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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

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Update May 2017

Eric Bidelman has documented some of the common workflows possible with headless Chrome over in https://developers.google.com/web/updates/2017/04/headless-chrome.

Update

If you're looking at this in 2016 and beyond, I strongly recommend investigating real headless Chrome: https://chromium.googlesource.com/chromium/src/+/lkgr/headless/README.md

Windows and Mac users might find using Justin Ribeiro's Docker setup useful here while full support for these platforms is being worked out.

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JavaScript Crypto Libraries

I start with a list and plan to create a comparison table.

WebCryptoAPI

http://www.w3.org/TR/WebCryptoAPI/

This specification describes a JavaScript API for performing basic cryptographic operations in web applications, such as hashing, signature generation and verification, and encryption and decryption. Additionally, it describes an API for applications to generate and/or manage the keying material necessary to perform these operations. Uses for this API range from user or service authentication, document or code signing, and the confidentiality and integrity of communications.

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#Introduction

Developing Chrome Extensions is REALLY fun if you are a Front End engineer. If you, however, struggle with visualizing the architecture of an application, then developing a Chrome Extension is going to bite your butt multiple times due the amount of excessive components the extension works with. Here are some pointers in how to start, what problems I encounter and how to avoid them.

Note: I'm not covering chrome package apps, which although similar, work in a different way. I also won't cover the page options api neither the new brand event pages. What I explain covers most basic chrome applications and should be enough to get you started.

Table of Contents

1. Understand the Chrome Architecture
2. Understand the Tabs-Extension Relationship
3. Picking the right interface for the job

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/**
 * A generic confirmation for risky actions.
 * Usage: Add attributes: ng-really-message="Are you sure"? ng-really-click="takeAction()" function
 */
angular.module('app').directive('ngReallyClick', [function() {
    return {
        restrict: 'A',
        link: function(scope, element, attrs) {
            element.bind('click', function() {
                var message = attrs.ngReallyMessage;

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html,body {
  height: 100%;
  background: blue;
}

.fill-div {
  height: 100%;
  width: 100%
}

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// Use Gists to store code you would like to remember later on
console.log(window); // log the "window" object to the console

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//
//  Badge.swift
//  Extensions for Rounded UILabel and UIButton, Badged UIBarButtonItem.
//
//  Created by Yonat Sharon on 06.04.2015.
//  Copyright (c) 2015 Yonat Sharon. All rights reserved.
//

import UIKit

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require 'benchmark'

class Proc
  def slow_callback(callable, *args)
    self === Class.new do
      method_name = callable.to_sym
      define_method(method_name) { |&block| block.nil? ? true : block.call(*args) }
      define_method("#{method_name}?") { true }
      def method_missing(method_name, *args, &block) false; end
    end.new

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import UIKit

protocol YelpRequestDelegate {
    func getYelpData() -> AnyObject
    func processYelpData(data: NSData) -> NSData
}

class YelpAPI {
    var delegate: YelpRequestDelegate?