Benjamin Dos Santos bdossantos

Zero downtime deploys with unicorn + nginx + runit + rvm + chef

Below are the actual files we use in one of our latest production applications at Agora Games to achieve zero downtime deploys with unicorn. You've probably already read the GitHub blog post on Unicorn and would like to try zero downtime deploys for your application. I hope these files and notes help. I am happy to update these files or these notes if there are comments/questions. YMMV (of course).

Other application notes:

Our application uses MongoDB, so we don't have database migrations to worry about as with MySQL or postgresql. That does not mean that we won't have to worry about issues with the database with indexes being built in MongoDB or what have you.
We use capistrano for deployment.

Salient points for each file:

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

Locate the section for your github remote in the .git/config file. It looks like this:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	url = [email protected]:joyent/node.git

Now add the line fetch = +refs/pull/*/head:refs/remotes/origin/pr/* to this section. Obviously, change the github url to match your project's URL. It ends up looking like this:

This document has now been incorporated into the uWSGI documentation:

http://uwsgi-docs.readthedocs.org/en/latest/tutorials/Django_and_nginx.html

Set up Django, nginx and uwsgi

Steps with explanations to set up a server using:

	#!/bin/bash
	set -e

	# Usage:
	# rsync_parallel.sh [--parallel=N] [rsync args...]
	#
	# Options:
	# --parallel=N Use N parallel processes for transfer. Defaults to 10.
	#
	# Notes:

	$ augtool
	> set /augeas/load/Spacevars/incl[last()+1] "/etc/redis/redis.conf"
	> load
	> print /files/etc/redis/redis.conf

	# Class: base::swap
	#
	# This class manages swapspace on a node.
	#
	# Parameters:
	# - $ensure Allows creation or removal of swapspace and the corresponding file.
	# - $swapfile Defaults to /mnt which is a fast ephemeral filesystem on EC2 instances.
	# This keeps performance reasonable while avoiding I/O charges on EBS.
	# - $swapfilesize Size of the swapfile in MB. Defaults to memory size, but see Requires.
	#

	#!/bin/bash -e
	# These need to be set.
	#export EC2_HOME="/path/to/ec2-api-tools"
	#export AWS_ACCESS_KEY='XXXXXXXXXXXXXXXXXXXX'
	#export AWS_SECRET_KEY='XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
	#export PATH="$PATH:${EC2_HOME}/bin"

	ami_id='ami-123abc12'
	availability_zone='eu-west-1a'
	keypair="[email protected]"

	import boto.ec2.cloudwatch
	import sys
	import os

	AWS_KEY = os.environ.get("AWS_ACCESS_KEY_ID")
	AWS_SECRET = os.environ.get("AWS_SECRET_ACCESS_KEY")
	AWS_REGION = os.environ.get("AWS_EC2_REGION", "us-east-1")
	TOPIC = 'YOUR_TOPIC'

	def create_status_alarm(instance_id):

	####################################
	# BASIC REQUIREMENTS
	# http://graphite.wikidot.com/installation
	# http://geek.michaelgrace.org/2011/09/how-to-install-graphite-on-ubuntu/
	# Last tested & updated 10/13/2011
	####################################

	cd
	sudo apt-get update
	sudo apt-get upgrade