Introducing Elixir: Self-healing applications at ZOMG scale

Elixir is a new functional language built on the Erlang VM. We’ll tour the Elixir language and it’s most important frameworks to discover what makes Elixir a great choice for building systems at ZOMG scale and how those systems stay up for so long with Wolverine level self-healing.

Elixir’s secret is in its Erlang heritage. When was the last time your telephone network went down? Never, right? That’s because most of the telephone network is written in Erlang. How does WhatsApp manage to support 1.2 billion users and deliver 42 billion messages a day with only around 50 engineers? Yes, Erlang.

Elixir takes the power and stability offered by Erlang and makes it more approachable, with a Ruby inspired syntax, simpler abstractions and some powerful tools which will enable you to build concurrent, fault-tolerant and distributed systems. We'll find out how this functional language is the most Object Oriented of all languages and how microservice architecture is built right in.

Challenge yourself to break out of your comfort zone and look at how other languages solve problems. You’ll become a better developer if you do.

Transcript

1. Introducing Elixir Self-healing applications at ZOMG scale @andypike
2. Allow myself to introduce… …myself
3. @andypike
4. Freelancer for hire!
8. Background
10. Hello Mike Hello Robert Hello Joe Erlang The Movie https://youtu.be/xrIjfIjssLE
11. 2 million connections per server 1.2 billion users 42 billion messages per day
12. Operating System BEAM VM Erlang Bytecode Elixir LFE
14. Elixir Basics
15. Functional Immutable Concurrent Fault Tolerant Ruby Inspired Syntax Distributed
16. $ iex iex(1)> $ iex hello.exs iex(1)> Hello.world() "Hello World" iex(2)> h String.upcase Converts all characters in the given string to uppercase. ## Examples iex> String.upcase("abcd") "ABCD"
17. Basic Types
18. $ iex iex(1)> 1 + 1 2 iex(2)> 2 * 3 6 iex(3)> 1.2 - 0.2 1.0 iex(4)> 1..10 1..10 iex(5)> "Hello World" "Hello World" iex(6)> :andy :andy
19. iex(1)> { :ok, 42, "next" } { :ok, 42, "next" } iex(2)> [1, 2, 3] [1, 2, 3] iex(3)> [1, 2, 3] ++ [4, 5, 6] [1, 2, 3, 4, 5, 6] iex(4)> info = %{ :name => "Andy", :town => "Woking" } %{name: "Andy", town: "Woking"} iex(5)> info[:name] "Andy" iex(6)> info.name "Andy"
20. person.exs defmodule Person do
 defstruct name: "", age: 0, email: "" end $ iex person.exs iex(1)> p1 = %Person{ name: "Andy", age: 25 } %Person{age: 25, email: "", name: "Andy"} iex(2)> p1.name "Andy" iex(3)> p2 = %Person{ p1 | email: "me@here.com" } %Person{age: 25, email: "me@here.com", name: "Andy"} iex(4)> p1.email ""
21. Pattern Matching
22. iex(1)> a = 1 1 iex(2)> a + 2 3 iex(3)> a = 2 2 iex(4)> 2 = a 2 iex(5)> 3 = a ** (MatchError) no match of right hand side value: 2 iex(6)> ^a = 3 ** (MatchError) no match of right hand side value: 3
23. iex(1)> list = [1, 2, 3] [1, 2, 3] iex(2)> [x, y, z] = list [1, 2, 3] iex(3)> y 2 iex(4)> [1, b, c] = list [1, 2, 3] iex(5)> b 2 iex(6)> [3, t, 5] = list ** (MatchError) no match of right hand side value: [1, 2, 3]
24. iex(1)> success = { :ok, 42 } { :ok, 42 } iex(2)> failure = { :error, "Oops" } { :error, "Oops" } iex(3)> { :ok, result } = success { :ok, 42 } iex(4)> result 42 iex(5)> { :ok, result } = failure ** (MatchError) no match of right hand side value: {:error, "Oops"} iex(6)> { _, result } = failure { :error, "Oops" }
25. iex(1)> list = [1, 2, 3] [1, 2, 3] iex(2)> [head|tail] = list [1, 2, 3] iex(3)> head 1 iex(4)> tail [2, 3] iex(5)> [head_2|tail_2] = tail [2, 3] iex(6)> head_2 2 iex(7)> tail_2 [3]
26. Functions
27. defmodule Hello do def world do "Hello World" end def world(name) do "Hello #{name}" end end iex(1)> Hello.world "Hello World" iex(2)> Hello.world("Andy") "Hello Andy"
