davydovanton

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

davydovanton

http://www.facebook.com/sharer.php?u={url}&t={title}
http://www.liveinternet.ru/journal_post.php?action=n_add&cnurl={url}&cntitle={title}
http://www.livejournal.com/update.bml?event={url}&subject={title}
http://connect.mail.ru/share?url={url}&title={title}
http://www.odnoklassniki.ru/dk?st.cmd=addShare&st._surl={url}&title={title}
http://twitter.com/share?text={title}&url={url}
http://vkontakte.ru/share.php?url={url}
http://www.google.com/buzz/post?message={title}&url={url}
http://del.icio.us/post?url={url}&title={title}
http://digg.com/submit?url={url}&title={title}&media=news&topic=people&thumbnails=0

davydovanton

# Check type class in STI in rails
Post.uniq.pluck(:type).each do |class_type|
  method_name = class_type.gsub(/([a-z\d])([A-Z])/, '\1_\2').downcase + '?'
  define_method method_name do
    type == class_type
  end
end

# Use mb_chars.uppcase for many varibles
first_name, middle_name, last_name = [:first_name, :middle_name, :last_name].map{ |i| user.send(i).mb_chars.capitalize }

davydovanton

for i in */.; do
  cd $i
  repo=$(git remote show origin | grep 'Fetch URL:')
  re="Fetch URL: https://github.com/(.+)"
  if [[ $repo =~ $re ]]; then
    var="$var\nPlugin '${BASH_REMATCH[1]}'"
  fi
  cd -
done

davydovanton

" Tools for searching and replacing text in Vim
 
" Search for the current visual selection
fun! StarSearch(direction)
  let old_reg = getreg('"')
  let old_regtype = getregtype('"')
  exe 'normal! gvy\<esc>gV'
  let @/ = EscapeMagic(@")
  call histadd("/", @/)
  call setreg('"', old_reg, old_regtype)

davydovanton

#!/usr/bin/env ruby
 
require 'rubygems'
require 'sinatra'
 
get '/' do
  erb :index
end
 
get '/follower_viz' do

davydovanton

require 'thread'

mutex = Mutex.new
condvar = ConditionVariable.new

puts "start"
Thread.new do
  puts "in thread"
  sleep 5
  puts "after thread sleep"

davydovanton

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:

davydovanton

#include <stdlib.h>
#include <math.h>

int ffi_pow(int a, int n) {
  return pow(a, n);
}

davydovanton

module Jekyll
  module Tags
    # Simple jekyll plugin for create a html figure construction.
    # About figure:
    #   https://developer.mozilla.org/en-US/docs/Web/HTML/Element/figure
    #
    # The figure tag should take this form:
    #
    #   {% image_with_caption you_image_url %}
    #     This is caption block. This should be parsed as *markdown* [man](http://example.com/). Or not :)