baseimage-tutorial-framework/lib/tfw/components/pipe_io_event_handler.py

from abc import abstractmethod
from json import loads, dumps, JSONDecodeError

from tfw import EventHandlerBase
from tfw.config.logs import logging

from .pipe_io_server import PipeIOServer

LOG = logging.getLogger(__name__)


class PipeIOEventHandlerBase(EventHandlerBase):
    def __init__(self, key, in_pipe_path, out_pipe_path, permissions=0o600):
        super().__init__(key)
        self.pipe_io = CallbackPipeIOServer(
            in_pipe_path,
            out_pipe_path,
            self.handle_pipe_event,
            permissions
        )
        self.pipe_io.start()

    @abstractmethod
    def handle_pipe_event(self, message):
        raise NotImplementedError()

    def cleanup(self):
        self.pipe_io.stop()


class CallbackPipeIOServer(PipeIOServer):
    def __init__(self, in_pipe_path, out_pipe_path, callback, permissions):
        super().__init__(in_pipe_path, out_pipe_path, permissions)
        self.callback = callback

    def handle_message(self, message):
        self.callback(message)


class PipeIOEventHandler(PipeIOEventHandlerBase):
    def handle_event(self, message):
        try:
            json_bytes = dumps(message).encode()
            self.pipe_io.send_message(json_bytes)
        except TypeError:
            LOG.error("Message %s not JSON serializable! Ignoring...", message)

    def handle_pipe_event(self, message):
        try:
            json = loads(message)
            self.server_connector.send(json)
        except JSONDecodeError:
            LOG.error("Invalid JSON received on %s! Ignoring...", self.pipe_io.in_pipe)