Matt Todd mtodd

TAO

Geographically distributed, read-optimized, graph data store.
Favors availability and efficiency over consistency.
Developed by and used within Facebook (social graph).
Link to paper.

Before TAO

Facebook's servers directly accessed MySQL to read/write the social graph.

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

State of emergency in France

Sources

Loi n°55-385 from 1955
Wikipedia / Etat d'urgence en France (general structure)

Process

📂 Persistent "pipes" in Linux

In a project I'm working on I ran into the requirement of having some sort of persistent FIFO buffer or pipe in Linux, i.e. something file-like that could accept writes from a process and persist it to disk until a second process reads (and acknowledges) it. The persistence should be both across process restarts as well as OS restarts.

AFAICT unfortunately in the Linux world such a primitive does not exist (named pipes/FIFOs do not persist

	require 'active_support/all'
	require 'active_record'
	require 'logger'

	ActiveRecord::Base.logger = Logger.new(STDOUT)

	spec = { 'test' => {adapter: 'sqlite3', database: ':memory:'},
	'test_readonly' => {adapter: 'sqlite3', database: ':memory:'},
	'shared_test' => {adapter: 'sqlite3', database: ':memory:'},
	'shared_test_readonly' => {adapter: 'sqlite3', database: ':memory:'}

	require 'rack'

	# Track changes in rack requests and responses made by middleware.
	#
	# SomeMiddleware
	# request: ...
	# response: ...
	# AnotherMiddleware
	# request: ...
	# response: ...

	#![feature(lang_items, asm)]
	#![crate_type = "staticlib"]
	#![no_std]

	const GPIO_BASE: u32 = 0x3F000000;
	const GPIO_SET: u32 = 0x3F200020;
	const GPIO_CLR: u32 = 0x3F20002C;
	const GPIO47: u32 = 0x8000;

	fn sleep(value: u32){

	[
	{
	"city": "Amsterdam",
	"urls": [
	{
	"link": "GVB",
	"url": "http://www.gvb.nl/"
	}
	]
	},

	read () {
	open "http://blitherocher.com"
	}

	article () {

	# change in to the directory where I keep my journal project
	cd /projects/personal_projects/personal_site

	echo "Creating article '$@'"