Metagrokking Elixir - Speaker Deck

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Metagrokking Elixir @sasajuric aircloak.com

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

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https://bit.ly/elixir-wczg2017

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Erlang software systems Elixir dev productivity

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No content

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

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

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:timer.sleep(1000)

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

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

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def public_fun defp private_fun

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

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:an_atom

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true # :true false # :false nil # :nil

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hello_world = {"Hello", "World"}

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

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

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

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{"Hello", "World"} = hello_world

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

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

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

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

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

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

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

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

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

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

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

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

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item.id item.name item.quantity

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moar_beers = %{item | quantity: 12}

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Map.*

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list = [1, 2, 3]

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List.* Enum.*

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

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

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add.(2, 3)

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

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

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

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

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

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

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

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

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

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

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

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

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https://github.com/sasa1977/metagrokking_elixir

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code

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

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

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

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

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concurrent Elixir

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

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scheduler scheduler scheduler scheduler BEAM CPU CPU CPU CPU

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

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send(pid, message)

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

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producer consumer random number

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

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

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

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

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

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server process long-running passive stateful

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OTP framework

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GenServer.start_link(Consumer, nil)

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defmodule Consumer do use GenServer ... end

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

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

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

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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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# producer Consumer.notify(consumer_pid, number)

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shopping list 1 shopping list 2 shopping list 3 shopping list 4 shopping list 5

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websocket shopping list server notiﬁcation

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websocket request handler shopping list server modiﬁcation request notiﬁcation

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shopping list server

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code

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supervisor child 1 child 2 child 3

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

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

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static :one_for_one :one_for_all :rest_for_one dynamic :simple_one_for_one

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

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

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service supervisor list service 1 list service n …

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

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Supervisor.start_child( :service_supervisor, ... )

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code

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request handler request for shopping list 123

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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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backend system list service registry service supervisor

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code

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shopping list service ShoppingList add/update/delete

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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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code

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shopping list service websocket process websocket process websocket process websocket process

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subscriber shopping list service subscribe entries

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shopping list service ShoppingList add/update/delete subscriber

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code

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shopping list service ShoppingList add/update/delete subscriber

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subscribe subscription add/update/delete command apply event

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list service subscription command

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subscription command prepare event commit

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

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Task GenServer Supervisor registered name Application Registry

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functional Elixir organizing code concurrent Elixir organizing runtime

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web-facing system

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code

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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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strategy learn the basics produce improve

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bootstrap Elixir guides Phoenix guides

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produce toy project prototype gradual migration

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

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community Elixir forum IRC Slack

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learning resources Elixir Phoenix

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