Processes. OTP. Elixir

Transcript

1. Никита Соболев
   github.com/sobolevn
   

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3. Процессы. ОТP.
   Elixir
   

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4. План доклада
   • Концепция
   • OTP
   • Elixir specific штуки
   

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5. Для кого мой доклад?
   • Вы слышали про Erlang/Elixir
   • Вы читали туториал
   • Вы знакомы с другими функциональными
   языками
   

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6. Actor Model
   

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7. OTP
   

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8. Supervisor
   

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9. defmodule FpconfElixir do
   use Application
   def start(_type, _args) do
   import Supervisor.Spec, warn: false
   children =
   [
   worker(FpconfElixir.AgentType, []),
   worker(FpconfElixir.GenStageType.Producer, [0]),
   worker(FpconfElixir.GenStageType.ProducerConsumer, []),
   worker(FpconfElixir.GenStageType.Consumer, [])
   ]
   opts = [strategy: :one_for_one,
   name: FpconfElixir.Supervisor]
   Supervisor.start_link(children, opts)
   end
   end
   

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13. :permanent
    :temporary
    :transient
    

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14. spawn
    

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15. spawn fn -> IO.puts("I am a process!") end
    

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16. defmodule FpconfElixir.SpawnType do
    def start_link do
    accepting_messages(0)
    end
    def accepting_messages(state) do
    receive do
    {:hello, message} ->
    IO.puts "Hello, #{message}"
    # Will accept only once without this:
    accepting_messages(state)
    {:counter} ->
    new_state = state + 1
    IO.puts "New state is #{new_state}"
    accepting_messages(new_state)
    _ ->
    IO.puts "What?"
    accepting_messages(state)
    end
    end
    end
    

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17. pid = spawn fn ->
    FpconfElixir.SpawnType.start_link
    end
    send pid, {:hello, "world"}
    # => Hello, world
    send pid, {:counter}
    # => New state is 1
    send pid, {:counter}
    # => New state is 2
    send pid, {:other}
    # => What?
    

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18. spawn_link
    

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19. spawn_link fn -> raise "Oops" end
    spawn fn -> raise "Oops" end
    

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20. GenServer
    

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21. defmodule FpconfElixir.TodoList do
    use GenServer
    def start_link do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
    end
    def add_task(task) when is_binary(task) do
    GenServer.cast(__MODULE__, {:add, task})
    end
    def list_tasks, do: GenServer.call(__MODULE__, :list)
    # Private
    def handle_cast({:add, task}, tasks), do:
    {:noreply, [task | tasks]}
    def handle_call(:list, _from, tasks), do:
    {:reply, tasks, tasks}
    end
    

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22. FpconfElixir.TodoList.add_task("One")
    # => :ok
    FpconfElixir.TodoList.add_task("Two")
    # => :ok
    FpconfElixir.TodoList.list_tasks
    # => ["One", "Two"]
    

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25. Agent
    

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26. defmodule FpconfElixir.AgentType do
    use Agent
    @doc """
    Starts a new Agent process with an empty Map.
    """
    def start_link do
    Agent.start_link(fn -> %{} end,
    name: __MODULE__) # this process is a singleton
    end
    def get(key) do
    Agent.get(__MODULE__, &Map.get(&1, key))
    end
    def put(key, value) do
    Agent.update(__MODULE__, fn (state) ->
    Map.put(state, key, value) # happens on server
    end)
    end
    end
    

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28. alias FpconfElixir.AgentType
    AgentType.put("name", "Nikita")
    # =>:ok
    AgentType.get("Name")
    # => "Nikita"
    

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30. ets
    

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31. table = :ets.new(:personal_table, [
    :set, :protected, :named_table
    ])
    :ets.insert(table, {"surname", "Sobolev"})
    :ets.lookup(table, "surname")
    

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34. ets => 0.40 µs
    agent => 6 µs
    redis => 210 µs
    

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35. Task
    

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36. task = Task.async(fn -> do_some_work() end)
    res = do_some_other_work()
    res + Task.await(task)
    

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37. Task.Supervisor.async({
    FpconfElixir.TaskSupervisor, :remote@local
    },
    HttpParser, :parse, ["head", "body"]
    )
    

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38. GenStage
    

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39. [A] -> [B] -> [C]
    

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40. defmodule FpconfElixir.GenStageType.Producer do
    use GenStage
    def start_link(initial \\ 0) do
    GenStage.start_link(__MODULE__, initial,
    name: __MODULE__)
    end
    def init(counter), do: {:producer, counter}
    def handle_demand(demand, state) do
    events = Enum.to_list(state..(state + demand - 1))
    {:noreply, events, state + demand}
    end
    end
    

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41. defmodule FpconfElixir.GenStageType.ProducerConsumer do
    use GenStage
    def start_link do
    GenStage.start_link(__MODULE__, :state_doesnt_matter,
    name: __MODULE__)
    end
    def init(state) do
    {:producer_consumer, state, subscribe_to: [
    FpconfElixir.GenStageType.Producer]}
    end
    def handle_events(events, _from, state) do
    numbers =
    events
    |> Enum.filter(&(rem(&1, 2) == 0))
    {:noreply, numbers, state}
    end
    end
    

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42. defmodule FpconfElixir.GenStageType.Consumer do
    use GenStage
    def start_link do
    GenStage.start_link(__MODULE__, :state_doesnt_matter)
    end
    def init(state) do
    {:consumer, state, subscribe_to: [
    FpconfElixir.GenStageType.ProducerConsumer]}
    end
    def handle_events(events, _from, state) do
    for event <- events do
    IO.inspect({self(), event, state})
    end
    # As a consumer we never emit events
    {:noreply, [], state}
    end
    end
    

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45. Real world example
    A. Берем список репозиториев пользователя с
    Github
    B. Для каждого репозитория получим всех, кто
    ставил звездочку
    C. Сохраним их себе в базу для опытов
    

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46. Flow
    

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47. File.stream!("source.txt", [], :line)
    |> Flow.from_enumerable()
    |> Flow.flat_map(&String.split/1)
    |> Flow.partition() # the magic happens here
    |> Flow.reduce(fn -> %{} end, fn(word, map) ->
    Map.update(map, word, 1, &(&1 + 1))
    end)
    |> Enum.into(%{})
    

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48. Стоит упомянуть
    • OTP application
    • gen_fsm, GenEvent
    • gen_metrics
    • mnesia
    

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49. Полезные материалы
    • https://github.com/sasa1977/exactor
    • https://github.com/onetapbeyond/
    gen_metrics
    • https://github.com/saleyn/erlexec
    • https://github.com/PragTob/benchee
    

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50. http://elixir-lang.moscow
    

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51. http://wunsh.ru
    

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52. Вопросы?
    github.com/sobolevn
    

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