(named after Randle McMurphy - because this approach miight be slightly deranged)

Given a pool of servers, and a bunch of provisioning shell scripts, randle opens an ssh connection to each server and runs the scripts.

This application was written as a challenge for a job interview with Slack.com, but since I worked quite hard on it, I thought it might be of interest to others.

• Multiple servers can be provisioned simultaneously

• Un-opinionated provisioning - they're your provisioning scripts

• Idempotent, only performs the provisioning tasks that need to be done

A command like this will connect to three servers and provision them with the scripts in the directory you specify:

python -m randle -d server-todo/ -u USERNAME -p PASSWORD -a 192.168.1.7 -a 192.168.1.8 -a 192.168.1.9 

And take a quick look at the options:

python -m randle --help

Note: if you run python setup.py install --user it will build a standalone randle binary in ~/.local/bin/.

The -d argument lets you specify a folder that contains provisioning scripts that you want to execute on a server. It is up to you to make your scripts idempotent. Ensure your scripts exit with a non-zero status if they fail.

server-todo/004-update-config.sh

#!/bin/bash

grep "some config option" /etc/config.something || run=1

if [ "${run}" ]; then
  echo "Missing the config option! Writing it now..." > /dev/stderr
  echo "some config option" > /etc/config.something
fi

Note that by echoing some info to stderr, this tool interprets that as a message that the user should see.

• Interrogate a load balancer to dynamically determine the instances beneath it that require provisioning

• Support for pre-hook operations and post-hook operations (for deploy strategies)

• Or built-in deployment strategies, rolling, blue-green, red-black, canary deployment?

• Scripts are not OS agnostic. Ie, apt vs yum etc. But the OS agnostic abstraction can be pretty leaky.

• Only does IP addresses at the moment (doesn't resolve hostnames)

• The pre-hook could provision a brand new server(s) and could theoretically return the IP address to the main randle process in some fashion, so that the new server can be provisioned (for eg red-black deploys)

• Add support for privilege escalation, and ssh keys for auth

• Python 2.7.9 (it may Just Work on other versions too)

• Python Paramiko (I'm using python-paramiko/stable,now 1.15.1-1 on debian:jessie)