djspiewak

Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea

yossorion

What I Wish I'd Known About Equity Before Joining A Unicorn

Disclaimer: This piece is written anonymously. The names of a few particular companies are mentioned, but as common examples only.

This is a short write-up on things that I wish I'd known and considered before joining a private company (aka startup, aka unicorn in some cases). I'm not trying to make the case that you should never join a private company, but the power imbalance between founder and employee is extreme, and that potential candidates would

leohacker

Everything I Ever Learned About JVM Performance Tuning @Twitter- by Attila Szegedi
http://www.infoq.com/presentations/JVM-Performance-Tuning-twitter (video & slides)
  
9 Fallacies of Java Performance - by Ben Evans
http://www.infoq.com/articles/9_Fallacies_Java_Performance (video & slides)
 
Visualizing Java GC - by Ben Evans
http://www.infoq.com/presentations/Visualizing-Java-GC (video & slides)
 
 

milessabin

scala> class Foo { self: Singleton => }
defined class Foo

scala> class Bar extends Foo
<console>:12: error: illegal inheritance;
 self-type Bar does not conform to Foo's selftype Foo with Singleton
       class Bar extends Foo
                         ^

scala> object Bar extends Foo

rahilb

-- an openresty/nginx authenticator that checks bearer tokens with
-- an ID service for use with `access_by_lua_file` nginx directive

local http = require "resty.http"
local hc = http:new()

function abandon_request(status_code, response_body)
    ngx.header["WWW-Authenticate"] = "Bearer"
    ngx.status = status_code
    ngx.say(response_body)

colestanfield

// Create a new MergeStrategy for aop.xml files
val aopMerge: MergeStrategy = new MergeStrategy {
  val name = "aopMerge"
  import scala.xml._
  import scala.xml.dtd._

  def apply(tempDir: File, path: String, files: Seq[File]): Either[String, Seq[(File, String)]] = {
    val dt = DocType("aspectj", PublicID("-//AspectJ//DTD//EN", "http://www.eclipse.org/aspectj/dtd/aspectj.dtd"), Nil)
    val file = MergeStrategy.createMergeTarget(tempDir, path)

danehammer

import backtype.storm.generated.Grouping;
import backtype.storm.hooks.BaseTaskHook;
import backtype.storm.hooks.info.BoltAckInfo;
import backtype.storm.hooks.info.EmitInfo;
import backtype.storm.task.TopologyContext;

import java.util.Map;
import java.util.concurrent.TimeUnit;

import com.google.common.collect.ArrayListMultimap;

byllc

###IF you are using Raspian many of these tasks are unescessary. With Raspbian:

• SSH is ready to go out of the box
• default runlevel is 3
• many items can be configured with raspi-config tool

###Adding more swap for high memory use concerns

  sudo dd if=/dev/zero of=/swap bs=1M count=1024
  sudo mkswap /swap
  sudo swapon /swap

mrflip

Tuning Storm+Trident

Tuning a dataflow system is easy:

The First Rule of Dataflow Tuning:
* Ensure each stage is always ready to accept records, and
* Deliver each processed record promptly to its destination

patriknw

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package akka.contrib.mailbox

import scala.concurrent.duration._
import java.util.concurrent.atomic.AtomicInteger
import java.util.concurrent.atomic.AtomicLong
import com.typesafe.config.Config
import akka.actor.{ ActorContext, ActorRef, ActorSystem, ExtendedActorSystem }