Abhijit Pratap Singh abhijitiitr

Codemesh 2014, London

keynote: complexity is outside the code

@jessitron and @tastapod
slides

when I started programming:

architecture was always:
- box - box - cylinder
then layers:
- ideally:

On the Viability of Erlang Releases and CouchDB

There has been some discussion on what versions of Erlang CouchDB should support, and what versions of Erlang are detrimental to use. Sadly there were some pretty substantial problems in the R15 line and even parts of R16 that are landmines for CouchDB. This post will describe the current state of things and make some potential recommendations on approach.

Scheduler Collapse

A quick "how to" on what you need to do to both setup AND recover a single-server PostgreSQL database using WAL-E

WAL-E: https://github.com/wal-e/wal-e
Assuming Ubuntu 12.04 LTS ("Precise")
We'll be using S3. Make sure you have an IAM in a group with GetObject, ListBucket and PutObject on the bucket you want to use (and that it's not public).

Setup:

These packages:

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns                     on recent CPU
L2 cache reference ........................... 7 ns                     14x L1 cache
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns                     20x L2 cache, 200x L1 cache
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 4X memory

Overview

There are lots of representations for strings. In most languages they pick one set of tradeoffs and run with it. In haskell the "default" implementation (at least the one in the prelude) is a pretty bad choice, but unlike most other languages (really) good implementations exist for pretty much every way you can twist these things. This can be a good thing, but it also leads to confusion, and frustration to find the right types and how to convert them.

	nginx/
	!nginx/.gitkeep
	!nginx/logs/.gitkeep

	src/

	tmp/

	# Run with: rake environment elasticsearch:reindex

	namespace :elasticsearch do
	desc "re-index elasticsearch"
	task :reindex => :environment do

	klass = Place
	ENV['CLASS'] = klass.name
	ENV['INDEX'] = new_index = klass.tire.index.name << '_' << Time.now.strftime('%Y%m%d%H%M%S')

	#!/bin/bash

	gdb -p "$1" -batch -ex 'set {short}$rip = 0x050f' -ex 'set $rax=231' -ex 'set $rdi=0' -ex 'cont'