Pavlo Voznenko pvoznenko

The introduction to Reactive Programming you've been missing

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.

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Description

Display your website availability / performances from Catchpoint® SaaS service.

This using the Catchpoint® Pull API.

Category theory jargon cheat sheet

A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)

I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.

Functor

A functor is something that supports map.

How to go through json object and change values with Circe in Scala

Small gist with some demo trait that shows an example on how to loop through json object and change values with circe in Scala.

Code example you can find below at circe-loop-json-object-example.scala.

The input JSON for test is kinda in in DynamoDB dump format:

	#!/bin/bash

	# Source: http://blog.nonuby.com/blog/2012/07/05/copying-env-vars-from-one-heroku-app-to-another/

	set -e

	sourceApp="$1"
	targetApp="$2"

	while read key value; do

	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.

	import scala.util._
	import java.security.SecureRandom
	import java.security.MessageDigest

	/*
	* Generates a Bearer Token with a length of
	* 32 characters (MD5) or 64 characters (SHA-256) according to the
	* specification RFC6750 (http://tools.ietf.org/html/rfc6750)
	*
	* Uniqueness obtained by hashing system time combined with a

	- What do Etcd, Consul, and Zookeeper do?
	- Service Registration:
	- Host, port number, and sometimes authentication credentials, protocols, versions
	numbers, and/or environment details.
	- Service Discovery:
	- Ability for client application to query the central registry to learn of service location.
	- Consistent and durable general-purpose K/V store across distributed system.
	- Some solutions support this better than others.
	- Based on Paxos or some derivative (i.e. Raft) algorithm to quickly converge to a consistent state.
	- Centralized locking can be based on this K/V store.

	[Unit]
	Description=Service discovery for %i
	After=%i.service
	Requires=%i.service

	[Service]
	Restart=always
	Environment="SLEEP=5"
	Environment="TTL=10"
	Environment='FORMAT="{{ .NetworkSettings.IPAddress }}"'

	#!/usr/bin/env scalas

	/***
	scalaVersion := "2.11.7"
	libraryDependencies += "com.typesafe.play" %% "play-netty-server" % "2.4.6"
	*/

	import play.core.server._
	import play.api.routing.sird._
	import play.api.mvc._