Snakepit.Adapter behaviour (snakepit v0.1.2)

Behaviour for implementing adapters in Snakepit.

Adapters define how to communicate with external processes (Python, Node.js, etc.) and what commands they support. This allows Snakepit to be truly generalized and support multiple ML frameworks or external systems.

Required Callbacks

  • executable_path/0 - Returns the path to the runtime executable (python3, node, etc.)
  • script_path/0 - Returns the path to the external script to execute
  • script_args/0 - Returns additional arguments for the script
  • supported_commands/0 - Returns list of commands this adapter supports
  • validate_command/2 - Validates a command and its arguments

Optional Callbacks

  • process_response/2 - Post-process responses from the external process
  • prepare_args/2 - Pre-process arguments before sending to external process

Example Implementation

defmodule MyApp.PythonMLAdapter do
  @behaviour Snakepit.Adapter

  def executable_path, do: System.find_executable("python3") || System.find_executable("python")
  def script_path, do: Path.join(:code.priv_dir(:my_app), "python/ml_bridge.py")
  def script_args, do: ["--mode", "pool-worker"]
  def supported_commands, do: ["predict", "train", "ping"]

  def validate_command("predict", args) do
    if Map.has_key?(args, :input), do: :ok, else: {:error, :missing_input}
  end
  def validate_command("ping", _args), do: :ok
  def validate_command(cmd, _), do: {:error, {:unsupported_command, cmd}}
end

Summary

Callbacks

Optional callback to get a command-specific timeout in milliseconds.

Returns the path to the runtime executable.

Optional callback to prepare arguments before sending to external process.

Optional callback to process responses from the external process.

Returns additional command-line arguments for the script.

Returns the path to the external script that will be executed.

Returns a list of commands that this adapter supports.

Validates that a command and its arguments are valid for this adapter.

Functions

Default implementation for command_timeout - returns 30 seconds.

Default implementation for prepare_args - just returns args as-is.

Default implementation for process_response - just returns the response as-is.

Callbacks

command_timeout(command, args)

(optional)
@callback command_timeout(command :: String.t(), args :: map()) :: pos_integer()

Optional callback to get a command-specific timeout in milliseconds.

This allows adapters to specify appropriate timeouts for different commands based on their expected execution time.

executable_path()

@callback executable_path() :: String.t()

Returns the path to the runtime executable.

This is the interpreter or runtime that will execute the script. Examples: "python3", "node", "ruby", "R", etc.

prepare_args(command, args)

(optional)
@callback prepare_args(command :: String.t(), args :: map()) :: map()

Optional callback to prepare arguments before sending to external process.

This allows adapters to transform arguments into the format expected by their external script.

process_response(command, response)

(optional)
@callback process_response(command :: String.t(), response :: term()) ::
  {:ok, term()} | {:error, term()}

Optional callback to process responses from the external process.

This allows adapters to transform or validate responses before they're returned to the caller.

script_args()

@callback script_args() :: [String.t()]

Returns additional command-line arguments for the script.

These arguments will be passed to the script when it's started. Common examples: ["--mode", "pool-worker"], ["--config", "prod"]

script_path()

@callback script_path() :: String.t()

Returns the path to the external script that will be executed.

This should be an absolute path to a script that implements the bridge protocol for communication with Snakepit.

supported_commands()

@callback supported_commands() :: [String.t()]

Returns a list of commands that this adapter supports.

This is used for validation and documentation purposes.

validate_command(command, args)

@callback validate_command(command :: String.t(), args :: map()) :: :ok | {:error, term()}

Validates that a command and its arguments are valid for this adapter.

Returns :ok if valid, {:error, reason} if invalid.

Functions

default_command_timeout(command, args)

Default implementation for command_timeout - returns 30 seconds.

default_prepare_args(command, args)

Default implementation for prepare_args - just returns args as-is.

default_process_response(command, response)

Default implementation for process_response - just returns the response as-is.