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

import logging
from abc import abstractmethod
from json import loads, dumps
from subprocess import run, PIPE, Popen
from functools import partial
from os import getpgid, killpg
from os.path import join
from signal import SIGTERM
from secrets import token_urlsafe
from threading import Thread
from contextlib import suppress

from tfw.event_handlers import EventHandlerBase

from .pipe_io_server import PipeIOServer, terminate_process_on_failure

LOG = logging.getLogger(__name__)
DEFAULT_PERMISSIONS = 0o600


class PipeIOEventHandlerBase(EventHandlerBase):
    def __init__(self, key, in_pipe_path, out_pipe_path, permissions=DEFAULT_PERMISSIONS):
        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_bytes):
        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):
        try:
            self.callback(message)
        except:  # pylint: disable=bare-except
            LOG.exception('Failed to handle message %s from pipe %s!', message, self.in_pipe)


class PipeIOEventHandler(PipeIOEventHandlerBase):
    def handle_event(self, message):
        json_bytes = dumps(message).encode()
        self.pipe_io.send_message(json_bytes)

    def handle_pipe_event(self, message_bytes):
        json = loads(message_bytes)
        self.send_message(json)


class TransformerPipeIOEventHandler(PipeIOEventHandlerBase):
    # pylint: disable=too-many-arguments
    def __init__(
            self, key, in_pipe_path, out_pipe_path,
            transform_in_cmd, transform_out_cmd,
            permissions=DEFAULT_PERMISSIONS
    ):
        self._transform_in = partial(self._transform_message, transform_in_cmd)
        self._transform_out = partial(self._transform_message, transform_out_cmd)
        super().__init__(key, in_pipe_path, out_pipe_path, permissions)

    @staticmethod
    def _transform_message(transform_cmd, message):
        proc = run(
            transform_cmd,
            input=message,
            stdout=PIPE,
            stderr=PIPE,
            shell=True
        )
        if proc.returncode == 0:
            return proc.stdout
        raise ValueError(f'Transforming message {message} failed!')

    def handle_event(self, message):
        json_bytes = dumps(message).encode()
        transformed_bytes = self._transform_out(json_bytes)
        if transformed_bytes:
            self.pipe_io.send_message(transformed_bytes)

    def handle_pipe_event(self, message_bytes):
        transformed_bytes = self._transform_in(message_bytes)
        if transformed_bytes:
            json_message = loads(transformed_bytes)
            self.send_message(json_message)


class CommandEventHandler(PipeIOEventHandler):
    def __init__(self, key, command, permissions=DEFAULT_PERMISSIONS):
        super().__init__(
            key,
            self._generate_tempfilename(),
            self._generate_tempfilename(),
            permissions
        )

        self._proc_stdin = open(self.pipe_io.out_pipe, 'rb')
        self._proc_stdout = open(self.pipe_io.in_pipe, 'wb')
        self._proc = Popen(
            command, shell=True, executable='/bin/bash',
            stdin=self._proc_stdin, stdout=self._proc_stdout, stderr=PIPE,
            start_new_session=True
        )
        self._monitor_proc_thread = self._start_monitor_proc()

    def _generate_tempfilename(self):
        # pylint: disable=no-self-use
        random_filename = partial(token_urlsafe, 10)
        return join('/tmp', f'{type(self).__name__}.{random_filename()}')

    def _start_monitor_proc(self):
        thread = Thread(target=self._monitor_proc, daemon=True)
        thread.start()
        return thread

    @terminate_process_on_failure
    def _monitor_proc(self):
        return_code = self._proc.wait()
        if return_code == -int(SIGTERM):
            # supervisord asked the program to terminate, this is fine
            return
        if return_code != 0:
            _, stderr = self._proc.communicate()
            raise RuntimeError(f'Subprocess failed ({return_code})! Stderr:\n{stderr.decode()}')

    def cleanup(self):
        with suppress(ProcessLookupError):
            process_group_id = getpgid(self._proc.pid)
            killpg(process_group_id, SIGTERM)
            self._proc_stdin.close()
            self._proc_stdout.close()
        super().cleanup()