Varnish Object Banner

varnishbanner.py

#!/usr/bin/env python3
"""
Very simple Proof of Concept to read lines coming from
varnishncsa and send them out as events using Serf.

In this case Varnish is used in front of Ceph RGW and
we want to achieve cache consistency.

Send out a event using Serf when a PUT, POST or DELETE
is received so that all nodes can issue a varnish ban.

In the future this should probably be a script with threads
and Queues where incoming lines are put in a queue, combined
and send out as a single Serf event every 500ms or so to prevent
way to many forking and events in Serf.

Not of concern now for this PoC.

varnishncsa -F '%m %{Host}i %U %{Bucket}o %s'|varnishbanner

Author: Wido den Hollander <wido@widodh.nl>
"""
import sys
import json
import subprocess

SERF_BINARY = "/usr/local/bin/serf"

while True:
    try:
        line = sys.stdin.readline().strip()
        method, host, url, bucket, status = line.split()

        if int(status) > 400:
            pass

        if method == "PUT":
            ban = {'host': host, 'url': url, 'bucket': bucket}
            subprocess.call([SERF_BINARY, "event", "varnishban", json.dumps(ban)])
    except KeyboardInterrupt:
        break