#lsrc

These are some of my (terse) notes from day two of the LSRC.  It would probably be helpful to read my colleague's notes as well.

Blow up Your Views

Instance variables in views suck

Real interface between C/V (github: voxdolo/decent_exposure)

Added "exposes(:foo)" in the controller and the view starts using just "foo" instead of "@foo"

Kill helpers

Example of timestamps

Should be writing helpers to format timestamps

Usually helpers are for specific objects (e.g. formats the timestamp on a particular kind of object)

We write helpers like print_name(user) instead of user.print_name but we want the later.

View Objects Implemented

Create an /app/decorators folder

Implement an attr_accessible approach to the view: Limit what it is allowed to call.

Github: jcasimir/draper

Should be splitting up responsibilities

Always render the same thing from the controller (define an API)

The view should deal with drawing the display for the client

Send them a JS template, assets, etc.

Render Engines

Plain HTML with jQuery Replacement

Mustache

Handlebars (SproutCore)

ICanHazJS

ZeroMQ

ZeroMQ is a messaging bus

Zero stands for 'zero brokers'

Scalability

Serve requests faster

Deals with complexity scalability

Uses an actor model

stateless

self-contained pieces

What ZeroMQ isn't

ZeroMQ isn't designed to write an HTTP server

It doesn't care what you send in messages but it cares how it sends it

ZeroMQ sockets only talk to other ZeroMQ sockets

Could write a layer that interprets HTTP and sends it into ZeroMQ (Mongrel2)

How to use it

Ruby: gem install zmq

Based in C and supported in every language

Threadsafe but can't share a socket between threads

Example: Request/Reply Sockets

Can start a client and it starts trying to communicate but will block until the server responds

If the server crashes in the middle and restarts but it wont automatically work.

Publish/Subscribe model

Uses option "SUBSCRIBE"

If the publisher goes down, the subscriber is durable

Push/Pull sockets

Multiple pull sockets can bind to a single push socket

Spawn more workers if the queue is backing up

Durable Sockets

Set a socket identity: give it a name

Setup spooling to disk for unreceived messages

JavaScript for people who didn't learn JavaScript (@jwo)

Prototype Inheritance

Only one prototype per function (but can be switched out when needed)

Like Ruby modules but you only get one.

Calling super

JavaScript doesn't provide a method to call super

var Note = Backbone.Model.extend({   set: function(...) { } <-- override behavior and call Backbone.Model.set.call(...)

Using 'new'

Don't just use new because you think you have to

Use 'new' if you need the prototype of the object

Don't use it if your just creating a new Array, etc.

Object.create is useful but some browser dependencies

"Don't write new Array()"

Arrays in JS don't have limits

"Don't write new Function()" - just use the funciton() literal

Invocation

Functions get declared-parameters, this, and arguments

Creating a new object with Object.create(HelloWorld) and calling hi.speak() you get the prototype

Using just HelloWorld.speak doesn't provide scope so 'this' isn't bound to the object

JavaScript allows you to pass in the object that you want 'this' to reference (so function() in the method can actually operate on whatever object you provide)

JavaScript puts semicolons in where you "forgot them"

return {   javascript: "foo" }; // This will fail because return gets a magic ';' on the end.

Testing JavaScript with Jasimine

Slides: http://bit.ly/jasmine-lsrc

Jasmine has rspec like syntax

Jasmine with jQuery

jasmine-jquery adds more matchers

Lettering.js

Allows you to throw spans in between chars in a particular HTML DOM element

SpecRunner.html

Added jquery and lettering js files

Jasmine with Rails

Add 'jasmine' to Gemfile

rake jasmine / rake jasmine:ci

Easier way with Evergreen "gem install evergreen"

Create public folder (with js in it)

Create spec folder with specs in it

evergreen run

Evergreen follows the name_spec.js file naming convention

Install coffee-script and works with Jasmine (make .coffee file)

Headless running

Install capybara-webkit

Switched from selenium to webkit and runs faster

Rosie gives you factory_girl for JS

github: bkeepers/rosie

jasminerice - jasmine + coffee script + rails 3.1

The Ballad of Goliath, EventMachine, and MongoDB

These notes are bit short since a lot of the talk was random aspects of MongoDB towards the end.

Goliath

Event Driven (Built upon EventMachine)

Web and app server

Uses fibers in Ruby 1.9

Matches a rackup app somewhat

Inherits from Goliath::API

Get an array of command line options

-u for actually specifying the user

By default it doesn't log at all

EventMachine: Watch peepcode screencode

MongoDB

Just doing Mongo::ReplSetConnection.new(host), only R/W to primary

Use Mongo::ReplSetConnection.new(host, :read_secondary => true) to get better read performance

Polygot Parallelism

This talk started off with a brief intro to Erlang and continued a discussion into how Rackspace was able to successfully solve a massively parallel data gathering problem.

Erlang

Immutable Data Structures

Single assignment => everything is immutable

Webmachine

Similar to Sinatra or Goliath

Basically developing a custom web server for your application's behavior.

http://webmachine.basho.com