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import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

public class CallbackB {

    /**

ammachado

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:

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# 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

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import java.util.zip._
import java.io._

class InMemZip(compressionLevel: Int) {
  private val _outBytes = new ByteArrayOutputStream
  private val _zipOutStream = {
    val s = new ZipOutputStream(_outBytes)
    s.setLevel(compressionLevel)
    s
  }

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import java.util.Formatter;

public class Bytes2Hex {
    public static String byteToHex(final byte[] hash) {
        try (final Formatter formatter = new Formatter()) {
            for (byte b : hash)
                formatter.format("%02x", b);
            return formatter.toString();
        }
    }

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class ClusterMetricsElasticScaleListener extends Actor with ActorLogging {
  val selfAddress = Cluster(context.system).selfAddress

  override def preStart(): Unit =
    Cluster(context.system).subscribe(self, classOf[ClusterMetricsChanged])

  override def postStop(): Unit =
    Cluster(context.system).unsubscribe(self)

  def receive = {

ammachado

import scala.language.postfixOps
import scala.concurrent._
import scala.concurrent.duration._
import akka.pattern.pipe
import akka.actor._
import akka.cluster.routing._
 
/**
 * Concept and some code lifted from
 * https://github.com/jsuereth/intro-to-fp, thanks Josh!

ammachado

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

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// An ADT+shapeless as a drop-in replacement for a standard Scala Enumeration.
//
// First the unsafe standard Scala Enumeration ...
//
object ScalaEnumDemo extends App {
  // Example from scala.Enumeration scaladoc. Terse ...
  object WeekDay extends Enumeration {
    type WeekDay = Value
    val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
  }

ammachado

Intro

To view the progress of a Powerpoint presentation, a progress bar can be displayed at the bottom of the slide show.

How to proceed

Once the slideshow is complete, go to Tools > Macro > Visual Basic Editor.

In the new window, select Insert > Module and copy this text in the blank page:

Sub AddProgressBar()
    On Error Resume Next