Metagrokking Elixir

Webcamp Zagreb, 2017

Transcript

1. Metagrokking Elixir
   @sasajuric
   aircloak.com
   

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2. toc
   Elixir primer
   thinking in FP
   concurrency
   facing the web
   learning tips
   

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3. https://bit.ly/elixir-wczg2017
   

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4. Erlang
   software systems
   Elixir
   dev productivity
   

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6. defmodule Hello do
   def world() do
   IO.puts("Hello, World!")
   end
   end
   Hello.world()
   

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7. spawn(...) # Kernel.spawn(...)
   abs(...) # Kernel.abs(...)
   length(...) # Kernel.length(...)
   

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8. :timer.sleep(1000)
   

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9. defmodule MyModule do
   def some_fun(a, b) do
   x = a + b
   y = a - b
   x * y
   end
   end
   

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10. def simple_fun(a,b), do: a + b
    def simple_fun(a,b), do:
    a + b
    

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11. def public_fun
    defp private_fun
    

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12. integer = 42
    float = 3.14
    string = "Hello, World!"
    

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13. :an_atom
    

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14. true # :true
    false # :false
    nil # :nil
    

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15. hello_world = {"Hello", "World"}
    

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16. hello_world = {"Hello", "World"}
    pattern term
    match operator
    

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17. {hello, world} = hello_world
    # hello = "Hello", world = "World"
    

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18. {hello, _} = hello_world
    {hello, _world} = hello_world
    

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19. {"Hello", "World"} = hello_world
    

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20. File.read(some_path)
    # {:ok, contents}
    # {:error, reason}
    

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21. case some_expression do
    pattern_1 ->
    expr_1
    expr_2
    ...
    pattern_2 ->
    ...
    ...
    end
    

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22. case File.read(some_path) do
    {:ok, contents} ->
    do_something_with(contents)
    {:error, reason} ->
    report_error(reason)
    end
    

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23. def fun(pattern_1, pattern_A), do: # ...
    def fun(pattern_2, pattern_B), do: # ...
    def fun(pattern_3, pattern_C), do: # ...
    # ...
    

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24. def fact(0), do: 1
    def fact(n), do: n * fact(n - 1)
    

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25. {:ok, contents} = File.read(some_path)
    

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26. def read!(path) do
    {:ok, contents} = File.read(path)
    contents
    end
    

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27. map = %{}
    map1 = Map.put(map, some_key, some_value)
    map2 = Map.put(map1, another_key, another_value)
    

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28. map = %{}
    map = Map.put(map, some_key, some_value)
    map = Map.put(map, another_key, another_value)
    

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29. some_expr |> some_fun(arg2, arg3)
    some_fun(some_expr, arg2, arg3)
    

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30. map =
    %{}
    |> Map.put(some_key, some_value)
    |> Map.put(another_key, another_value)
    

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31. try do
    original_data
    |> trans_1(...)
    |> trans_2(...)
    ...
    |> trans_n(...)
    rescue _ ->
    original_data
    end
    

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32. item = %{
    id: 1,
    name: "beer",
    quantity: 6
    }
    

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33. item.id
    item.name
    item.quantity
    

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34. moar_beers = %{item | quantity: 12}
    

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35. Map.*
    

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36. list = [1, 2, 3]
    

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37. List.*
    Enum.*
    

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38. Enum.map(enumerable, predicate)
    Enum.any?(enumerable, predicate)
    Enum.filter(enumerable, predicate)
    Enum.drop_while(enumerable, predicate)
    ...
    

