Oğulcan Girginç ogirginc

Originally published in June 2008

When hiring Ruby on Rails programmers, knowing the right questions to ask during an interview was a real challenge for me at first. In 30 minutes or less, it's difficult to get a solid read on a candidate's skill set without looking at code they've previously written. And in the corporate/enterprise world, I often don't have access to their previous work.

To ensure we hired competent ruby developers at my last job, I created a list of 15 ruby questions -- a ruby measuring stick if you will -- to select the cream of the crop that walked through our doors.

What to expect

Candidates will typically give you a range of responses based on their experience and personality. So it's up to you to decide the correctness of their answer.

Grab new backup of database

Command: heroku pgbackups:capture --remote production

Response: >>> HEROKU_POSTGRESQL_COLOR_URL (DATABASE_URL) ----backup---> a712

Get url of backup download

Command: heroku pgbackups:url [db_key] --remote production

Make it real

Ideas are cheap. Make a prototype, sketch a CLI session, draw a wireframe. Discuss around concrete examples, not hand-waving abstractions. Don't say you did something, provide a URL that proves it.

Ship it

Nothing is real until it's being used by a real user. This doesn't mean you make a prototype in the morning and blog about it in the evening. It means you find one person you believe your product will help and try to get them to use it.

Do it with style

Capybara Actions

# Anchor
click_link 'Save'

# Button
click_button 'awesome'

# Both above

Turning PostgreSQL into a queue serving 10,000 jobs per second

RDBMS-based job queues have been criticized recently for being unable to handle heavy loads. And they deserve it, to some extent, because the queries used to safely lock a job have been pretty hairy. SELECT FOR UPDATE followed by an UPDATE works fine at first, but then you add more workers, and each is trying to SELECT FOR UPDATE the same row (and maybe throwing NOWAIT in there, then catching the errors and retrying), and things slow down.

On top of that, they have to actually update the row to mark it as locked, so the rest of your workers are sitting there waiting while one of them propagates its lock to disk (and the disks of however many servers you're replicating to). QueueClassic got some mileage out of the novel idea of randomly picking a row near the front of the queue to lock, but I can't still seem to get more than an an extra few hundred jobs per second out of it under heavy load.

So, many developers have started going straight t

	Backtrace generated 500 times with 1508 frames
	Thread ID: 69872793616820
	Total Time: 0.377622164
	Sort by: total_time

	%total %self total self wait child calls Name
	--------------------------------------------------------------------------------
	100.00% 0.01% 0.378 0.000 0.000 0.378 1 Global#[No method]
	0.378 0.000 0.000 0.378 1/301 Object#one
	--------------------------------------------------------------------------------

	select.form-control + .chosen-container.chosen-container-single .chosen-single {
	display: block;
	width: 100%;
	height: 34px;
	padding: 6px 12px;
	font-size: 14px;
	line-height: 1.428571429;
	color: #555;
	vertical-align: middle;
	background-color: #fff;

	# 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 names based on the keys in <tt>filtering_params</tt>
	# with their associated values. For example, "{ status: 'delayed' }" would call