Concurrency in Elixir with OTP
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The document discusses concurrency in Elixir using OTP (Open Telecom Platform). OTP provides libraries and design principles for writing concurrent applications in Erlang/Elixir. It includes components like supervisors, applications, agents, tasks and GenServers that help manage concurrency. Supervisors oversee worker processes in a supervision tree, restarting them based on configured restart strategies if they fail. State is managed by agents and GenServers. This allows applications to have many concurrent processes that are fault tolerant and can seamlessly spread across machines.
![Starts Supervisors
Application
# mix.exs
def application do
[mod: { CatFeed, [] }]
end
# lib/cat_feed.ex
defmodule CatFeed do
use Application
def start(_type, _args) do
CatFeed.Supervisor.start_link
end
end](https://image.slidesharecdn.com/elixirotp1-140823185439-phpapp02/85/Concurrency-in-Elixir-with-OTP-12-320.jpg)
![Supervises processes
Supervisor
# lib/cat_feed/supervisor.ex
defmodule CatFeed.Supervisor do
use Supervisor
def start_link do
Supervisor.start_link(__MODULE__, :ok)
end
def init(:ok) do
children = [ worker(CatFeed.FeederLady) ]
supervise children, strategy :one_for_one
end
end](https://image.slidesharecdn.com/elixirotp1-140823185439-phpapp02/85/Concurrency-in-Elixir-with-OTP-13-320.jpg)
![Supervises processes
Supervisor
# lib/cat_feed/supervisor.ex
defmodule CatFeed.Supervisor do
use Supervisor
def start_link do
Supervisor.start_link(__MODULE__, :ok)
end
def init(:ok) do
children = [ worker(CatFeed.FeederLady) ]
supervise children, strategy :one_for_one
end
end](https://image.slidesharecdn.com/elixirotp1-140823185439-phpapp02/85/Concurrency-in-Elixir-with-OTP-14-320.jpg)
![# lib/cat_feed/supervisor.ex
defmodule CatFeed.Supervisor do
use Supervisor
def start_link do
Supervisor.start_link(__MODULE__, :ok)
end
def init(:ok) do
children = [ worker(CatFeed.FeederLady) ]
supervise children, strategy :one_for_one
end
end
Concurrency](https://image.slidesharecdn.com/elixirotp1-140823185439-phpapp02/85/Concurrency-in-Elixir-with-OTP-28-320.jpg)
![# lib/cat_feed/supervisor.ex
defmodule CatFeed.Supervisor do
use Supervisor
# def start_link do // folded
def init(:ok) do
children = [
worker(CatFeed.FeederLady),
worker(CatFeed.FeederLady),
CatFeed.Supervisor.start_link
]
supervise children, strategy :one_for_one
end
end
Concurrency](https://image.slidesharecdn.com/elixirotp1-140823185439-phpapp02/85/Concurrency-in-Elixir-with-OTP-29-320.jpg)
Concurrency in Elixir with OTP
- 1. Concurrency in Elixir with OTP Presented for Code & Supply
- 3. You down with OTP? Yeah you know me!
- 4. Open Telecom Platform W hat is OTP?
- 5. Open Telecom Platform W hat is OTP? Open source project Developed by Ericsson, opened in 1998 18 years proven https://github.com/erlang/otp
- 6. Open Telecom Platform W hat is OTP? Fault tolerant Distributed Concurrent
- 7. Open Telecom Platform W hat is OTP? Design principles for writing concurrent applications in Erlang Libraries
- 9. History xgen Integrates Elixir, Mix and OTP Merged into Elixir Available in Elixir 0.13.3 and higher https://github.com/josevalim/xgen
- 11. Concurrency
- 12. Starts Supervisors Application # mix.exs def application do [mod: { CatFeed, [] }] end # lib/cat_feed.ex defmodule CatFeed do use Application def start(_type, _args) do CatFeed.Supervisor.start_link end end
- 13. Supervises processes Supervisor # lib/cat_feed/supervisor.ex defmodule CatFeed.Supervisor do use Supervisor def start_link do Supervisor.start_link(__MODULE__, :ok) end def init(:ok) do children = [ worker(CatFeed.FeederLady) ] supervise children, strategy :one_for_one end end
- 14. Supervises processes Supervisor # lib/cat_feed/supervisor.ex defmodule CatFeed.Supervisor do use Supervisor def start_link do Supervisor.start_link(__MODULE__, :ok) end def init(:ok) do children = [ worker(CatFeed.FeederLady) ] supervise children, strategy :one_for_one end end
- 15. one_for_one If a child process terminates, only that process is restarted. Restart Strategies
- 16. one_for_one If a child process terminates, only that process is restarted. Restart Strategies
- 17. one_for_one If a child process terminates, only that process is restarted. Restart Strategies
- 18. rest_for_one Restarts all processes started after one that failed Restart Strategies
- 19. rest_for_one Restarts all processes started after one that failed Restart Strategies
- 20. rest_for_one Restarts all processes started after one that failed Restart Strategies
- 21. one_for_all Restarts all processes if any fail Restart Strategies
- 22. one_for_all Restarts all processes if any fail Restart Strategies
- 23. one_for_all Restarts all processes if any fail Restart Strategies
- 24. Handles state and does things GenServer # lib/cat_feed/feeder_lady.ex defmodule CatFeed.FeederLady do use Server # some stuff here … def handle_call({:fill, bowl}, _from, state) do {:reply, CatFeed.BowlAgent.put(bowl, :food, state), state} # or HashDict.put(bowl, key, value) end end
- 25. Specialized for storing state Agent # lib/cat_feed/bowl_agent.ex defmodule CatFeed.BowlAgent do def start_link do # set initial state Agent.start_link(fn -> HashDict.new end) end def get(bucket, key) do # get state Agent.get(bucket, &HashDict.get(&1, key)) end def put(bowl, key, value) do # update state Agent.update(bowl, &HashDict.put(&1, key, value)) end end
- 27. Handled in supervisor BEAM processes Spread across machines seamlessly Concurrency
- 28. # lib/cat_feed/supervisor.ex defmodule CatFeed.Supervisor do use Supervisor def start_link do Supervisor.start_link(__MODULE__, :ok) end def init(:ok) do children = [ worker(CatFeed.FeederLady) ] supervise children, strategy :one_for_one end end Concurrency
- 29. # lib/cat_feed/supervisor.ex defmodule CatFeed.Supervisor do use Supervisor # def start_link do // folded def init(:ok) do children = [ worker(CatFeed.FeederLady), worker(CatFeed.FeederLady), CatFeed.Supervisor.start_link ] supervise children, strategy :one_for_one end end Concurrency
- 30. Recap OTP Based on Erlang OTP Supervision tree Restart strategies State managed by select entities
- 31. Concurrency in Elixir with OTP Presented for Code & Supply http://codeandsupply.co @justinxreese