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39. add =
    fn x, y ->
    x + y
    end
    

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40. add.(2, 3)
    

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41. Enum.map(
    [-1, 2, -3],
    fn el -> abs(el) end
    )
    

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42. &(&1 + &2)
    fn x, y -> x + y end
    

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43. Enum.map([-1, 2, -3], &abs(&1))
    

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44. &SomeMod.some_fun/3
    fn x, y, z ->
    SomeMod.some_fun(x, y, z)
    end
    

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45. Enum.map([-1, 2, -3], &abs/1)
    

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46. test.txt
    4 6 4
    44 65 7 8
    34 6 17 23
    33 34 76 3
    9 10
    

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47. "test.txt"
    |> File.read!()
    |> String.split()
    |> Enum.map(&String.to_integer/1)
    |> Enum.sum()
    

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48. keyword = [{:foo, x}, {:bar, y}]
    

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49. keyword = [foo: x, bar: y]
    # [{:foo, x}, {:bar, y}]
    

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50. IO.inspect(
    some_term,
    [{:limit, 5}, {:pretty, true}]
    )
    

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51. IO.inspect(
    some_term,
    [limit: 5, pretty: true]
    )
    

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52. IO.inspect(
    some_term,
    limit: 5, pretty: true
    )
    

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53. https://github.com/sasa1977/metagrokking_elixir
    

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54. code
    

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55. list = new ShoppingList()
    list = ShoppingList.new()
    OO
    FP
    

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56. list.entries()
    ShoppingList.entries(list)
    OO
    FP
    

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57. list.add_entry(...)
    list2 = ShoppingList.add_entry(list, ...)
    OO
    FP
    

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58. val = obj.getter()
    {val, new_data} = MyMod.getter(data)
    OO
    FP
    

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59. concurrent Elixir
    

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60. # process 1
    spawn(fn ->
    # process 2
    end)
    # process 1
    

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61. scheduler scheduler scheduler scheduler
    BEAM
    CPU CPU CPU CPU
    

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62. my_pid = self()
    spawned_pid = spawn(fn -> ... end)
    

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63. send(pid, message)
    

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64. receive do
    pattern_1 ->
    # ...
    pattern_2 ->
    # ...
    # ...
    end
    

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65. producer consumer
    random number
    

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66. defmodule Producer do
    ...
    defp produce_number() do
    :timer.sleep(:rand.uniform(1000))
    number = :rand.uniform(11) - 6
    IO.puts "produced #{number}"
    number
    end
    end
    

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67. defmodule Producer do
    def start(consumer_pid), do:
    spawn(fn -> loop(consumer_pid) end)
    ...
    end
    

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68. defmodule Producer do
    ...
    defp loop(consumer_pid) do
    ...
    loop(consumer_pid)
    end
    end
    

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69. defmodule Producer do
    ...
    defp loop(consumer_pid) do
    number = produce_number()
    send(consumer_pid, {:number, number})
    loop(consumer_pid)
    end
    end
    

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70. defmodule Consumer do
    ...
    defp consume(sum, number) do
    :timer.sleep(:rand.uniform(1000))
    new_sum = sum + number
    IO.puts "sum = #{new_sum}"
    new_sum
    end
    end
    

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71. defmodule Consumer do
    def start(), do:
    spawn(fn -> loop(0) end)
    ...
    end
    

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72. defmodule Consumer do
    ...
    defp loop(sum) do
    new_sum =
    receive do
    {:number, number} ->
    consume(sum, number)
    end
    loop(new_sum)
    end
    end
    

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73. consumer_pid = Consumer.start()
    Producer.start(consumer_pid)
    

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74. produced 3
    sum = 3
    produced -2
    produced -3
    sum = 1
    produced 4
    sum = -2
    sum = 2
    

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75. server process
    long-running
    passive
    stateful
    

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76. OTP framework
    

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77. GenServer.start_link(Consumer, nil)
    

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78. defmodule Consumer do
    use GenServer
    ...
    end
    

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79. defmodule Consumer do
    def init(_arg), do:
    {:ok, 0}
    ...
    end
    

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80. GenServer.cast(
    consumer_pid,
    {:number, number}
    )
    

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81. defmodule Consumer do
    ...
    def handle_cast({:number, number}, sum) do
    new_sum = consume(sum, number)
    {:noreply, new_sum}
    end
    end
    

