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Thread Pools

Thread pools on the JVM should usually be divided into the following three categories:

1. CPU-bound
2. Blocking IO
3. Non-blocking IO polling

Each of these categories has a different optimal configuration and usage pattern.

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import scala.slick.lifted.CanBeQueryCondition
// optionally filter on a column with a supplied predicate
case class MaybeFilter[X, Y](val query: scala.slick.lifted.Query[X, Y]) {
  def filter[T,R:CanBeQueryCondition](data: Option[T])(f: T => X => R) = {
    data.map(v => MaybeFilter(query.filter(f(v)))).getOrElse(this)
  }
}

// example use case
import java.sql.Date

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Applied Functional Programming with Scala - Notes

Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

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apiVersion: v1
kind: Service
metadata:
  name: redis-service
spec:
  type: LoadBalancer
  selector:
    app: redis
  ports:
    - name: redis

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About

Example on how to run locally an AWS Lambda via API Gateway using localstack.

Based on...

1. https://stackoverflow.com/questions/44547574/create-api-gateway-in-localstack/48682628
2. https://ig.nore.me/2016/03/setting-up-lambda-and-a-gateway-through-the-cli/

Usage

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import java.io.ByteArrayOutputStream
import java.time.Duration
import java.util.concurrent.Executors
import java.util.{Properties, Timer, TimerTask, UUID}

import Models.{Message, SystemMessage, UserMessage, msgAvroSchema}
import com.sksamuel.avro4s.{AvroInputStream, AvroOutputStream, AvroSchema}
import org.apache.kafka.clients.consumer._
import org.apache.kafka.clients.producer._
import org.apache.kafka.common.errors.WakeupException

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How to setup Let's Encrypt for Nginx on Ubuntu 18.04 (including IPv6, HTTP/2 and A+ SLL rating)

---

Virtual hosts

Let's say you want to host domains first.com and second.com.

Create folders for their files:

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How to create an HTTPS certificate for localhost domains

This focuses on generating the certificates for loading local virtual hosts hosted on your computer, for development only.

Do not use self-signed certificates in production ! For online certificates, use Let's Encrypt instead (tutorial).

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package akkahttptest

import akka.http.Http
import akka.stream.ActorFlowMaterializer
import akka.actor.ActorSystem
import akka.stream.scaladsl.{Sink, Source}
import akka.http.model._

object TestClient extends App {

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case class TrieNode[T](edgeList: Map[T, TrieNode[T]] = Map.empty[T, TrieNode[T]], isLeaf: Boolean = false,
                       isEntry: Boolean = false)

object TrieNode {
  def emptyTrieNode[T]: TrieNode[T] = {
    TrieNode[T]()
  }

  def newTrieNode[T](data: T): TrieNode[T] = {
    TrieNode[T](edgeList = Map[T, TrieNode[T]]((data, emptyTrieNode[T])))