Munin plugin for analysing xferlog (e.g. by vsftpd)

xferlog.rb

#!/usr/bin/ruby

LOGFILE   = ENV["LOGFILE"]   || "/var/log/vsftpd.log"
STATEFILE = ENV["STATEFILE"] || "#{ENV["MUNIN_PLUGSTATE"]}/munin-xferlog.state"
ROTLOGFILE = "#{LOGFILE}.1"

LOGFILE.freeze
STATEFILE.freeze
ROTLOGFILE.freeze

$asciitransfers = 0
$bintransfers = 0

def usage
  puts "Usage: $0 [config]"
  puts "This munin plugin monitors the FTP transfers over time."
end

def parse_logfile(filename, start, fin)
  File.open(filename, "rb") do |file|
    file.seek(start)

    # It is guaranteed that fin is never beyond EOF.
    # It can be equal to EOF, but that's okay. But
    # if data has been written to the file while this
    # programme is running, it will be smaller than EOF.
    while file.tell < fin
      line = file.gets.chomp.split(/\s+/)
      if line[9] == "a"
        $asciitransfers += line[7].to_i
      elsif line[9] == "b"
        $bintransfers += line[7].to_i
      end
    end
  end
end

def get_values
  # If the logfile is not there, indicate failure to munin.
  unless File.exist?(LOGFILE)
    puts "xferlog_ascii.value U"
    puts "xferlog_binary.value U"
    exit 2
  end

  # Read values from last run
  pos = nil
  if File.exist?(STATEFILE)
    str = File.read(STATEFILE)
    pos, $asciitransfers, $bintransfers = str.split(":").map(&:to_i)
  else
    # Initial run, start at zero
    $asciitransfers = 0
    $bintransfers  = 0
  end

  # Determine size of logfile
  logsize = File.size(LOGFILE)

  # If pos is not set, the statefile did not exist,
  # i.e. this is the first run of the plugin. Use
  # the current logfile size as the starting point
  # (makes the first run a no-op).
  pos = logsize unless pos

  # If the size of the logfile is smaller than the
  # last handled position, the log has been rotated.
  # Process the rotated logfile prior to the current
  # logfile, if that file exists.
  if logsize < pos
    if File.exist?(ROTLOGFILE)
      parse_logfile ROTLOGFILE, pos, File.size(ROTLOGFILE)
    end

    # Process the current logfile from the beginning again.
    pos = 0
  end

  # Now parse the current logfile (use determined logsize
  # to ignore data written to the logfile while this programme
  # is running).
  parse_logfile LOGFILE, pos, logsize
  pos = logsize

  # Tell munin
  puts "xferlog_ascii.value #$asciitransfers"
  puts "xferlog_binary.value #$bintransfers"

  # Remember where we left off
  File.open(STATEFILE, "w") do |f|
    f.write("#{pos}:#$asciitransfers:#$bintransfers")
  end
end

case ARGV.count
when 0
  get_values
when 1
  if ARGV.first == "config"
    puts "graph_title FTP Transfers"
    puts "graph_category network"
    puts "graph_args --base 1000 -l 0"
    puts "graph_vlabel Bytes/\${graph_period}"
    puts "xferlog_ascii.label ASCII Transfers"
    puts "xferlog_ascii.type DERIVE"
    puts "xferlog_ascii.draw AREA"
    puts "xferlog_ascii.min 0"
    puts "xferlog_binary.label Binary Transfers"
    puts "xferlog_binary.type DERIVE"
    puts "xferlog_binary.draw STACK"
    puts "xferlog_binary.min 0"
  else
    usage
    exit 1
  end
else
  usage
  exit 1
end

exit 0