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.

djspiewak

Explaining Miles's Magic

Miles Sabin recently opened a pull request fixing the infamous SI-2712. First off, this is remarkable and, if merged, will make everyone's life enormously easier. This is a bug that a lot of people hit often without even realizing it, and they just assume that either they did something wrong or the compiler is broken in some weird way. It is especially common for users of scalaz or cats.

But that's not what I wanted to write about. What I want to write about is the exact semantics of Miles's fix, because it does impose some very specific assumptions about the way that type constructors work, and understanding those assumptions is the key to getting the most of it his fix.

For starters, here is the sort of thing that SI-2712 affects:

def foo[F[_], A](fa: F[A]): String = fa.toString

przemek-pokrywka

#!/bin/bash
test -e ~/.coursier/cr || (mkdir -p ~/.coursier && wget -q -O ~/.coursier/cr https://git.io/vgvpD && chmod +x ~/.coursier/cr)
CLASSPATH="$(~/.coursier/cr fetch -q -p \
  \
  com.typesafe.play:play-netty-server_2.11:2.5.0 \
  com.typesafe.play:play_2.11:2.5.0 \
  com.lihaoyi:ammonite-repl_2.11.7:0.5.2 \
  \
)" java \
  -Dplay.crypto.secret=foo.bar.baz \

fiadliel

import com.ning.http.client._
import com.typesafe.scalalogging.StrictLogging
import scodec.bits.ByteVector

import scala.concurrent.duration._
import scalaz._
import scalaz.Scalaz._
import scalaz.concurrent.Task
import scalaz.stream._

DomBlack

import akka.stream.scaladsl.Flow

import scala.concurrent.{ ExecutionContext, Future }
import scalaz._
import scalaz.std.scalaFuture.futureInstance // IntelliJ lies

/**
 * Flowz provides Akka Stream Flow like methods for monadic types.
 *
 * You can define the `M` type and the input type, and let the compiler infer the output

stefanobaghino

package controllers

import java.util.Properties

import com.typesafe.config.ConfigFactory
import kafka.consumer.{Consumer, ConsumerConfig, ConsumerConnector, Whitelist}
import kafka.serializer.StringDecoder
import play.api.libs.iteratee.{Enumerator, Iteratee}
import play.api.mvc.{Controller, WebSocket}

travisbrown

import scala.language.experimental.macros
import scala.reflect.macros.whitebox

class FreeMacros(val c: whitebox.Context) {
  import c.universe._

  def smartName(name: String): String = (
    name.toList match {
      case h :: t => h.toLower :: t
      case Nil => Nil

Fristi

package nl.mdj.fpinscala

import java.net.InetSocketAddress
import java.nio.channels.AsynchronousChannelGroup
import java.util.concurrent.atomic.AtomicInteger

import scodec.bits.ByteVector

import scala.annotation.tailrec
import scalaz.netty.Netty

jamesthompson

// This should work with Scala 2.10.4 & scalaz 7.1, core, effect and concurrent packages
import scalaz.{ concurrent, Free, Functor, Monad, syntax }
import concurrent.Task
import Free.{freeMonad => _, _}
import syntax.monad._

// Describe the set of actions - which are functors

sealed trait RedisF[+A] {
  def map[B](fn: A => B): RedisF[B]

jimmycuadra

#cloud-config

coreos:
  etcd:
    # generate a new token for each unique cluster from https://discovery.etcd.io/new
    discovery: https://discovery.etcd.io/<token>
    # multi-region deployments, multi-cloud deployments, and droplets without
    # private networking need to use $public_ipv4
    addr: $private_ipv4:4001
    peer-addr: $private_ipv4:7001