TrainTravel

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

---

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

---

TrainTravel

Start your rethinkdb instance with this flag: --bind all (or bind=all in the configuration file for your instance)

Block external access to the web UI with these two commands: sudo iptables -A INPUT -i eth0 -p tcp --dport 8080 -j DROP sudo iptables -I INPUT -i eth0 -s 127.0.0.1 -p tcp --dport 8080 -j ACCEPT

Install nginx: sudo apt-get install nginx

TrainTravel

#include"SingleCoreSolution.h"
namespace SingleCoreSolution {
	std::string Solution::TrickOrTreat(const std::vector<int>& pieces,
		const int homes, const int max) {

		//calculate prefix sum;
		std::vector<int> prefixSum(homes + 1, 0);
		for (int i = 0; i < homes; ++i) {
			prefixSum[i + 1] = prefixSum[i] + pieces[i];
		}

TrainTravel

Serialization

As all objects must be Serializable to be used as part of RDD operations in Spark, it can be difficult to work with libraries which do not implement these featuers.

Java Solutions

Simple Classes

For simple classes, it is easiest to make a wrapper interface that extends Serializable. This means that even though UnserializableObject cannot be serialized we can pass in the following object without any issue

public interface UnserializableWrapper extends Serializable {
 public UnserializableObject create(String parm1, String parm2);

TrainTravel

import java.time.{LocalDate, LocalDateTime, LocalTime}

/*case */class FullName(val first: String, val last: String)

object FullName {
  def apply(first: String, last: String): FullName =
    new FullName(first, last)

  def unapply(full: FullName): Some[(String, String)] =
    Some((full.first, full.last))

TrainTravel

Recursion and Trampolines in Scala

Recursion is beautiful. As an example, let's consider this perfectly acceptable example of defining the functions even and odd in Scala, whose semantics you can guess:

def even(i: Int): Boolean = i match {
  case 0 => true
  case _ => odd(i - 1)
}

def odd(i: Int): Boolean = i match {

TrainTravel

rednaxelafx@fx-laptop:~$ jps
7013 Jps
6946 GroovyStarter
rednaxelafx@fx-laptop:~$ cd /proc/6946
rednaxelafx@fx-laptop:/proc/6946$ ls
attr             cpuset   latency    mountstats   root       statm
auxv             cwd      limits     net          sched      status
cgroup           environ  loginuid   numa_maps    schedstat  syscall
clear_refs       exe      maps       oom_adj      sessionid  task
cmdline          fd       mem        oom_score    smaps      wchan

TrainTravel

package bbejeck.grouping

import org.apache.log4j.{Level, Logger}
import org.apache.spark.{SparkConf, SparkContext}

import scala.collection.mutable

/**
 * Created by bbejeck on 7/31/15.
 *

TrainTravel

sealed trait Option[+A]
case object None extends Option[Nothing]
case class Some[A](a: A) extends Option[A]

object ProductType {
  type TwoBooleansOrNone = Option[(Boolean, Boolean)]

  def mustBeBothTrue(in: TwoBooleansOrNone): Boolean = in match {
    case None => false
    case Some((true, true)) => true

TrainTravel

class UserManagerLifecycleTest
    extends ScalaTestWithActorTestKit
    with AnyWordSpecLike {
  implicit val dynamoClient: DynamoDbAsyncClient =
    new DynamoDbAsyncClient {
      override def serviceName(): String = "test"

      override def close(): Unit = ()
    }
  implicit val ec: ExecutionContext =