Vitor Vieira vitorsvieira

Internet Scale Services Checklist

A checklist for designing and developing internet scale services, inspired by James Hamilton's 2007 paper "On Desgining and Deploying Internet-Scale Services."

http://mvdirona.com/jrh/talksandpapers/jamesrh_lisa.pdf

Basic tenets

Does the design expect failures to happen regularly and handle them gracefully?
Have we kept things as simple as possible?

Scala macros tutorial, using sbt

The following steps executed in order will;

create the project file structure
set the sbt version
add the gen-idea sbt plugin (if you want to import your project into intellij)
create an sbt build, that builds the macros project prior to the macrostest project (so the regex macro is usable in the macrostest project)
create the macros project scala file
create the macrostest project scala file

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

	{-# LANGUAGE NoMonomorphismRestriction #-}
	{-# LANGUAGE TemplateHaskell #-}
	{-# OPTIONS_GHC -fwarn-missing-methods #-}
	module Err where

	import Control.Lens
	import Control.Monad.Error
	import Control.Monad.Error.Lens

	-- Here is a fairly typical situation, where we have low level errors in certain

	import scala.concurrent.duration._
	import scala.concurrent.ExecutionContext
	import scala.concurrent.Future
	import akka.pattern.after
	import akka.actor.Scheduler

	/**
	* Given an operation that produces a T, returns a Future containing the result of T, unless an exception is thrown,
	* in which case the operation will be retried after _delay_ time, if there are more possible retries, which is configured through
	* the _retries_ parameter. If the operation does not succeed and there is no retries left, the resulting Future will contain the last failure.

	def getValMacro(c: Context)(s: c.Expr[Any]) : c.Expr[Any] = {
	import c.universe._
	val q"val $name = $value" = s.tree
	c.Expr(value)
	}

	def getVal(s: Any) = macro getValMacro

	getVal{val x = 17}
	error: exception during macro expansion: