Very simple munin plugin to graph nginx HTTP error codes

nginx_error_rate.py

#!/usr/bin/python3
'''
Monitors error rates based on the Nginx access log.
By default triggers an warn alert at 2 req/s and critical for 4 req/s for each status code.
Some of the less common status codes have been commented out. Customize accordingly for yourself.

ALL FAME GOES HERE : https://gist.github.com/mipearson/1146151

Install:
wget https://gist.github.com/Lusitaniae/fb8532294b1cfba7aceffa1e2dd2a264 -O /usr/share/munin/plugins/nginx_error_rate;
ln -s /usr/share/munin/plugins/nginx_error_rate /etc/munin/plugins/;
chmod +x /etc/munin/plugins/nginx_error_rate;

Test:
munin-run nginx_error_rate;
munin-run nginx_error_rate config;

Munin conf (optional):
[nginx*]
  user root
  env.access_log /var/log/nginx/blogs.access.log

'user root' might be necessary if you have permission errors.

'''
import re, sys, os

CODES = {
  '400': 'Bad Request',
  '401': 'Unauthorized',
  '403': 'Forbidden',
  '404': 'Not Found',
#  '405': 'Method Not Allowed',
#  '406': 'Not Acceptable',
#  '408': 'Request Timeout',
#  '499': 'Client Connection Terminated',
  '500': 'Internal Server Error',
  '502': 'Bad Gateway',
  '503': 'Service Unavailable',
  '504': 'Gateway timeout',
#  'Other': 'Other responses'
}

ACCESS_LOG = "/var/log/nginx/access.log"
if 'access_log' in os.environ:
  ACCESS_LOG = os.environ.get('access_log')

if len(sys.argv) > 1 and  sys.argv[1] == 'config':
  print ("graph_title nginx Error Codes")
  print ("graph_vlabel responses per minute")
  print ("graph_category nginx")
  print ("graph_period minute")
  print ("graph_info Non-200 response codes per minute")
  for code in  CODES:
    print ("stat%s.label %s %s" % (code, code, CODES[code]))
    print ("stat%s.type DERIVE" % (code))
    print ("stat%s.min 0" % (code))
    print("stat%s.warning 2" % code)
    print("stat%s.critical 4" % code)
else:
  results = {k:0 for k in CODES}
  with open(ACCESS_LOG, 'r') as f:
    for line in f.readlines():
      code = re.search(" (\d\d\d) ", line)
      if code:
        code = code.group(0).strip()
        if code in CODES:
          results[code] += 1
#        elif int(code) >= 400:
#          results['Other'] += 1

  for k in results:
    print("stat%s.value %s" % (k, results[k]))