Ju soasme

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Introduction

At DICOM Grid, we recently made the decision to use Haskell for some of our newer projects, mostly small, independent web services. This isn't the first time I've had the opportunity to use Haskell at work - I had previously used Haskell to write tools to automate some processes like generation of documentation for TypeScript code - but this is the first time we will be deploying Haskell code into production.

Over the past few months, I have been working on two Haskell services:

A reimplementation of an existing socket.io service, previously written for NodeJS using TypeScript.
A new service, which would interact with third-party components using standard data formats from the medical industry.

I will write here mostly about the first project, since it is a self-contained project which provides a good example of the power of Haskell. Moreover, the proces

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	Ansible playbook to setup HTTPS using Let's encrypt on nginx.

	The Ansible playbook installs everything needed to serve static files from a nginx server over HTTPS.
	The server pass A rating on [SSL Labs](https://www.ssllabs.com/).

	To use:
	1. Install [Ansible](https://www.ansible.com/)
	2. Setup an Ubuntu 16.04 server accessible over ssh
	3. Create `/etc/ansible/hosts` according to template below and change example.com to your domain
	4. Copy the rest of the files to an empty directory (`playbook.yml` in the root of that folder and the rest in the `templates` subfolder)

	# Simple sample of LIBFFI usage in pypy/rpython

	import sys
	from rpython.rtyper.lltypesystem import rffi, lltype
	from rpython.rlib import jit_libffi, rdynload, clibffi

	def entry_point(argv):
	lib = rdynload.dlopen('libSDL.so')
	SDL_Init = rdynload.dlsym(lib, "SDL_Init")

	BUILD_VER=2.7.13

	mkdir download /tmp/installdir; cd download;
	curl -LO http://python.org/ftp/python/${BUILD_VER}/Python-${BUILD_VER}.tgz

	tar xf Python-${BUILD_VER}.tgz
	cd Python-${BUILD_VER}

	# install build deps
	yum -y install openssl-devel readline-devel bzip2-devel sqlite-devel zlib-devel ncurses-devel db4-devel expat-devel gdbm-devel

	# taken from http://www.piware.de/2011/01/creating-an-https-server-in-python/
	# generate server.xml with the following command:
	# openssl req -new -x509 -keyout server.pem -out server.pem -days 365 -nodes
	# run as follows:
	# python simple-https-server.py
	# then in your browser, visit:
	# https://localhost:4443

	import BaseHTTPServer, SimpleHTTPServer
	import ssl

	TMP_PATH=~/tmp_install_python

	# Versions section
	PYTHON_MAJOR=2.7
	PYTHON_VERSION=$PYTHON_MAJOR.10

	mkdir $TMP_PATH && cd $TMP_PATH

	# Update yum and libraries
	yum -y update

	if(a>=b) and else
	assume input array is like this

	0 1 0 A B 0
	and we are pointing to A

	+>+<[->-[>]<<]<[- BLOCK_A_GE_B]<[-< BLOCK_A_LT_B ]

	import os
	import asyncio
	import sys

	from asyncio.streams import StreamWriter, FlowControlMixin

	reader, writer = None, None

	@asyncio.coroutine
	def stdio(loop=None):