);

        write_plugin_times($cache_tmp, $cache, $time);
    }
    when ("config") {
        print <<END;
graph_title Munin plugin processing time
graph_scale yes
graph_vlabel seconds
graph_category munin
graph_info Shows the processing time of munin plugins in seconds
END
        for my $plugin (@plugins) {
            my ($time, $name) = @$plugin;
            my $fieldname = clean_fieldname($name);
            print <<END;
$fieldname.label $name
$fieldname.info The processing time of $name
$fieldname.draw AREASTACK
END
        }
    }
    default {
        for my $plugin (@plugins) {
            my ($time, $name) = @$plugin;
            my $fieldname = clean_fieldname($name);
            print <<END;
$fieldname.value $time
END
        }
    }
}

sub slurp {
    do {
        local (@ARGV, $/) = shift;
        scalar <>;
    };
}

sub parse_plugin_time
{
    my ($file) = @_;

    my $cont = slurp($file);

    my @plugins;
    while ($cont =~ /^ (?<time>[\d.]+) \s+ (?<plugin>.*) $/mgx) {
        push @plugins => [ $+{time} => $+{plugin} ];
    }

    # Sort by size
    @plugins = sort { $b->[0] <=> $a->[0] } @plugins;

    @plugins;
}

sub plugin_names {
    map { basename $_ } grep { -x } glob "/etc/munin/plugins/*";
}

sub plugin_times {
    my (@p) = @_;
    my %time;

    my $dir = tempdir("munin-stats-plugins-XXXX", CLEANUP => 1, TMPDIR => 1);

    for my $plugin (@p) {
        my ($fh, $file) = tempfile(DIR => $dir);
        my $t0 = [gettimeofday];
        if (system qq[MUNIN_STATS_PLUGINS_RELOAD=0 munin-run "$plugin" >"$file" 2>&1]) {
            my $cont = slurp($file);
            die "munin-run: Failed to run plugin $plugin: $?, output: $cont";
        }
        my $t1 = [gettimeofday];

        my $elapsed = tv_interval($t0, $t1);
        $time{$plugin} = sprintf "%0.2f", $elapsed;
    }

    return \%time;
}

sub write_plugin_times {
    my ($tmp, $real, $time) = @_;

    # Write out the runtimes to a tempfile
    open my $fh, ">", $cache_tmp;
    while (my ($p, $t) = each %$time) {
        say $fh "$t $p";
    }
    close $fh;

    # Rename the temp to the real thing. If we wrote it to begin
    # with we might have a race condition.
    rename $cache_tmp, $cache;
}