Tomek Wałkuski tomekw

If you have two days to learn the very basics of modelling, Domain-Driven Design, CQRS and Event Sourcing, here's what you should do:

In the evenings read the [Domain-Driven Design Quickly Minibook]{http://www.infoq.com/minibooks/domain-driven-design-quickly}. During the day watch following great videos (in this order):

Eric Evans' [What I've learned about DDD since the book]{http://www.infoq.com/presentations/ddd-eric-evans}
Eric Evans' [Strategic Design - Responsibility Traps]{http://www.infoq.com/presentations/design-strategic-eric-evans}
Udi Dahan's [Avoid a Failed SOA: Business & Autonomous Components to the Rescue]{http://www.infoq.com/presentations/SOA-Business-Autonomous-Components}
Udi Dahan's [Command-Query Responsibility Segregation]{http://www.infoq.com/presentations/Command-Query-Responsibility-Segregation}
Greg Young's [Unshackle Your Domain]{http://www.infoq.com/presentations/greg-young-unshackle-qcon08}
Eric Evans' [Acknowledging CAP at the Root -- in the Domain Model]{ht

Make it real

Ideas are cheap. Make a prototype, sketch a CLI session, draw a wireframe. Discuss around concrete examples, not hand-waving abstractions. Don't say you did something, provide a URL that proves it.

Ship it

Nothing is real until it's being used by a real user. This doesn't mean you make a prototype in the morning and blog about it in the evening. It means you find one person you believe your product will help and try to get them to use it.

Do it with style

"Russian-Doll Caching" is great. It embraces the Rails (and Ruby) goal to "make the developer happy". And it does. Not having to worry about cache expiration is superb.

It has its limits, though. If you're trying to avoid any database queries, russian-doll caching will not work for you. If you are trying to represent thousands, or even hundreds, of objects under a single cache fragment, russian-doll caching is not the best option.

We use it whenever it makes sense, but sometimes we just have to bite the bullet and expire a cache fragment manually. When you want to start manually expiring cache on a fairly busy website, you have to start considering race conditions. I recently ran into the following scenario:

class Post < ActiveRecord::Base
  after_save :expire_cache

This runs a build for a small elixir (phoenix) project in about 40 seconds by caching as much of the compiled files as possible.

We've been using this for months in multiple projects without any issues. Please ping be if there is any issues with this script and I'll update it.

It should be generic enough to work on any elixir app using mix.

If you have a elixir_buildpack.config, then enable that section in the build script to keep versions in sync!

2016-08-09: Updated to newer Erlang and Elixir and fixed curl command.

Using OTP's observer (appmon replacement) remotely

$ ssh remote-host "epmd -names"
epmd: up and running on port 4369 with data:
name some_node at port 58769

Note the running on port for epmd itself and the port of the node you're interested in debugging. Reconnect to the remote host with these ports forwarded:

$ ssh -L 4369:localhost:4369 -L 58769:localhost:58769 remote-host

Freenode IRC

Connect

/server chat.freenode.net

Nick

Thread Pools

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

CPU-bound
Blocking IO
Non-blocking IO polling

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

	defmodule MyApp do
	use Application

	def start(_type, _args) do
	import Supervisor.Spec, warn: false

	children = [
	Plug.Adapters.Cowboy.child_spec(:http, MyApp.Router, [], [
	dispatch: dispatch
	])

	SPC
	SPC: find file
	, switch buffer
	. browse files
	: MX
	; EX
	< switch buffer
	` eval
	u universal arg
	x pop up scratch

	{:aliases
	{:dev {:extra-deps {com.bhauman/rebel-readline {:mvn/version "0.1.2"}
	org.clojure/tools.nrepl {:mvn/version "0.2.12"}
	cider/cider-nrepl {:mvn/version "0.17.0-SNAPSHOT"}}
	:main-opts ["-m" "repl"]}}}