#!/usr/bin/env python
#%# family=auto
#%# capabilities=autoconf


"""
=head1 NAME

	nsd - Munin plugin to monitor the number of queries a running process
	      of nsd3 has recievied.

=head1 APPLICABLE SYSTEMS

	Linux or *nix system with a logging installation of NSD v3 installed.
	  (http://nlnetlabs.nl/projects/nsd/)

=head1 CONFIGURATION

	The plugin needs access to the nsd logfile and the nsd pid file to
	force the running nsd process to write the current statistics.

	Tip: To see if it's already set up correctly, just run this plugin
	with the parameter "autoconf".  If you get a "yes", everything should
	work like a charm already.

	This configuration section shows the defaults of the plugin:

	The stats line is a set of space-separated values that you wish to
	retrieve from NSD.  The format is VALUE=Caption.  For spaces in a
	caption value, replace them with an underscore (_).

	[nsd]
	        env.statsfile /var/log/nsd.log
        	env.pidfile /var/run/nsd3/nsd.pid
		env.stats "A=A AAAA=AAAA MX=MX PTR=PTR TYPE252=AXFR SNXD=NXDOMAIN RQ=Total_Successful"

	If you need to set a user for the logfile to be readable, and most
	importantly, the process to receive the signal, you may specify it.
	For example:

	[nsd]
		user nsd

=head1 INTERPRETATION

	The plugin shows the number of queries that nsd has received,
	averaged over a period to gain the number of queries per second.
	For most servers, these values will be very low.  In the event
	of a misconfiguration, the plugin will return undefined values.

=head1 MAGIC MARKERS

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

=head1 VERSION

	v1.0.1

=head1 AUTHOR

	J.T.Sage <jtsage@gmail.com>

=head1 LICENSE

	GPLv2

=cut
"""

import os
import sys
import subprocess
import time
import re
import signal

STATS_FILE = os.environ.get('statsfile', '/var/log/nsd.log')
PID_FILE = os.environ.get('pidfile', '/var/run/nsd3/nsd.pid')
STATS_STRING = os.environ.get('stats', "A=A AAAA=AAAA MX=MX PTR=PTR TYPE252=AXFR SNXD=NXDOMAIN RQ=Total_Successful")

BOTH_LISTS = STATS_STRING.split()

def print_config():
	"""Generates and prints a munin config for a given chart."""

	print "graph_title NSD3 Queries"
	print "graph_vlabel qps"
	print "graph_category network"
	print "graph_info Queries per second"
	for x in BOTH_LISTS:
		val = x.split('=')
		name = val[0].lower()
		label = val[1].replace('_', ' ')
		print name + '.label ' + label
		print name + '.type DERIVE'
		print name + '.min 0'

	sys.exit(0)

def print_values():
	"""Gets NSD's latest stats."""

	bigfail = False
	if ( not os.access(STATS_FILE, os.R_OK) ) :
		bigfail = True
	if ( not os.access(PID_FILE, os.R_OK) ) :
		bigfail = True

	if ( not bigfail ):
		pidf = open(PID_FILE, 'r')
		pidn = pidf.read()
		pidf.close();
		try:
			os.kill(int(pidn.strip()), signal.SIGUSR1)
	        except OSError:
			bigfail = True


	time.sleep(.5) # Wait for the log to write.

	if ( not bigfail ):
		statf = open(STATS_FILE, 'r')
		stats = tail(statf, 10)

		nstats = []
		xstats = []

		for line in stats:
			if "XSTATS" in line:
				xstats.append(line.strip())
			if "NSTATS" in line:
				nstats.append(line.strip())

		statsline = nstats[-1] + xstats[-1]
	else:
		statsline = " "

	relist = []
	for x in BOTH_LISTS:
                val = x.split('=')
                name = val[0].lower()
		rxp = val[0]
		relist.append([name, rxp])

	for point in relist:
		matches = re.compile(' '+point[1]+'=(\d+)').findall(statsline)
		if bigfail:
			print point[0]+'.value U'
		elif matches == []:
			print point[0]+'.value 0'
		else:
			print point[0]+'.value '+matches[0]

def tail( f, window=20 ):
	f.seek( 0, 2 )
	bytes = f.tell()
	size = window
	block = -1
	while size > 0 and bytes+block*1024  > 0:
		f.seek( block*1024, 2 ) # from the end!
		data = f.read( 1024 )
		linesFound = data.count('\n')
		size -= linesFound
		block -= 1
	f.seek( block*1024, 2 )
	f.readline() # find a newline
	lastBlocks = list( f.readlines() )
	return lastBlocks[-window:]

if __name__ == '__main__':
	if len(sys.argv) > 1:
		if  sys.argv[1] == 'autoconf':
			if ( not os.path.isfile(STATS_FILE) ) :
				print 'no (Log file not found)'
			elif ( not os.path.isfile(PID_FILE) ) :
				print 'no (PID file not found)'
			elif ( not os.access(STATS_FILE, os.R_OK) ) :
				print 'no (Log file exists, access denied for read)'
                        elif ( not os.access(PID_FILE, os.R_OK) ) :
                                print 'no (PID file exists, access denied for read)'
			else:
				pidf = open(PID_FILE, 'r')
				pidn = pidf.read()
				pidf.close();
				try:
					os.kill(int(pidn.strip()), signal.SIGUSR1)
				except OSError as (errno, strerror):
					print 'no (Unable to signal process :: '+strerror+')'
					sys.exit(0)
				print 'yes'
			sys.exit(0)

	if len(sys.argv) > 1 and sys.argv[1] == 'config':
		print_config()
		sys.exit(0)

	print_values()