Learn Elixir with us.

[mattgreg]

If you have general questions about Elixir or how/why we use it at Ockam - join the thread below...

[sleipnir]

Hi! Great library and protocol efforts.

There are some examples of use Ockam with Elixir?
We trying to use Ockam integrated with libcluster library for connecting, list, and disconnecting nodes.

[sleipnir]

These were the steps I followed:

1. Create a worker

defmodule OckamPoc.Worker do
  use Ockam.Worker
  require Logger

  @impl true
  def handle_message(message, state) do
    Logger.info("Received message #{inspect(message)}")
    {:ok, state}
  end
end

2. Create listener and message then route:

Ockam.Transport.TCP.Listener.create(ip: {127,0,0,1}, port: 4000)

Ockam.Transport.TCP.Client.create(destination: %{ip: {127,0,0,1}, port: 4000})

address = %Ockam.Transport.TCPAddress{ip: {127,0,0,1}, port: 4000}

OckamPoc.Worker.create(address: "worker")

message = %{onward_route: [address, "worker"], payload: "hello"}

Ockam.Router.route(message)

The only console output is :ok but the message is never delivered to my worker

I would really like to use Ockam but it lacks some documentation and without help I don't see how I could use this library.

[mrinalwadhwa]

@sleipnir thanks for sharing the steps. The TCP client seems to have a routing related bug. We don't use the Elixir TCP client much so far... so it hasn't gotten a lot of attention. I've filed the bug here. Thank you for helping us find it.

We're really excited you want to use Ockam in your project but I want to say this again so you're aware of what you're taking on. The Elixir lib is experimental, which is why we haven't published it to hex.pm yet. We want to have less bugs 😀, proper docs and a stable API when we take the elixir library to developer preview. We're a small team and our current focus is on getting the right docs/examples in place for the Rust lib first.

[sleipnir]

Thanks @mrinalwadhwa

[sleipnir]

I'll see if I can help with this issue

[hairyhum]

Hi @sleipnir
There are some API issues in the TCP transport. One of them is carried over from the UDP transport, which is that TCP listener acts as a proxy to create clients and route outgoing traffic. This allows routing outgoing TCP messages using the TCPAddress.
But in order to do so, the listener needs to be configured with route_outgoing: true option.

Ockam.Transport.TCP.Listener.create(ip: {127,0,0,1}, port: 4000, route_outgoing: true)

address = %Ockam.Transport.TCPAddress{ip: {127,0,0,1}, port: 4000}

OckamPoc.Worker.create(address: "worker")

message = %{onward_route: [address, "worker"], payload: "hello"}

Ockam.Router.route(message)

You don't need to explicitly create client in that case.

We're thinking of refactoring this API as it's not that intuitive.
If you want to manage your client explicitly (which is not recommended), you don't need this option, but you cannot use the TCPAddress in that case (as it's redundant):

Ockam.Transport.TCP.Listener.create(ip: {127,0,0,1}, port: 4000)

{:ok, client_address} = Ockam.Transport.TCP.Client.create(destination: %{ip: {127,0,0,1}, port: 4000})

OckamPoc.Worker.create(address: "worker")

message = %{onward_route: [client_address, "worker"], payload: "hello"}

Ockam.Router.route(message)