pipe-io-server/pipe_io_server.py

from threading import Thread
from queue import Queue
from os import mkfifo, remove, getpid, kill
from os.path import exists, join
from signal import SIGTERM
from secrets import token_urlsafe
from collections import namedtuple
from abc import ABC, abstractmethod
from traceback import print_exc


class PipeWriterThread(Thread):
    def __init__(self, pipe_path):
        super().__init__()
        self._pipe_path = pipe_path
        self._write_queue = Queue()

    def write(self, message):
        self._write_queue.put(message, block=True)

    def run(self):
        while True:
            message = self._write_queue.get(block=True)
            if message is None:
                break
            with open(self._pipe_path, 'wb') as pipe:
                pipe.write(message)

    def stop(self):
        self._write_queue.put(None)
        self.join()


class PipeReaderThread(Thread):
    _stop_sequence = b'stop_reading'

    def __init__(self, pipe_path, message_handler):
        super().__init__()
        self._message_handler = message_handler
        self._pipe_path = pipe_path

    def run(self):
        while True:
            with open(self._pipe_path, 'rb') as pipe:
                message = pipe.read()
            if message == self._stop_sequence:
                break
            try:
                self._message_handler(message)
            except:  # pylint: disable=bare-except
                print_exc()
                kill(getpid(), SIGTERM)

    def stop(self):
        with open(self._pipe_path, 'wb') as pipe:
            pipe.write(self._stop_sequence)
        self.join()


class PipeHandler:
    def __init__(self, *pipe_paths):
        self._pipe_paths = pipe_paths

    def recreate(self):
        self.remove()
        for pipe_path in self._pipe_paths:
            mkfifo(pipe_path)

    def remove(self):
        for pipe_path in self._pipe_paths:
            if exists(pipe_path):
                remove(pipe_path)


class PipeIOServer(ABC):
    def __init__(self, in_pipe=None, out_pipe=None):
        self.in_pipe, self.out_pipe = in_pipe, out_pipe
        self._create_pipes()

        io_threads_dict = {
            'reader': PipeReaderThread(self.in_pipe, self._handle_message),
            'writer': PipeWriterThread(self.out_pipe)
        }
        IOThreadsTuple = namedtuple('IOThreadsTuple', sorted(io_threads_dict.keys()))
        self._io_threads = IOThreadsTuple(**io_threads_dict)

    def _create_pipes(self):
        if not self.in_pipe or not self.out_pipe:
            pipe_id = token_urlsafe(6)
            self.in_pipe = join('/tmp', f'in_pipe_{pipe_id}')
            self.out_pipe = join('/tmp', f'out_pipe_{pipe_id}')
        PipeHandler(self.in_pipe, self.out_pipe).recreate()

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

    def send(self, message):
        self._io_threads.writer.write(message)

    def run(self):
        for thread in self._io_threads:
            thread.start()

    def stop(self):
        for thread in self._io_threads:
            thread.stop()
        PipeHandler(self.in_pipe, self.out_pipe).remove()