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>

1 files changed, 54 insertions, 13 deletions

diff --git a/lib/portage/util/_async/PipeLogger.py b/lib/portage/util/_async/PipeLogger.py
index a4258f350..6b03988a1 100644
--- a/lib/portage/util/_async/PipeLogger.py
+++ b/lib/portage/util/_async/PipeLogger.py
@@ -8,6 +8,9 @@ import sys
 
 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'):
@@ -57,7 +62,8 @@ class PipeLogger(AbstractPollTask):
 				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):
@@ -65,8 +71,8 @@ class PipeLogger(AbstractPollTask):
 		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 @@ class PipeLogger(AbstractPollTask):
 
 			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 @@ class PipeLogger(AbstractPollTask):
 								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 @@ class PipeLogger(AbstractPollTask):
 				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