jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
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 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

jboner

References from my talk 'Without Resilience, Nothing Else Matters'

• Drift into Failure
• How Complex Systems Fail
• Antifragile: Things That Gain from Disorder
• Leverage Points: Places to Intervene in a System
• Going Solid: A Model of System Dynamics and Consequences for Patient Safety
• Resilience in Complex Adaptive Systems: Operating at the Edge of Failure
• Puppies! Now that I’ve got your attention, Complexity Theory
• [Towards Resilient Architectures: Biology

jboner

package sample.eventdriven.scala

import akka.actor.{Actor, ActorRef, ActorSystem, Inbox, Props}
import akka.persistence.PersistentActor

import scala.concurrent.ExecutionContext.Implicits._
import scala.concurrent.duration._

// ===============================================================
// Demo of an Event-driven Architecture in Akka and Scala.

jboner

Transactors: Actors + STM

Actors are excellent for solving of problems where you have many independent processes 
that can work in isolation and only interact with other Actors through message passing. 
This model fits many problems. But the actor model is unfortunately a terrible model for 
implementing truly shared state. E.g. when you need to have consensus and a stable view of 
state across many components. The classic example is the bank account to clients to 
deposits and withdrawals in which each operation needs to be atomic. For detailed 
discussion on the topic see this JavaOne presentation: 
http://www.slideshare.net/jboner/state-youre-doing-it-wrong-javaone-2009.

jboner

/*
Copyright 2012 Twitter, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software

jboner

VS Code Plugins and configuration tips

https://code.visualstudio.com/docs/setup/setup-overview

Plugins

• Project manager https://marketplace.visualstudio.com/items?itemName=alefragnani.project-manager
• Scala metals https://marketplace.visualstudio.com/items?itemName=scalameta.metals

jboner

Akka Cluster Implementation Notes

Slightly disorganized but reasonably complete notes on the algorithms, strategies and optimizations of the Akka Cluster implementation. Could use a lot more links and context etc., but was just written for my own understanding. Might be expanded later.

Links to papers and talks that have inspired the implementation can be found on the 10 last pages of this presentation.

Akka Gossip

Gossip state

This is the Gossip state representation:

jboner

Typesafe Project & Developer Guidelines

These guidelines are meant to be a living document that should be changed and adapted as needed. We encourage changes that makes it easier to achieve our goals in an efficient way.

These guidelines mainly applies to Typesafe’s “mature” projects - not necessarily to projects of the type ‘collection of scripts’ etc.

General Workflow

This is the process for committing code into master. There are of course exceptions to these rules, for example minor changes to comments and documentation, fixing a broken build etc.

jboner

# How Akka maps to EAI Patterns

Might be up for debate or just plain wrong. Just some notes I scribbled down some time ago. 

-----------------------------------------------------------------------------------------------------------------
EAI PATTERN                     AKKA PATTERN                  REFERENCE
-----------------------------------------------------------------------------------------------------------------
Point to Point Channel          Regular Actor Communication   http://www.eaipatterns.com/PointToPointChannel.html
Event-Driven Consumer           Regular Actor Receive         http://www.eaipatterns.com/EventDrivenConsumer.html
Message Selector                Actor with Stash              http://www.eaipatterns.com/MessageSelector.html

jboner

package sample.eventdriven.java;

import akka.actor.*;
import akka.persistence.AbstractPersistentActor;
import scala.concurrent.duration.Duration;

import java.io.Serializable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;