Processes DIY

Echo process

Write code that will spawn another process, register this process under a given name (eg :echo) and make it reply whatever it receivers back to the sender.

Hint 0 - rememeber to register the echo process first.

Hint 1 - use recursion for looping.

Hint 2 - when a message is sent the sender process is unknown to the receiver process, therefore do not forget to include sender’s PID in the message.

defmodule Echo do
  def spawn_echo_process do
    ## Add spawning code here.
    Process.sleep(1000)
  end
end

spawn(Echo, :spawn_echo_process, [])

messages = [:first, {:second, :message}, %{"third" => 1}]

for msg <- messages do
  send(:echo, msg)

  receive do
    ^msg -> :ok
    msg -> {:error, "Unexpected message #{inspect(msg)}"}
  after
    100 -> :timeout
  end
end

Counter process

Implement a process that will work as a counter. It allows for incremenitng 1, incremating and decrementing by any numer or return current value.

Hint 0 - use recursion for looping.

Hint 1 - use recursive function’s argument to store the state.

Hint 2 - use asyncronious comunication to update counter and syncronious communication to retrive current counter’s value.

Hint 3 - think about possible race condition that may occure in your system.

Warden

Implement a process that will start and watch counter process, if the counter crushes it the warden will restart it. With an inintial value.

Hint 1 - use monitor or link with setting process flag trap_exit.

The ring

One Ring to rule them all, One Ring to find them, One Ring to bring them all and in the darkness bind them.

Implement a ring of n (where n is positive integer > 2) processes, The 1st process is forwarding a message to the second one, the second one to the 3ed one etc

graph LR;
      1 --> 2;
      2 --> 3;
      3 --> ...;
      ... --> n;
      n --> 1;