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82. defmodule Consumer do
    def start_link(), do:
    GenServer.start_link(Consumer, nil)
    def notify(consumer_pid, number), do:
    GenServer.cast(
    consumer_pid,
    {:number, number}
    )
    ...
    end
    

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83. # producer
    Consumer.notify(consumer_pid, number)
    

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84. shopping list 1
    shopping list 2
    shopping list 3
    shopping list 4
    shopping list 5
    

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85. websocket
    shopping list server
    notification
    

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86. websocket
    request handler
    shopping list server
    modification request
    notification
    

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87. shopping list server
    

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89. code
    

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90. supervisor
    child 1 child 2 child 3
    

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91. supervisor
    worker supervisor worker
    worker worker
    1.
    2. 3.
    4. 5.
    6.
    

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92. Supervisor.start_link(
    [
    ChildModule1,
    ChildModule2,
    ChildModule3
    ],
    strategy: :one_for_one
    )
    

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93. static
    :one_for_one
    :one_for_all
    :rest_for_one
    dynamic :simple_one_for_one
    

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94. Supervisor.start_link(
    [ChildModule],
    strategy: :simple_one_for_one
    )
    

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95. Supervisor.start_child(
    supervisor_pid,
    [arg1, arg2, ...]
    )
    

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96. service supervisor
    list service 1 list service n
    …
    

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97. Supervisor.start_link(
    [ShoppingList.Service],
    name: :service_supervisor,
    strategy: :simple_one_for_one
    )
    

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98. Supervisor.start_child(
    :service_supervisor,
    ...
    )
    

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99. code
    

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100. request handler
     request for shopping list 123
     

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101. client
     list service
     process registry
     who is in charge of
     {:shopping_list_service, 123} ?
     register me as
     {:shopping_list_service, 123}
     

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102. backend system
     list service registry service supervisor
     

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103. code
     

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104. shopping list service
     ShoppingList
     add/update/delete
     

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105. entry added list_id 1 entry_id: 1 name: eggs quantity: 12
     entry updated list_id 2 entry_id: 1 quantity: 6
     entry deleted list_id 3 entry_id: 1
     ...
     

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106. code
     

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107. shopping list service
     websocket process
     websocket process
     websocket process
     websocket process
     

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108. subscriber
     shopping list service
     subscribe
     entries
     

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109. shopping list service
     ShoppingList
     add/update/delete
     subscriber
     

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110. code
     

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111. shopping list service
     ShoppingList
     add/update/delete
     subscriber
     

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112. subscribe
     subscription
     add/update/delete
     command
     apply event
     

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113. list service
     subscription command
     

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114. subscription command
     prepare event
     commit
     

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115. GenServer server process (service)
     Supervisor starting/stopping/restarting
     registered name static service discovery
     Registry dynamic service discovery
     Application auto start
     

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116. Task
     GenServer
     Supervisor
     registered name
     Application
     Registry
     

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117. functional Elixir
     organizing code
     concurrent Elixir
     organizing runtime
     

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118. web-facing system
     

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119. code
     

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120. It’s small, it’s elegant, it’s thoughtful, it’s fun,
     and it’s very, very, very readable once you flip
     over into functional programming mentality,
     which took my intern a week.
     Steve Cohen, Pinterest
     One week. That is how long it took for our
     engineers, who had all (but one) worked
     with Rails for a few years, to be productive on
     a new Phoenix client project.
     Brian Cardarella, Dockyard
     

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121. strategy
     learn the basics
     produce
     improve
     

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122. bootstrap
     Elixir guides
     Phoenix guides
     

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123. produce
     toy project
     prototype
     gradual migration
     

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124. consult
     Elixir reference
     Phoenix reference
     Ecto reference
     Erlang reference
     Erlang vs Elixir syntax
     

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125. community
     Elixir forum
     IRC
     Slack
     

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126. learning resources
     Elixir
     Phoenix
     

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127. https://bit.ly/elixir-wczg2017
     40% off Elixir in Action with code ctwwebczg17 at
     https://www.manning.com/books/elixir-in-action
     

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