#!/usr/bin/perl -w
# Author: Nicolas Mendoza <nicolasm@opera.com> - 2008-06-18
#
# Monitors the average time requests matching a custom regexp takes
# For instance monitor time execution of files in http://example.com/foo/bar, 
# requests from google, images etc.
#
# Simply add an entry in the 'type' hashref and modify the description fields
# for munin, and make the 'matches' member contain a subref that returns
# true if a request matches, parameters are a list containing the request
# split on spaces.
#
# NOTE: You need to add a field in your Apache logs showing time executed.
# This is normally done using the %T (seconds) or %D (microseconds)
# For instance: 
#   LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\" %T %v"
# Check http://httpd.apache.org/docs/2.2/mod/mod_log_config.html#formats for more info
#
# Configurable variables
# 	fieldno      - Override the default field number
#   linecount    - How many last request to consider
#%# family=auto

use strict;

my $LAST_N_REQUESTS = exists $ENV{'linecount'} ? $ENV{'linecount'} : 100000; # calculate based on this amount of requests
my $TIME_FIELD_INDEX =  exists $ENV{'fieldno'} ? $ENV{'fieldno'} : -2; # second last field
my $ACCESS_LOG_PATTERN = '/var/log/apache2/access.log.*'; # log pattern, if many it will take the last one.

my $config =<< "CONFIG"
graph_title Apache average seconds last $LAST_N_REQUESTS requests
graph_args --base 1000
graph_scale no
graph_vlabel Average request time
graph_category Apache
graph_info This graph shows average request times for the last $LAST_N_REQUESTS requests
CONFIG
;

my $types = {
  # any kind of request
  total => {
    munin_fields => {
      label => 'All requests',	
      draw => 'LINE2',
      info => 'Average seconds per any request',
    },
    sum => 0,
    lines => 0,
    matches => sub { 
      return 1; 
    },
  },

  # image requests
  images => {
    munin_fields => {
      label => 'Image requests',
      draw => 'LINE2',
      info => 'Average seconds per image request',
    },
    sum => 0,
    lines => 0,
    matches => sub { 
      my ($fields) = @_; 
      my $script; 
      ($script = $fields->[6]) =~ s/\?.*\z //mx; 
      return $script =~ m{ \.(png|jpe?g|jpg|gif|tiff|ilbm|tga) \z }mx; 
    },
  },
};

if (defined(@ARGV) && ($ARGV[0] eq 'config')) {

  print $config;

  foreach my $type (keys %{$types}) {
    foreach my $key (keys %{$types->{$type}->{'munin_fields'}}) {
      printf "%s.%s %s\n", ($type, $key, $types->{$type}->{'munin_fields'}->{$key});
    }
  }
  exit(0);
}    

my $config_file = `ls -1 $ACCESS_LOG_PATTERN | tail -n 1`;

chomp $config_file;

my @lines = `tail -n $LAST_N_REQUESTS "$config_file"`;

foreach my $line (@lines) {
  foreach my $type (keys %{$types}) {
    my @fields = split /\s+/, $line;
    if ($types->{$type}->{'matches'}(\@fields)) {
      $types->{$type}->{'sum'} += $fields[$TIME_FIELD_INDEX];
      $types->{$type}->{'lines'}++;
    }
  }
} 

foreach my $type (keys %{$types}) {
  my $value = $types->{$type}->{'lines'} ? $types->{$type}->{'sum'} / $types->{$type}->{'lines'} : 'U';
  printf "%s.value %s\n", ($type, $value);
}