林煒清(Lin Wei-Ching) superChing

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

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.

I recently switched from using the Evernote Desktop Client to the web client. The only thing I missed was the short-cut for creating Todo checkboxes.

Here is a quick TamperMonkey (Grease Monkey) script to add that functionality back in. Add the userscript to Tampermonkey.

	import scala.util.{Try, Success, Failure}

	def f(s: String): Try[Int] = Try { s.toInt }
	def g(i: Int): Try[Int] = Try { i * 2 }
	def unit[T](v: T): Try[T] = Success(v)

	//val v = "1"
	val v = "bad"
	val m = Success(v)

	#!/usr/bin/env python -O
	#
	# Copyright (c) 2013 Kyle Gorman
	#
	# Permission is hereby granted, free of charge, to any person obtaining a
	# copy of this software and associated documentation files (the
	# "Software"), to deal in the Software without restriction, including
	# without limitation the rights to use, copy, modify, merge, publish,
	# distribute, sublicense, and/or sell copies of the Software, and to
	# permit persons to whom the Software is furnished to do so, subject to

	import play.api.libs.json._
	import play.api.libs.json.Reads._
	// construct a json
	val user = Json.obj("email" -> "[email protected]", "firstName" -> "Foo", "lastName" -> "Bar")


	// > user: play.api.libs.json.JsObject = {"email":"[email protected]","firstName":"Foo","lastName":"Bar"}
	println(s"user -> $user")
	// > user -> {"email":"[email protected]","firstName":"Foo","lastName":"Bar"}

	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<title>Building a router</title>
	<script>
	// Put John's template engine code here...

	(function () {
	// A hash to store our routes:

	// XPath CheatSheet
	// To test XPath in your Chrome Debugger: $x('/html/body')
	// http://www.jittuu.com/2012/2/14/Testing-XPath-In-Chrome/


	// 0. XPath Examples.
	// More: http://xpath.alephzarro.com/content/cheatsheet.html


	'//hr[@class="edge" and position()=1]' // every first hr of 'edge' class

	"""
	A deep neural network with or w/o dropout in one file.

	License: Do What The Fuck You Want to Public License http://www.wtfpl.net/
	"""

	import numpy, theano, sys, math
	from theano import tensor as T
	from theano import shared
	from theano.tensor.shared_randomstreams import RandomStreams

	// PROBLEM STATEMENT

	// Let's build Proxy[T], an object that can capture calls to methods of an underlying object.
	// We want the proxy to be type-safe, i.e. we need to verify that the names of the calls
	// and the arguments that are passed to those calls are well-typed wrt the type of the proxee.

	object Test extends App {
	trait Foo { /* ... */ }
	val proxy: Proxy[Foo] = ???
	proxy.bar()