melvic-ybanez

Request Validation with Akka-HTTP and Cats

Greg Beech wrote an article on Akka HTTP Entity Validation. This post is on the same topic, except we are going to use typeclass instances, as opposed to subtyping, for form validations.

Sample Problem: User Regsitration

To start with, let us suppose that we are working on some sort of user management service using Scala/Akka. However, here we are only going to focus on the registration part, in which the client is expected to send a user data, in JSON format; and the server needs to validate them, and save the user if the validations succeed, or reject the request with all the errors detected. That said, we should keep in mind that our validations may be used through out the entire codebase, not just in the user registration endpoint.

The rules for our validation are as follows:

emesday

import scala.reflect.ClassTag
import scala.util.Random

class Reservoir[T: ClassTag](
  private val size: Int,
  private val seed: Long = Random.nextLong()) extends Serializable {

  private val rand = new Random(seed)
  private val reservoir = new Array[T](size)
  private var count = 0L

laughedelic

Some of these practices might be based on wrong assumptions and I'm not aware of it, so I would appreciate any feedback.

1. avoiding some dependency conflicts:

   • install sbt-explicit-dependencies globally in your ~/.sbt/{0.13,1.0}/plugins/plugins.sbt
   • run undeclaredCompileDependencies and make the obvious missing dependencies explicit by adding them to libraryDependencies of each sub-project
   • (optionally) run unusedCompileDependencies and remove some obvious unused libraries. This has false positives, so ; reload; Test/compile after each change and ultimately run all tests to see that it didn't break anything
   • (optionally) add undeclaredCompileDependenciesTest to the CI pipeline, so that it will fail if you have some undeclared dependencies

2. keeping dependencies up to date and resolving conflicts:

   • install sbt-updates globally in your `~/.sbt/{0.13,1.0}/plugins/plugins.

eddies

class ApacheSpark < Formula
  desc "Engine for large-scale data processing"
  homepage "https://spark.apache.org/"
  url "https://archive.apache.org/dist/spark/spark-2.2.0/spark-2.2.0-bin-hadoop2.7.tgz"
  version "2.2.0"
  sha256 "97fd2cc58e08975d9c4e4ffa8d7f8012c0ac2792bcd9945ce2a561cf937aebcc"
  head "https://github.com/apache/spark.git"

  bottle :unneeded

chrismccord

Phoenix 1.4 ships with exciting new features, most notably with HTTP2 support, improved development experience with faster compile times, new error pages, and local SSL certificate generation. Additionally, our channel layer internals receiveced an overhaul, provided better structure and extensibility. We also shipped a new and improved Presence javascript API, as well as Elixir formatter integration for our routing and test DSLs.

This release requires few user-facing changes and should be a fast upgrade for those on Phoenix 1.3.x.

Install the new phx.new project generator

The mix phx.new archive can now be installed via hex, for a simpler, versioned installation experience.

To grab the new archive, simply run:

Daenyth

Operation	Input	Result	Notes
map	F[A] , A => B	F[B]	Functor
apply	F[A] , F[A => B]	F[B]	Applicative
(fa, fb, ...).mapN	(F[A], F[B], ...) , (A, B, ...) => C	F[C]	Applicative
(fa, fb, ...).tupled	(F[A], F[B], ...)	F[(A, B, ...)]	Applicative
flatMap	F[A] , A => F[B]	F[B]	Monad
traverse	F[A] , A => G[B]	G[F[A]]	Traversable; fa.traverse(f) == fa.map(f).sequence; "foreach with effects"
sequence	F[G[A]]	G[F[A]]	Same as fga.traverse(identity)
attempt	F[A]	F[Either[E, A]]	Given ApplicativeError[F, E]

chriswhong

// custom mapbopx-gl-draw mode that modifies draw_line_string
// shows a center point, radius line, and circle polygon while drawing
// forces draw.create on creation of second vertex

import MapboxDraw from 'mapbox-gl-draw';
import numeral from 'numeral';
import lineDistance from 'npm:@turf/line-distance';

const RadiusMode = MapboxDraw.modes.draw_line_string;

jpbecotte

Introduction

I have been struggling to start a new project with Phoenix 1.3 and the new vue-cli 3 for Vue.js. There are tons of example already but none of them suited my needs, because:

• I want to use the new Vue-cli to select the features that I want,
• I do NOT want to setup Webpack (I know, what a shame!). The new Vue-cli includes the new vue-cli-service, which uses an instance of webpack-dev-server, so you don't have to import it manually in your project.
• I do not want to use Brunch.

Create your Phoenix App

Assuming that you have Elixir and Phoenix 1.3 are both installed, let's build our new App.

djspiewak

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.

crittermike

# One liner
wget --recursive --page-requisites --adjust-extension --span-hosts --convert-links --restrict-file-names=windows --domains yoursite.com --no-parent yoursite.com

# Explained
wget \
     --recursive \ # Download the whole site.
     --page-requisites \ # Get all assets/elements (CSS/JS/images).
     --adjust-extension \ # Save files with .html on the end.
     --span-hosts \ # Include necessary assets from offsite as well.
     --convert-links \ # Update links to still work in the static version.