Milan Rawal codemilan

Transactions

As your business logic gets complex you may need to implement transactions. The classic example is a bank funds transfer from account A to account B. If the withdrawal from account A fails then the deposit to account B should either never take place or be rolled back.

Basics

All the complexity is handled by ActiveRecord::Transactions. Any model class or instance has a method named .transaction. When called and passed a block, that block will be executed inside a database transaction. If there's an exception raised, the transaction will automatically be rolled back.

Example

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

Installation

Install fish via Brew
Optionally install Oh My Fish!
Add fish to known shells
Set default shell to fish

brew install fish  
curl -L https://get.oh-my.fish | fish

This will create a proxy server in whatever your availability zone your VPC is in. For me, that's us-east-1b. For you, that may be something different. Steps 10+ should more or less work regardless of your provider since those steps cover the setup and configuration of TinyProxy.

Click the Launch Instance button.
Choose Ubuntu Server 14.04 LTS (HVM), SSD Volume Type. This isn't strictly necessary. If you choose another OS, check its documentation for how to install new packages.
On the Choose an Instance Type screen, select t2.micro. It's Free Tier eligible.
Click the Next: ... buttons until you reach the Configure Security Group screen.
- You may wish to reduce the amount of storage on the Add Storage screen. This is optional.
- You may wish to add a tag on the Tag Instance screen. This is also optional.
On the Configure Security Group screen:

Select Create a new security group.

	# Adapted from https://rubyplus.com/articles/3401-Customize-Field-Error-in-Rails-5
	ActionView::Base.field_error_proc = Proc.new do \|html_tag, instance\|
	html = ''

	form_fields = [
	'textarea',
	'input',
	'select'
	]

	require 'net/ftp'

	CONTENT_SERVER_DOMAIN_NAME = "one-of-the-ftp-server.thought-sauce.com.hk"
	CONTENT_SERVER_FTP_LOGIN = "saucy-ftp-server-login"
	CONTENT_SERVER_FTP_PASSWORD = "saucy-ftp-server-password"


	# LOGIN and LIST available files at default home directory
	Net::FTP.open(CONTENT_SERVER_DOMAIN_NAME, CONTENT_SERVER_FTP_LOGIN, CONTENT_SERVER_FTP_PASSWORD) do \|ftp\|
	files = ftp.list

	#!/usr/bin/env bash
	#
	# Simple script to setup friendly environment for beginning Linux/Mac Ruby users
	#

	echo "installing pry and awesome_print"
	gem install -q --no-ri --no-rdoc \
	pry pry-doc pry-coolline awesome_print

	# Nifty pry config copied from https://github.com/dotphiles/dotphiles/blob/master/ruby/aprc

	# This probably isn't a good thing to want to do, but it came up for me,
	# so in the spirit of helping others with weird problems (and because this
	# seems to be documented almost nowhere):

	after_save do

	if some_failing_condition
	errors.add(:something, "some failure happened.")
	raise ActiveRecord::RecordInvalid.new(self)
	end

	# https://www.justinweiss.com/articles/search-and-filter-rails-models-without-bloating-your-controller/
	# Call scopes directly from your URL params:
	#
	# @products = Product.filter(params.slice(:status, :location, :starts_with))
	module Filterable
	extend ActiveSupport::Concern

	module ClassMethods

	# Call the class methods with the same name as the keys in <tt>filtering_params</tt>

	# This server demo does a socket hijack in Rack and then saves the socket to a global variable
	# to prevent it from being GCed when the Puma thread ends. It will then write "BEEP" to each
	# socket every ten seconds to prevent the connection timing out. During testing, it easily
	# handled up to 65523 connections, after which it ran into the `ulimit` for open file descriptors.
	# The bit with the waiting area is there because a normal `Set` is not thread safe and it would
	# drop socket due to race conditions. The `Queue` is thread safe and will make sure all sockets
	# are preserved.

	# run with `rackup -q -p 8000 -o 0.0.0.0 c10k.ru`
	# testing: install `ab` and then run `ab -c 20000 -n 20000 <ip adress of server>:8000/