PipeLogger: non-blocking write to pipe (bug 709746)

Add support to write to a non-blocking pipe instead of a
log file. This is needed for the purposes of bug 709746,
where PipeLogger will write to a pipe that is drained
by anoher PipeLogger instance which is running in the same
process.

Bug: https://bugs.gentoo.org/709746
Signed-off-by: Zac Medico <zmedico@gentoo.org>

lib/portage/tests/process/test_PopenProcess.py

@@ -9,6 +9,8 @@
 from portage.util._async.PipeLogger import PipeLogger
 from portage.util._async.PopenProcess import PopenProcess
 from portage.util._eventloop.global_event_loop import global_event_loop
+from portage.util.futures._asyncio.streams import _reader
+from portage.util.futures.compat_coroutine import coroutine, coroutine_return
 from _emerge.PipeReader import PipeReader
 
 class PopenPipeTestCase(TestCase):
@@ -73,8 +75,41 @@ def _testPipeLogger(self, test_string):
 
 		return content.decode('ascii', 'replace')
 
+	@coroutine
+	def _testPipeLoggerToPipe(self, test_string, loop=None):
+		"""
+		Test PipeLogger writing to a pipe connected to a PipeReader.
+		This verifies that PipeLogger does not deadlock when writing
+		to a pipe that's drained by a PipeReader running in the same
+		process (requires non-blocking write).
+		"""
+
+		producer = PopenProcess(proc=subprocess.Popen(
+			["bash", "-c", self._echo_cmd % test_string],
+			stdout=subprocess.PIPE, stderr=subprocess.STDOUT),
+			scheduler=loop)
+
+		pr, pw = os.pipe()
+
+		consumer = producer.pipe_reader = PipeLogger(background=True,
+			input_fd=producer.proc.stdout,
+			log_file_path=os.fdopen(pw, 'wb', 0))
+
+		reader = _reader(pr, loop=loop)
+		yield producer.async_start()
+		content = yield reader
+		yield producer.async_wait()
+		yield consumer.async_wait()
+
+		self.assertEqual(producer.returncode, os.EX_OK)
+		self.assertEqual(consumer.returncode, os.EX_OK)
+
+		coroutine_return(content.decode('ascii', 'replace'))
+
 	def testPopenPipe(self):
-		for x in (1, 2, 5, 6, 7, 8, 2**5, 2**10, 2**12, 2**13, 2**14):
+		loop = global_event_loop()
+
+		for x in (1, 2, 5, 6, 7, 8, 2**5, 2**10, 2**12, 2**13, 2**14, 2**15, 2**16):
 			test_string = x * "a"
 			output = self._testPipeReader(test_string)
 			self.assertEqual(test_string, output,
@@ -83,3 +118,7 @@ def testPopenPipe(self):
 			output = self._testPipeLogger(test_string)
 			self.assertEqual(test_string, output,
 				"x = %s, len(output) = %s" % (x, len(output)))
+
+			output = loop.run_until_complete(self._testPipeLoggerToPipe(test_string, loop=loop))
+			self.assertEqual(test_string, output,
+				"x = %s, len(output) = %s" % (x, len(output)))

lib/portage/util/_async/PipeLogger.py

@@ -8,6 +8,9 @@
 
 import portage
 from portage import os, _encodings, _unicode_encode
+from portage.util.futures import asyncio
+from portage.util.futures.compat_coroutine import coroutine
+from portage.util.futures.unix_events import _set_nonblocking
 from _emerge.AbstractPollTask import AbstractPollTask
 
 class PipeLogger(AbstractPollTask):
@@ -21,13 +24,15 @@ class PipeLogger(AbstractPollTask):
 	"""
 
 	__slots__ = ("input_fd", "log_file_path", "stdout_fd") + \
-		("_log_file", "_log_file_real")
+		("_io_loop_task", "_log_file", "_log_file_real")
 
 	def _start(self):
 
 		log_file_path = self.log_file_path
-		if log_file_path is not None:
-
+		if hasattr(log_file_path, 'write'):
+			self._log_file = log_file_path
+			_set_nonblocking(self._log_file.fileno())
+		elif log_file_path is not None:
 			self._log_file = open(_unicode_encode(log_file_path,
 				encoding=_encodings['fs'], errors='strict'), mode='ab')
 			if log_file_path.endswith('.gz'):
@@ -57,16 +62,17 @@ def _start(self):
 				fcntl.fcntl(fd, fcntl.F_SETFD,
 					fcntl.fcntl(fd, fcntl.F_GETFD) | fcntl.FD_CLOEXEC)
 
-		self.scheduler.add_reader(fd, self._output_handler, fd)
+		self._io_loop_task = asyncio.ensure_future(self._io_loop(fd), loop=self.scheduler)
+		self._io_loop_task.add_done_callback(self._io_loop_done)
 		self._registered = True
 
 	def _cancel(self):
 		self._unregister()
 		if self.returncode is None:
 			self.returncode = self._cancelled_returncode
 
-	def _output_handler(self, fd):
-
+	@coroutine
+	def _io_loop(self, fd):
 		background = self.background
 		stdout_fd = self.stdout_fd
 		log_file = self._log_file 
@@ -76,14 +82,18 @@ def _output_handler(self, fd):
 
 			if buf is None:
 				# not a POLLIN event, EAGAIN, etc...
-				break
+				future = self.scheduler.create_future()
+				self.scheduler.add_reader(fd, future.set_result, None)
+				try:
+					yield future
+				finally:
+					self.scheduler.remove_reader(fd)
+					future.done() or future.cancel()
+				continue
 
 			if not buf:
 				# EOF
-				self._unregister()
-				self.returncode = self.returncode or os.EX_OK
-				self._async_wait()
-				break
+				return
 
 			else:
 				if not background and stdout_fd is not None:
@@ -120,8 +130,34 @@ def _output_handler(self, fd):
 								fcntl.F_GETFL) ^ os.O_NONBLOCK)
 
 				if log_file is not None:
-					log_file.write(buf)
-					log_file.flush()
+					write_buf = buf
+					while True:
+						try:
+							if write_buf is not None:
+								log_file.write(write_buf)
+								write_buf = None
+							log_file.flush()
+						except EnvironmentError as e:
+							if e.errno != errno.EAGAIN:
+								raise
+							future = self.scheduler.create_future()
+							self.scheduler.add_writer(self._log_file.fileno(), future.set_result, None)
+							try:
+								yield future
+							finally:
+								self.scheduler.remove_writer(self._log_file.fileno())
+								future.done() or future.cancel()
+						else:
+							break
+
+	def _io_loop_done(self, future):
+		try:
+			future.result()
+		except asyncio.CancelledError:
+			self.cancel()
+			self._was_cancelled()
+		self.returncode = self.returncode or os.EX_OK
+		self._async_wait()
 
 	def _unregister(self):
 		if self.input_fd is not None:
@@ -133,11 +169,16 @@ def _unregister(self):
 				self.input_fd.close()
 			self.input_fd = None
 
+		if self._io_loop_task is not None:
+			self._io_loop_task.done() or self._io_loop_task.cancel()
+			self._io_loop_task = None
+
 		if self.stdout_fd is not None:
 			os.close(self.stdout_fd)
 			self.stdout_fd = None
 
 		if self._log_file is not None:
+			self.scheduler.remove_writer(self._log_file.fileno())
 			self._log_file.close()
 			self._log_file = None