28. defmodule Hello do def world, do: greeting("World") def world(name), do: greeting("Hi", name) defp greeting(salutation \\ "Hello", name) do "#{salutation} #{name}" end end iex(1)> Hello.world "Hello World" iex(2)> Hello.world("Andy") "Hi Andy" iex(3)> Hello.greeting("Andy") ** (UndefinedFunctionError) function Hello.greeting/1 is undefined or private
29. defmodule Maths do def arithmetic(:add, a, b), do: a + b def arithmetic(:subtract, a, b), do: a - b end iex(1)> Maths.arithmetic(:add, 1, 2) 3 iex(2)> Maths.arithmetic(:subtract, 10, 2) 8 iex(2)> Maths.arithmetic(:multiply, 3, 3) ** (FunctionClauseError) no function clause matching…
30. defmodule MyList do def count([]), do: 0 def count([_ | tail]) do 1 + count(tail) end end iex(1)> MyList.count([]) 0 iex(2)> MyList.count([1, 2, 3]) 3
31. defmodule MyList do def count(list, total \\ 0) def count([], total), do: total def count([_ | tail], total) do count(tail, total + 1) end end iex(1)> MyList.count([]) 0 iex(2)> MyList.count([1, 2, 3]) 3
32. defmodule Guard do def what_is(x) when is_atom(x) do IO.puts "#{x} is an atom" end def what_is(x) when is_number(x) and x > 0 do IO.puts "#{x} is a positive number" end def what_is(_), do: IO.puts "Unknown" end iex(1)> Guard.what_is(10) 10 is a positive number iex(2)> Guard.what_is("Andy") Unknown
33. iex(1)> String.downcase("ANDY") "andy" iex(2)> String.ends_with?("Andy", "y") true iex(3)> Enum.map([1, 2, 3], fn(x) -> x * x end) [1, 4, 9] iex(4)> Enum.map([1, 2, 3], &(&1 * &1)) [1, 4, 9] iex(5)> Map.has_key?(%{ name: "Andy" }, :name) true
34. Pipe Operator
35. text = " Hi Andy " text = String.downcase(text) text = String.strip(text) text = String.reverse(text) => "ydna ih" String.reverse(String.strip(String.downcase(text))) => "ydna ih"
36. text = " Hi Andy " text |> String.downcase |> String.strip |> String.reverse => "ydna ih"
37. Doctests
38. defmodule MyString do @doc ~S""" Converts a string to uppercase ## Examples iex> MyString.upcase("andy") "ANDY" """ def upcase(string) do String.upcase(string) end end
39. defmodule MyStringTest do use ExUnit.Case doctest MyString end $ mix test 1 test, 0 failures iex(1)> h MyString.upcase Converts a string to uppercase ## Examples iex> MyString.upcase("andy") "ANDY"
40. Concurrent
41. Processes
42. iex(1)> pid = spawn(fn -> IO.puts "Hello World" end) Hello World #PID<0.82.0> iex(2)> Process.alive?(pid) false
43. defmodule Chat do def greet do IO.puts "Hello World" end end iex(1)> pid = spawn(Chat, :greet, []) Hello World #PID<0.82.0>
44. Sending Messages
45. Memory Function fn -> IO.puts "Hello World" end Mailbox Message 1 Message 2 Message 3
46. defmodule ChatWorker do def loop do receive do { :greet, name } -> IO.puts "Hi #{name}!" loop() end end end iex(1)> pid = spawn(ChatWorker, :loop, []) #PID<0.118.0> iex(2)> Process.alive?(pid) true
47. defmodule ChatWorker do def loop do receive do { :greet, name } -> IO.puts "Hi #{name}!" loop() end end end iex(3)> send pid, { :greet, "Andy" } Hi Andy! iex(4)> Process.alive?(pid) true
48. defmodule NothingWorker do def loop do receive do { :exit } -> IO.puts "Exiting…" _ -> loop() end end end iex(1)> pid = spawn(NothingWorker, :loop, []) iex(2)> send pid, { :covfefe } iex(3)> Process.alive?(pid) true
49. defmodule NothingWorker do def loop do receive do { :exit } -> IO.puts "Exiting…" _ -> loop() end end end iex(4)> send pid, { :exit } Exiting… iex(3)> Process.alive?(pid) false
50. State
51. defmodule Counter do def init(count \\ 0) do loop(count) end def loop(count) do receive do { :add, number } -> count = count + number loop(count) { :current, sender } -> send(sender, { :ok, count }) loop(count) end end end
52. iex(1)> pid = spawn(Counter, :init, []) #PID<0.88.0> iex(2)> send(pid, {:add, 1}) {:add, 1} iex(3)> send(pid, {:add, 2}) {:add, 2} iex(4)> send(pid, {:current, self()}) {:current, #PID<0.80.0>} iex(5)> flush() {:ok, 3} :ok
53. IEX <0.80.0> Counter.loop <0.88.0> {:add, 1} {:add, 2} {:current, <0.80.0>} {:ok, 3}
54. spawn init loop exit Message Message Message State
55. OTP
56. use GenServer GenServer.start_link MyModule.init GenServer.call MyModule.handle_call GenServer.cast MyModule.handle_cast
