Elixir Pods

Elixir Pods is a way of communication between Elixir and a service implemented in any programming language (pod). This service must adhere to a simple protocol (pod protocol) that uses standard and battle tested tools (stdin, stdout, bencode and json) for it's implementation.

The main inspiration for this is Babashka Pods.

Basically is a command line tool that has an infinite bucle (while true) that listen to commands in stdin and outputs the results in stdout.

Note how every component is fully customizable, so you can implement those with your own tools and configurations.

sequenceDiagram
    Pod Client->>+Pod Service: {:ok, "start"}
    Pod Service-->>-Pod Client: {:ok, os_pid}
    Pod Client->>+Pod Service: {:ok, {os_pid, "describe"}}
    Pod Service-->>-Pod Client: {:ok, description}
    Pod Client->>+Pod Service: {:ok, {os_pid, {"invoke", params}}}
    Pod Service-->>-Pod Client: {:ok, result}
    Pod Client->>+Pod Service: {:ok, {os_pid, "shutdown"}}
    Pod Service-->>-Pod Client: {:ok, "stop"}

Loading

Implementing a Pod

You can implement the pods with any technology and a simple Elixir wrapper to expose their API.

• artifacts: The directory where the external code executables will be stored.
• pod.ex: The main public api for the pod.
• manifest.ex: Some helper functions to have more information about the pod.

If you want to debug you can use standard tools such as stdin and stdout. In Unix systems you can access by using (1 stdout, 2 stderr).

  cat /proc/<pid>/fd/1

An Elixir Pod must follow some simple rules:

• An infinite function (while true).
• Reads from stdin (in streaming mode).
• Writes to stdout (success and errors) and stderr (exceptions).
• Follows Elixir Pods format.
• At least implements the describe and invoke operators.
• Encodes messages with bencode.
• Encodes payload with JSON.

Installation

If available in Hex, the package can be installed by adding pods to your list of dependencies in mix.exs:

def deps do
  [
    {:pods, "~> 1.0.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/pods.