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Background jobs in rails applications make our development lives easier.

We rely on them for a lot of things - common use cases include sending emails, push notifications, processing 3rd party API interactions, transactions and long-running requests that tie up server resources.

In a typical production app, there's a possibility of processing hundreds of jobs per second under normal circumstances and thousands depending on the number of users and campaign going on.

I've been using Resque for a while but recently made a switch to Sidekiq on a few apps. I initially wanted to write about the switch but I soon realized that the knowledge of introducing Sidekiq to a new project is important and the post became really long so I decided to split it. In this post, I'm going to show you how to use Sidekiq for your background jobs on a new rails app. And in part 2, I'll write about switching from an existing app on Resque to Sidekiq.

Why S

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# add scope (with one or more attributes) for has_many relationships

# This is great for polyphomism when you want different models to be able to have subscriptions; so that you don't just attach only one model to subscriptions

# Reference: http://edgeguides.rubyonrails.org/association_basics.html#scopes-for-has-many

class Question < ActiveRecord::Base
  has_many :subscriptions, -> { where "type = 'Question'" }, :foreign_key => "subscribed_item_id"
end

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# could not connect to server: No such file or directory
#  Is the server running locally and accepting
# connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

Just run this command on the terminal

rm /usr/local/var/postgres/postmaster.pid

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This guide assumes that you recently run brew upgrade postgresql and discovered to your dismay that you accidentally bumped from one major version to another: say 9.3.x to 9.4.x. Yes, that is a major version bump in PG land.

First let's check something.

brew info postgresql

The top of what gets printed as a result is the most important:

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public class MyDBHandler extends SQLiteOpenHelper {

    // ...existing methods...

  public static class StudentDetailCursor extends SQLiteCursor {
    /** The query for this cursor */
    private static final String QUERY =
        "SELECT _id, _studentname, _phone, _address, lat, lng, zom FROM students ";
    /** Cursor constructor */
    private StudentDetailCursor(SQLiteDatabase db, SQLiteCursorDriver driver,

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tdd

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Setting up and installing rbenv, ruby-build, rubies, rbenv-gemset, and bundler

This guide enables you to install (ruby-build) and use (rbenv) multiple versions of ruby, isolate project gems (gemsets and/or bundler), and automatically use appropriate combinations of rubies and gems.

TL;DR Demo

# Ensure system is in ship-shape.

aptitude install git zsh libssl-dev zlib1g-dev libreadline-dev libyaml-dev

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If you start to see something like this, e.g. on Heroku since they installed the postgres 9.5 client libraries on their dynos

/usr/lib/postgresql/9.5/bin/pg_dump: invalid option -- 'i'
Try "pg_dump --help" for more information.
rake aborted!
Error dumping database
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.4/lib/active_record/tasks/postgresql_database_tasks.rb:55:in `structure_dump'

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Mac Homebrew (RVM/MySQL/Redis) setup

Follow the steps below to setup a local development environment:

XQuartz

Recommended to download latest XQuartz

iTerm2

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# Doesn't work
	<p>
		<% case @request.author_hosted %>
		<% when "yes" %>
		The school <b>has</b> hosted an author before.
		<% when "no" %>
		The school <b>has not</b> hosted an author before.
		<% end %>
	</p>