57. defmodule OTPCounter do use GenServer # Public API def start_link do GenServer.start_link(__MODULE__, :ok, []) end # Callbacks def init(:ok) do {:ok, 0} end end initial state
58. defmodule OTPCounter do # snip… # Public API def current(pid) do GenServer.call(pid, :current) end # Callbacks def handle_call(:current, from_pid, state) do {:reply, state, state} end end
59. defmodule OTPCounter do # snip… # Client API def add(pid, number) do GenServer.cast(pid, {:add, number}) end # Callbacks def handle_cast({:add, number}, state) do {:noreply, state + number} end end
60. # Public API def stop(pid) do GenServer.cast(pid, :stop) end # Callbacks def handle_cast(:stop, state) do {:stop, :normal, state} end def terminate(reason, state) do IO.puts "Server stopping with total #{state}" :ok end
61. iex(1)> {:ok, pid} = OTPCounter.start_link {:ok, #PID<0.94.0>} iex(2)> OTPCounter.current(pid) 0 iex(3)> OTPCounter.add(pid, 1) :ok iex(4)> OTPCounter.add(pid, 1) :ok iex(5)> OTPCounter.current(pid) 2 iex(6)> OTPCounter.stop(pid) Server stopping with total 2 iex(7)> Process.alive?(pid) false
63. The Scheduler
64. Process 1 Process 2 Process 3 Process 4 Run Queue Current Process Until empty mailbox or 2000 reductions
65. Core 1 Core 2 Core 3 Core 4
66. Fault-Tolerant
67. What’s the one universal way to fix any computer problem?
68. "Have you tried turning it off and back on again?"
69. Supervision Trees
70. Worker Worker Supervisor Supervisor Worker Worker
71. defmodule OTPCounter do # snip… def crash(pid) do GenServer.cast(pid, :crash) end def handle_cast(:crash, state) do 1/0 end end
72. iex> self() #PID<0.80.0> iex> import Supervisor.Spec Supervisor.Spec iex> c = [worker(OTPCounter, [], [])] … iex> {_, sup} = Supervisor.start_link(c, strategy: :one_for_one) {:ok, #PID<0.90.0>} iex> {_, [_, counter]} = Process.info(sup, :links) {:links, [#PID<0.80.0>, #PID<0.91.0>]}
73. iex> OTPCounter.add(counter, 1) :ok iex> OTPCounter.current(counter) 1 iex> OTPCounter.crash(counter) [error] GenServer #PID<0.91.0> terminating… iex> {_, [_, counter]} = Process.info(sup, :links) {:links, [#PID<0.80.0>, #PID<0.95.0>]} iex> OTPCounter.current(counter) 0
74. Let it crash
75. Distributed
76. Node :foo Core 1 Core n . . . Core 1 Core n . . . Node :bar msg
77. $ iex --name foo@192.168.0.100 --cookie s3cr3t iex(foo@192.168.0.100)1> Node.connect(:"bar@192.168.0.101") true iex(foo@192.168.0.100)2> Node.list [:"bar@192.168.0.101"] iex(foo@192.168.0.100)3> c "chat_worker.exs" [ChatWorker] $ iex --name bar@192.168.0.101 --cookie s3cr3t iex(bar@192.168.0.101)1> Node.list [:"foo@192.168.0.100"] iex(bar@192.168.0.101)2> ChatWorker.loop ** (UndefinedFunctionError) function ChatWorker.loop/0 is undefined
78. $ iex --name foo@192.168.0.100 --cookie s3cr3t iex(foo@192.168.0.100)1> Node.connect(:"bar@192.168.0.101") true iex(foo@192.168.0.100)2> Node.list [:"bar@192.168.0.101"] iex(foo@192.168.0.100)3> c "chat_worker.exs" [ChatWorker] iex(bar@192.168.0.101)3> pid = Node.spawn_link :"foo@192.168.0.100", ChatWorker, :loop, [] #PID<9137.108.0> iex(bar@192.168.0.101)4> send(pid, {:greet, "Andy"}) Hi Andy!
80. Frameworks, Libraries & Tools
82. Framework Throughput (req/s) Avg Latency (ms) Phoenix 31,417 3.52 Express 9,477 10.56 Sinatra 8,334 7.46 Rails 3,452 17.96 https://github.com/mroth/phoenix-showdown/blob/master/RESULTS_v3.md
83. http://www.phoenixframework.org/blog/the-road-to-2-million-websocket-connections
85. hex mnesia ETS Hot code upgrades mix observer
86. Resources
87. elixir-lang.org exercism.io elixirschool.com learnelixir.tv learnphoenix.tv elixirfountain.com codeschool.com redfour.io
89. Final Thoughts
90. iMac Pro 18-cores Intel X-Series 18-cores Apple Watch Series 2 Dual-core Raspberry PI Quad-core
91. "I thought of objects being like biological cells or individual computers on a network, only able to communicate with messages." - Alan Kay
94. Thank you! @andypike
95. Sponsors