Vanja Radovanović elvanja

Introduction to Kafka

Kafka acts as a kind of write-ahead log (WAL) that records messages to a persistent store (disk) and allows subscribers to read and apply these changes to their own stores in a system appropriate time-frame.

Terminology:

Producers send messages to brokers
Consumers read messages from brokers
Messages are sent to a topic

Recommended code reading from Ruby Parley

Ruby

cane: https://github.com/square/cane
Capybara: https://github.com/jnicklas/capybara
REST Client: https://github.com/archiloque/rest-client
Savon: https://github.com/savonrb/savon
Unicorn: https://github.com/defunkt/unicorn

1. Get You a Hug, Every Friday

FridayHug.com http://fridayhug.com

2. Run From a Single File

The Smallest Rails App http://thesmallestrailsapp.com

%w(action_controller/railtie coderay).each &method(:require)

	-- show running queries (pre 9.2)
	SELECT procpid, age(clock_timestamp(), query_start), usename, current_query
	FROM pg_stat_activity
	WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%'
	ORDER BY query_start desc;

	-- show running queries (9.2)
	SELECT pid, age(clock_timestamp(), query_start), usename, query
	FROM pg_stat_activity
	WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'

	RAILS_ENV=production rake db:setup
	# produces the error below.....hmmm.....it's a no-worky
	psql:/yourprojectpath/yourproject/db/structure.sql:29: ERROR: could not open extension control file "/usr/share/postgresql/9.1/extension/hstore.control": No such file or directory

	# hstore postgresql extension needs to be installed, so....
	sudo apt-get install postgresql-contrib

	# now your extension should be available to enable so log in with psql
	psql -d yourproject_production -U yourdbuser -W

	# MOTIVATION: As rails apps are growing, people are noticing the drawbacks
	# of the ActiveRecord pattern. Several apps I have seen, and several
	# developers I have spoken to are looking towards other patterns for object
	# persistence. The major drawback with ActiveRecord is that the notion
	# of the domain object is conflated with what it means to store/retrieve
	# it in any given format (like sql, json, key/value, etc).
	#
	# This is an attempt to codify the Repository pattern in a way that would
	# feel comfortable to beginner and seasoned Ruby developers alike.
	#

	gem 'pg'
	group :development do
	gem 'ruby-debug'
	end
	gem 'rake', '~> 0.8.7'
	gem 'devise'
	gem 'oa-oauth', :require => 'omniauth/oauth'
	gem 'omniauth'
	gem 'haml'
	gem 'dynamic_form'

	source :gemcutter

	gem 'goliath', :git => 'git://github.com/postrank-labs/goliath.git'
	gem 'em-synchrony', :git => 'git://github.com/igrigorik/em-synchrony.git'

	--colour
	-I app