Devops

Imagine following setup. As surly mentions somewhen in this blog, we are running a cloud based on OpenStack. The team, I am working in, is responsible to provision new nodes to the cluster, and manage the lifecycle of the existing ones. We also deploy OpenStack and related services to our fleet. One hugh task is running OpenStack high available. This seems not too difficult, but also means, we have to make each component OpenStack depends on, HA as well. So we use Galera as Database, Quobyte as a distributed storage, clustered RabbitMQ, clustered Cassandra, Zookeeper, and things I may have forgotten.

I just wanted to monkey patch the puppet package provider for gentoo portage.

But why?

# puppet resource package

Only shows packages installed by puppet, but not packages installed by hand. The apt/dpkg- and yum/rpm-provider list all packages.

It was not enough to place a lib/puppet/provider/package/portage.rb. In all my tests, the original behavior was kept. I only want to replace one function.

But how?

When registering new type or providers, etc, puppet is doing a bunch of magick in the background. So first, I have to figure out the name of the automagically created class.

Redis has a buildin pubsub mechanism, but by default it is not possible to listen on specific keys. Redis 2.8 intruduced Keyspace Notifications , to which you can subscribe.

First of all. This feature is disabled by default, so we need to enable it

$ redis-cli config set notify-keyspace-events KAE

This little python-script listens on keyspace-Events containing stash:silence/*

#!/usr/bin/env python

import redis

r = redis.StrictRedis()

pubsub = r.pubsub()
pubsub.psubscribe('__keyspace@*:stash:silence/*')
for msg in pubsub.listen():
    print(msg)

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