#!/usr/bin/python3
# check_vgfree - Nagios plugin to check free space on LVM volume group



from __future__ import print_function, division
import optparse
import os
import subprocess
import sys



# Subclass to return code 3 at error.
class OptionParser(optparse.OptionParser):
    def error(self, msg=None):
        self.print_usage(sys.stderr)
        self.exit(3, "%s: error: %s\n" % (self.get_prog_name(), msg))



class NagiosStatus(Exception):
    Label = ['OK', 'WARNING', 'CRITICAL', 'UNDEFINED']

    def __init__(self, code, message):
        self.code = code
        self.message = message

    def __str__(self):
        return "%s - %s" % (NagiosStatus.Label[self.code], self.message)

    def returnStatus(self):
        print(self)
        sys.exit(self.code)



def parsecmdline():
    "Parse command line options."
    usage = 'Usage: %prog [options]\n  try: %prog --help'
    optionparser = OptionParser(usage)
    optionparser.add_option("-c", "--critical", type="float", default=0,
        help="critical size limit")
    optionparser.add_option("-C", "--critical-percent", type="float", dest="cp",
        default=0, help="% critical limit")
    optionparser.add_option("-g", "--volume-group", dest="vg", default="vg0",
        help="volume group to check")
    optionparser.add_option("-w", "--warning", type="float", default=0,
        help="warning size limit")
    optionparser.add_option("-W", "--warning-percent", type="float", dest="wp",
        default=0, help="% warning limit")
    optionparser.add_option("--units", type="choice", dest="unit", default="g",
        choices=("b", "k", "m", "g", "t", "p", "e"),
        help="size in these units: (b)ytes, (k)ilobytes, (m)egabytes, "
        "*(g)igabytes (*DEFAULT), (t)erabytes, (p)etabytes, (e)xabytes")
    options, args = optionparser.parse_args()
    return options



def pickvgscommand():
    "Pick vgs command path"
    command = "/sbin/vgs"
    if not os.path.isfile(command):
        command = "/usr" + command
        if not os.path.isfile(command):
            msg = 'vgs command not found (is lvm2 package installed?)'
            raise NagiosStatus(3, msg)
    return command



def pickvgspace(vg, unit):
    "Pick free space on volume group."
    command = pickvgscommand()
    command = [command, "--noheadings", "--nosuffix",
        "--options=vg_size,vg_free", "--units=%s" % unit, vg]
    environment = {"LANG": "C"}
    process = subprocess.Popen(command, stdout=subprocess.PIPE,
        stderr=subprocess.PIPE, env=environment)
    output, error = process.communicate()
    if 0 < process.returncode:
        error = error.split('\n')[0].strip()
        raise NagiosStatus(3, error)
    size, free = [float(x) for x in output.split()]
    return size, free



def checkstatus(free, percent, vg, critical, cp, warning, wp, unit):
    "Check the limits."
    result = "%g%sB (%g%%) free on volume group %s" % (free, unit.upper(),
        percent, vg)
    if 0 < critical and free <= critical or 0 < cp and percent <= cp:
        return NagiosStatus(2, result)
    elif 0 < warning and free <= warning or 0 < wp and percent <= wp:
        return NagiosStatus(1, result)
    else:
        return NagiosStatus(0, result)



def main():
    # Parse command line options.
    options = parsecmdline()

    # Pick free space on volume group.
    try:
        size, free = pickvgspace(options.vg, options.unit)
    except NagiosStatus as ns:
        ns.returnStatus()
    percent = 100 * free / size

    # Check the limits.
    ns = checkstatus(
        free,
        percent,
        options.vg,
        options.critical,
        options.cp,
        options.warning,
        options.wp,
        options.unit
    )
    ns.returnStatus()



if __name__ == '__main__':
    main()