Rework PipeIOServer to use "keep pipes open" model with robust unblocking

echo_server.py

@@ -12,7 +12,7 @@ if __name__ == "__main__":
     pipe_io = EchoPipeIOServer()
     signal(SIGTERM, lambda a, b: pipe_io.stop())
     signal(SIGINT, lambda a, b: pipe_io.stop())
-    pipe_io.run()
     print('Running pipe IO server with named pipes:')
     print(f'Input:  {pipe_io.in_pipe}')
     print(f'Output: {pipe_io.out_pipe}')
+    pipe_io.run()

pipe_io_server/pipe.py

@@ -16,11 +16,3 @@ class Pipe:
 
     def create(self):
         mkfifo(self.path)
-
-    def write(self, data):
-        with open(self.path, 'wb') as pipe:
-            pipe.write(data)
-
-    def read(self):
-        with open(self.path, 'rb') as pipe:
-            return pipe.read()

pipe_io_server/pipe_io_server.py

@@ -1,7 +1,7 @@
 from os.path import join
 from secrets import token_urlsafe
-from collections import namedtuple
 from abc import ABC, abstractmethod
+from threading import Event
 
 from .pipe_reader_thread import PipeReaderThread
 from .pipe_writer_thread import PipeWriterThread
@@ -11,9 +11,10 @@ from .pipe import Pipe
 class PipeIOServer(ABC):
     def __init__(self, in_pipe=None, out_pipe=None):
         self._in_pipe, self._out_pipe = in_pipe, out_pipe
-        self._io_threads = None
         self._create_pipes()
-        self._init_io_threads()
+        self._stop_event = Event()
+        self._reader_thread, self._writer_thread = self._create_io_threads()
+        self._io_threads = (self._reader_thread, self._writer_thread)
 
     def _create_pipes(self):
         if not self.in_pipe or not self.out_pipe:
@@ -31,28 +32,30 @@ class PipeIOServer(ABC):
     def out_pipe(self):
         return self._out_pipe
 
-    def _init_io_threads(self):
+    def _create_io_threads(self):
-        io_threads_dict = {
+        reader_thread = PipeReaderThread(self.in_pipe, self._stop_event, self.handle_message)
-            'reader': PipeReaderThread(self.in_pipe, self.handle_message),
+        writer_thread = PipeWriterThread(self.out_pipe, self._stop_event)
-            'writer': PipeWriterThread(self.out_pipe)
+        return reader_thread, writer_thread
-        }
-        IOThreadsTuple = namedtuple('IOThreadsTuple', sorted(io_threads_dict.keys()))
-        self._io_threads = IOThreadsTuple(**io_threads_dict)
 
     @abstractmethod
     def handle_message(self, message):
         raise NotImplementedError()
 
     def send(self, message):
-        self._io_threads.writer.write(message)
+        self._writer_thread.write(message)
 
     def run(self):
         for thread in self._io_threads:
             thread.start()
+        self._stop_event.wait()
+        self._stop()
 
     def stop(self):
+        self._stop_event.set()
+
+    def _stop(self):
         for thread in self._io_threads:
-            if thread.isAlive():
+            if thread.is_alive():
                 thread.stop()
         Pipe(self.in_pipe).remove()
         Pipe(self.out_pipe).remove()

pipe_io_server/pipe_reader_thread.py

@@ -1,25 +1,37 @@
+from contextlib import suppress
+from os import open as osopen
+from os import write, close, O_WRONLY, O_NONBLOCK
 from threading import Thread
 
 from .terminate_process_on_failure import terminate_process_on_failure
-from .pipe import Pipe
 
 
 class PipeReaderThread(Thread):
-    _stop_sequence = b'stop_reading'
+    eof = ''
+    stop_sequence = 'stop_reading'
 
-    def __init__(self, pipe_path, message_handler):
+    def __init__(self, pipe_path, stop_event, message_handler):
         super().__init__()
         self._message_handler = message_handler
         self._pipe_path = pipe_path
+        self._stop_event = stop_event
 
     @terminate_process_on_failure
     def run(self):
-        while True:
+        with open(self._pipe_path, 'r') as pipe:
-            message = Pipe(self._pipe_path).read()
+            while True:
-            if message == self._stop_sequence:
+                message = pipe.readline().rstrip()
-                break
+                if message in (self.eof, self.stop_sequence):
-            self._message_handler(message)
+                    self._stop_event.set()
+                    break
+                self._message_handler(message)
 
     def stop(self):
-        Pipe(self._pipe_path).write(self._stop_sequence)
+        self.unblock()
         self.join()
+
+    def unblock(self):
+        with suppress(OSError):
+            fd = osopen(self._pipe_path, O_WRONLY | O_NONBLOCK)
+            write(fd, f'{self.stop_sequence}\n'.encode())
+            close(fd)

pipe_io_server/pipe_writer_thread.py

@@ -2,13 +2,13 @@ from threading import Thread
 from queue import Queue
 
 from .terminate_process_on_failure import terminate_process_on_failure
-from .pipe import Pipe
 
 
 class PipeWriterThread(Thread):
-    def __init__(self, pipe_path):
+    def __init__(self, pipe_path, stop_event):
         super().__init__()
         self._pipe_path = pipe_path
+        self._stop_event = stop_event
         self._write_queue = Queue()
 
     def write(self, message):
@@ -16,12 +16,22 @@ class PipeWriterThread(Thread):
 
     @terminate_process_on_failure
     def run(self):
-        while True:
+        try:
-            message = self._write_queue.get(block=True)
+            with open(self._pipe_path, 'w') as pipe:
-            if message is None:
+                while True:
-                break
+                    message = self._write_queue.get(block=True)
-            Pipe(self._pipe_path).write(message)
+                    if message is None:
+                        self._stop_event.set()
+                        break
+                    pipe.write(f'{message}\n')
+                    pipe.flush()
+        except BrokenPipeError:
+            self._stop_event.set()
 
     def stop(self):
-        self._write_queue.put(None)
+        self.unblock()
         self.join()
+
+    def unblock(self):
+        self._write_queue.put(None)
+        open(self._pipe_path, 'r').close()