#!/usr/bin/env python3
# -*- python -*-

"""
=head1 INTRODUCTION

Plugin to monitor the MySQL audit log connection count

=head1 APPLICABLE SYSTEMS

MySQL needs to be configured manually in order to enable the audit log. This
can be done as follows:

=over 2

      plugin-load = server_audit=server_audit.so
      server_audit_events = connect
      server_audit_output_type=file
      server_audit_file_path = /var/log/mysql/audit.log
      server_audit_file_rotate_size = 512M
      server_audit_logging = ON
      server_audit_file_rotations = 5

=back

=head1 INSTALLATION

Place in /etc/munin/plugins/ (or link it there using ln -s)

=head1 CONFIGURATION

Add this to your /etc/munin/plugin-conf.d/munin-node:

=over 2

      [mysql_audit]
      user mysql
      env.logfile /var/log/mysql/audit.log
      env.sorted 1 # sort output (if not: unsorted)
      env.toplist 10 # only the top 10 (if unset: all of them). implies sorted

=back

=head1 HISTORY

2017-11-03: v 1.0 Bert Van de Poel <bert@bhack.net>: created
2020-07-19: v 1.1 pcy <pcy@ulyssis.org>: added config options

=head1 USAGE

Parameters understood:

  config   (required)
  autoconf (optional - used by munin-config)

=head1 MAGIC MARKERS

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


from datetime import datetime, timedelta, timezone
import operator
import os
import struct
import sys


def weakbool(x):
    return x.lower().strip() in {'true', 'yes', 'y', '1'}


logfile = os.getenv('logfile', '/var/log/mysql/audit.log')
toplist = int(os.getenv('toplist', '0'))
sortlist = weakbool(os.getenv('sorted', 'N')) or toplist > 0

STATEFILE = os.getenv('MUNIN_STATEFILE')


def loadstate():
    if not os.path.isfile(STATEFILE):
        return None

    with open(STATEFILE, 'rb') as f:
        tstamp = struct.unpack('d', f.read())[0]
        return datetime.fromtimestamp(tstamp, tz=timezone.utc)


def savestate(state):
    with open(STATEFILE, 'wb') as f:
        f.write(struct.pack('d', state.timestamp()))


def reverse_lines(filename, BUFSIZE=4096):
    with open(filename, "r") as f:
        f.seek(0, 2)
        p = f.tell()
        remainder = ""
        while True:
            sz = min(BUFSIZE, p)
            p -= sz
            f.seek(p)
            buf = f.read(sz) + remainder
            if '\n' not in buf:
                remainder = buf
            else:
                i = buf.index('\n')
                for L in buf[i + 1:].split("\n")[::-1]:
                    yield L
                remainder = buf[:i]
            if p == 0:
                break
        yield remainder


def get_data(do_save=True):
    occurrences = {}
    begin = datetime.now(timezone.utc)
    begin_local = datetime.now()

    state = loadstate()
    if state is None:
        # need to do something here to prevent reading indefinitely
        state = begin - timedelta(minutes=5)

    for line in reverse_lines(logfile):
        if ',CONNECT,' not in line:
            continue

        split = line.split(',')
        key = split[2]
        date = datetime.strptime(split[0], '%Y%m%d %H:%M:%S')
        # hack to add timezone data to the datetime
        date = begin + (date - begin_local)

        if date < state:
            break

        occurrences[key] = occurrences.get(key, 0) + 1

    if do_save:
        savestate(begin)

    return occurrences


def autoconf():
    print("no (logfile not found)" if os.path.isfile(logfile) else "yes")


def configure():
    print('graph_title MySQL Audit connect count')
    print('graph_vlabel Connections')
    print('graph_category mysql')

    occurrences = get_data(False)
    occitems = occurrences.items()
    occitems = sorted(occitems, key=operator.itemgetter(1 if sortlist else 0),
                      reverse=sortlist)
    if toplist > 0:
        occitems = occitems[:toplist]

    for key, value in occitems:
        print('{}.label {}'.format(key.lower(), key))
        print('{}.type GAUGE'.format(key.lower()))
        print('{}.draw AREASTACK'.format(key.lower()))


def fetch():
    occurrences = get_data()
    occitems = occurrences.items()
    occitems = sorted(occitems, key=operator.itemgetter(1 if sortlist else 0),
                      reverse=sortlist)
    if toplist > 0:
        occitems = occitems[:toplist]

    for key, value in occitems:
        print('{}.value {}'.format(key, value))


if len(sys.argv) == 2 and sys.argv[1] == "autoconf":
    autoconf()
elif len(sys.argv) == 2 and sys.argv[1] == "config":
    configure()
else:
    fetch()