Elixir - Part 1 - Speaker Deck

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Real-time Apps With Elixir Matthew Rudy Jacobs @ Codeaholics HK

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THE PROBLEM SPACE

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Line 100s of millions of online users Can’t lose a message Don’t want downtime

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Uber 100,000s online users Can’t lose a message Don’t want downtime

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GoGoVan ? online users Can’t lose a message Don’t want downtime

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THE SOLUTION?

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Erlang The Movie

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Ericsson (in 1998) 99.9999999% UPTIME 32MS / YEAR

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Ericsson (in 1998) 99.9999999% UPTIME < 1SECOND / 20 YEARS

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Whatsapp 64 billion messages per day 700 million monthly active users 1000 servers doing the work

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4 Parts

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Erlang Elixir OTP Phoenix

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Part 1 Erlang

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WHAT IS ERLANG?

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Erlang • functional • concurrent • realtime

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Erlang • pattern matching • message passing • actors • hot code reloading

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-module(roman). -export([to_roman/1]). to_roman(0) -> []; to_roman(X) when X >= 1000 -> [$M | to_roman(X - 1000)]; to_roman(X) when X >= 100 -> digit(X div 100, $C, $D, $M) ++ to_roman(X rem 100); to_roman(X) when X >= 10 -> digit(X div 10, $X, $L, $C) ++ to_roman(X rem 10); to_roman(X) when X >= 1 -> digit(X, $I, $V, $X). digit(1, X, _, _) -> [X]; digit(2, X, _, _) -> [X, X]; digit(3, X, _, _) -> [X, X, X]; digit(4, X, Y, _) -> [X, Y]; digit(5, _, Y, _) -> [Y]; digit(6, X, Y, _) -> [Y, X]; digit(7, X, Y, _) -> [Y, X, X]; digit(8, X, Y, _) -> [Y, X, X, X]; digit(9, X, _, Z) -> [X, Z]. Complex? Ugly?

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Part 2 OTP

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OTP IS A FRAMEWORK

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OTP IS A SET OF CONVENTIONS

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YOUR APPLICATION IS MADE OF “SERVERS” “AGENTS” AND “STATE MACHINES” KEPT ALIVE BY A COMPLICATED TREE OF SUPERVISORS

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Part 3 Elixir

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Jose Valim

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#4 Rails Contributor

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Creator of Devise

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Creator of Elixir

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“I felt the same way I felt when I first saw Ruby.”

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ERLANG AND RUBY HAD A BABY

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%%% erlang -module(recursve). -export([fac/1]). fac(N) when N == 0 -> 1; fac(N) when N > 0 -> N*fac(N-1). # Ruby module Recursive def fac(n) return 1 if n == 0 fail ArgumentError unless n > 0 n*fac(n-1) end end

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# Elixir defmodule Recursive do def fac(n) when n == 0, do: 1 def fac(n) when n > 0 do n*fac(n-1) end end

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# Elixir - with tail call defmodule Recursive do def fac(0), do: 1 def fac(n) when n > 0 do fac(n, 1) end defp fac(1, acc), do: acc defp fac(n, acc) do fac(n-1, acc*n) end end

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“str”<>”ings”

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:atoms

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"with #{:interpolation}"

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[:list, “type”]

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{:tuple, “type”}

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[key: “word”, list: “…”]

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%{map: “is”, like: “a hash”}

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defmodule My.Module do def exported() do 42 end defp private() do 76 end end

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[head|tail] = [:a, :b, :c]

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defmodule Math do def sum([head|tail], acc) do sum(tail, head + acc) end def sum_list([], acc) do acc end end

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bessy = %{ type: “cow”, name: “bessy” } %{name: name} = bessy name == “bessy”

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fn x -> 2*x end

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list = [1,3,3,7] Enum.sum( Enum.map(list, fn x -> x*x end) ) # 68

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[1,3,3,7] |> Enum.map(fn x -> x*x end) |> Enum.sum # 68

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> iex

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Part 4 Phoenix

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Elixir on Phoenix

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Phoenix Ecto for the database Plug for routing Channels for websockets

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mix phoenix.new phoenix_play

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MORE NEXT TIME

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Appendix A Thoughts

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Gateway Todos Users Auth SERVICES OVER HTTP Mailer Search •HTTP •Ports •Monitoring •Scaling •Logging Issues

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Gateway Todos Users Auth A SINGLE OTP SYSTEM Mailer Search •HTTP •Ports •Monitoring •Scaling •Logging Issues