Painful parts

Mutability​/IMpurity

• You can reopen classes
• You can include modules
• You can define callbacks
• Static variables

Hard to follow / resonate about code. Older the system, worse it is.

Painful parts

Concurrency (lack of)

• Ruby is slow
• It's a pain to manage threads
• Usage of background jobs as a workaround

We more and more need to talk with different APIs to find the best result for the customer.

It's really hard to do it in a safe and concurrent way.

Painful parts

ActiveRecord (ORM)

• High coupling between business and DB
• DB queries/commands triggered implicitly
• Slow tests

Database available everywhere

Solutions?

Golang​

+ concurrency

+ speed

Wasn't convinced at all. It was really fast but all the rest: code, community mindset, Go principles didn't match with me

 - code readability

 - lack of generics

Solutions?

Erlang​

+ concurrency

+ speed

+ immutability

Was totally convinced but I tried to read some book and no way to understand how it really worked / how to use it

 - syntax

 - learning curve

Solutions?

Elixir​

+  concurrency

+  speed

+  immutability

Was really convinced but was a bit worried about the fact it was really young.

+  syntax

±  learning curve

± really young

Erlang

History​

• Old language (1986)
• Created by Ericsson
• Aim of improving the development of telephony applications
• Functional
• Concurrent
• Distributed
• Fault-Tolerant

Erlang

Functional

• Immutability
• Pattern-Matching

-module(fact).
-export([fac/1]).

fac(0) -> 1;
fac(N) when N > 0, is_integer(N) -> N * fac(N-1).

Erlang

Concurrent

• Actor model
  • The language name them Process
  • Each process has a state
  • Each process can receive messages
  • Each process can reply to messages
  • Process has to be known to be accessible

Erlang

Distributed

• Each Erlang system running is called a node
• Connection between node is down on first call 
• Messages between nodes are transparent

Erlang

Fault-tolerant

• Supervision tree
  • Tree containing supervisors and workers
  • Workers are processes, they do the work
  • Supervisors monitor workers health
  • Supervisors decide the restart strategy when a worker die

Erlang

Fault-tolerant

S1

S2

S3

S4

S5

P1

P2

P3

P4

Erlang

Why is it still so confidential?

• Steep learning curve
  • Different way of reasoning about our apps
  • Documentation lightweight
  • Community not easily reachable as beginner
• Not a lot of communications
• Syntax hard to understand for most developers

Elixir

History​

• New language (2012)
• Created by José Valim
• Based on the ErlangVM
• Aim of adding a different language construct
• Aim of having an excellent tooling
• Aim of having accessible documentation

Elixir

Erlang Virtual Machine

• Elixir is a language running on the Erlang VM
• It can interoperate with Erlang packages easily
• It gives access, for free, access to all the Actor & Supervision tree

Elixir

Syntax

Erlang syntax was one of the tedious part for most of the developers .

Elixir brings a more conventional syntax, looking a lot like Ruby

defmodule Fact do
  def fact(0), do: 1
  def fact(n) when n > 0 and is_integer(n) do
    n * fact(n - 1)
  end
end

Elixir

Features

• Macros: most of the language is built on top of it
• Protocols: a bit like an interface 
• Doctests: doc examples are executable
• Mix: a task runner, everything use it
• Resources: Lot of documentation, starter guides and books

Elixir

Why people use it instead of Erlang?

• Power of the Erlang VM
• Syntax easier to grasp than Erlang for most devs
• Learning curve
  • Good documentation (language & packages)
  • Good starter guides (explained in a way people not familiar with functional programming can understand)
  • Books with concrete web examples
• Communication (blog posts, conferences, books)
• Community (lot of friendly people on Slack and IRC)