varnish.py

#!/usr/bin/env python
"""
Cloudkick Varnish plugin
Developed by Christopher Groskopf for The Chicago Tribune News Applications Team
http://apps.chicagotribune.com
https://github.com/newsapps

Source released under the MIT license.

Description:

This plugin will pipe all output from the command "varnishstat -1"
up to Cloudkick.  In addition, it will store the cache_hit and cache_miss stats
in a tmp file on each execution so that it can compute a hit_rate stat, which will
also be reported to Cloudkick.

Error reporting:

This plugin will report an error only if varnishstat fails to
execute (generally this would only be the case if Varnish is not running).

Warn reporting:

This plugin will report a warning anytime that it fails to parse
varnishstat's output.

TODO:

Support custom warnings and errors when the hit_rate stat falls below a
specified threshold.
"""

from __future__ import with_statement

import os
import re
import subprocess
import sys

HIT_RATE_FILE = '/tmp/cloudkick-agent-varnish.tmp'

result = subprocess.Popen(['varnishstat', '-1'], stdout=subprocess.PIPE).communicate()[0]

if not result:
    print 'status err Varnish is not running.'
    sys.exit()

data = []
hits = None
misses = None

try:
    for r in result.split('\n'):
        if not r:
            continue

        parts = re.split('\s+', r.strip())

        data.append('metric %s int %s' % (parts[0], parts[1]))

        if parts[0] == 'cache_hit':
            hits = int(parts[1])
        elif parts[0] == 'cache_miss':
            misses = int(parts[1])

    if hits and misses:
        if os.path.exists(HIT_RATE_FILE):
            with open(HIT_RATE_FILE, 'r') as f:
                parts = f.read().split(',')
                last_hits = int(parts[0])
                last_misses = int(parts[1])

            delta_hits = hits - last_hits
            delta_misses = misses - last_misses

            if delta_misses == 0:
                hit_rate = float(1.0)
            else:
                hit_rate = float(delta_hits) / (delta_hits + delta_misses)

            data.append('metric hit_rate float %1.3f' % hit_rate)

        with open(HIT_RATE_FILE, 'w') as f:
            f.write('%i,%i' % (hits, misses))
except Exception, e:
    print 'status warn Error parsing varnishstat output (%s)' % (str(e))
    sys.exit()

print 'status ok Varnish is running.'

for d in data:
    print d