PollScheduler: timeouts regardless of IO events

Now PollScheduler will execute timeouts predictably, even when there
no IO events being generated. This allows the Scheduler's display
updates to be handled via timeout_add.

3 files changed, 59 insertions, 56 deletions

diff --git a/pym/_emerge/JobStatusDisplay.py b/pym/_emerge/JobStatusDisplay.py
index 877a0c963..d84d1b060 100644
--- a/pym/_emerge/JobStatusDisplay.py
+++ b/pym/_emerge/JobStatusDisplay.py
@@ -209,24 +209,26 @@ class JobStatusDisplay(object):
 	def display(self):
 		"""
 		Display status on stdout, but only if something has
-		changed since the last call.
+		changed since the last call. This always returns True,
+		for continuous scheduling via timeout_add.
 		"""
 
 		if self.quiet:
-			return
+			return True
 
 		current_time = time.time()
 		time_delta = current_time - self._last_display_time
 		if self._displayed and \
 			not self._changed:
 			if not self._isatty:
-				return
+				return True
 			if time_delta < self._min_display_latency:
-				return
+				return True
 
 		self._last_display_time = current_time
 		self._changed = False
 		self._display_status()
+		return True
 
 	def _display_status(self):
 		# Don't use len(self._completed_tasks) here since that also
diff --git a/pym/_emerge/PollScheduler.py b/pym/_emerge/PollScheduler.py
index fd573592a..519a3700d 100644
--- a/pym/_emerge/PollScheduler.py
+++ b/pym/_emerge/PollScheduler.py
@@ -43,6 +43,7 @@ class PollScheduler(object):
 		# Increment id for each new handler.
 		self._event_handler_id = 0
 		self._timeout_handlers = {}
+		self._timeout_interval = None
 		self._poll_obj = create_poll_instance()
 		self._polling = False
 		self._scheduling = False
@@ -142,18 +143,51 @@ class PollScheduler(object):
 		return True
 
 	def _poll(self, timeout=None):
-		"""
-		All poll() calls pass through here. The poll events
-		are added directly to self._poll_event_queue.
-		In order to avoid endless blocking, this raises
-		StopIteration if timeout is None and there are
-		no file descriptors to poll.
-		"""
 		if self._polling:
 			return
 		self._polling = True
 		try:
-			self._do_poll(timeout=timeout)
+			if self._timeout_interval is None:
+				self._run_timeouts()
+				self._do_poll(timeout=timeout)
+
+			elif timeout is None:
+				while True:
+					self._run_timeouts()
+					previous_count = len(self._poll_event_queue)
+					self._do_poll(timeout=self._timeout_interval)
+					if previous_count != len(self._poll_event_queue):
+						break
+
+			elif timeout <= self._timeout_interval:
+				self._run_timeouts()
+				self._do_poll(timeout=timeout)
+
+			else:
+				remaining_timeout = timeout
+				start_time = time.time()
+				while True:
+					self._run_timeouts()
+					# _timeout_interval can change each time
+					# _run_timeouts is called
+					min_timeout = remaining_timeout
+					if self._timeout_interval is not None and \
+						self._timeout_interval < min_timeout:
+						min_timeout = self._timeout_interval
+
+					previous_count = len(self._poll_event_queue)
+					self._do_poll(timeout=min_timeout)
+					if previous_count != len(self._poll_event_queue):
+						break
+					elapsed_time = time.time() - start_time
+					if elapsed_time < 0:
+						# The system clock has changed such that start_time
+						# is now in the future, so just assume that the
+						# timeout has already elapsed.
+						break
+					remaining_timeout = timeout - 1000 * elapsed_time
+					if remaining_timeout <= 0:
+						break
 		finally:
 			self._polling = False
 
@@ -165,7 +199,6 @@ class PollScheduler(object):
 		StopIteration if timeout is None and there are
 		no file descriptors to poll.
 		"""
-		self._run_timeouts()
 		if not self._poll_event_handlers:
 			self._schedule()
 			if timeout is None and \
@@ -273,6 +306,8 @@ class PollScheduler(object):
 			self._timeout_handler_class(
 				interval=interval, function=function, args=args,
 				source_id=source_id, timestamp=time.time())
+		if self._timeout_interval is None or self._timeout_interval < interval:
+			self._timeout_interval = interval
 		return source_id
 
 	def _run_timeouts(self):
@@ -320,6 +355,12 @@ class PollScheduler(object):
 		"""
 		timeout_handler = self._timeout_handlers.pop(reg_id, None)
 		if timeout_handler is not None:
+			if timeout_handler.interval == self._timeout_interval:
+				if self._timeout_handlers:
+					self._timeout_interval = \
+						min(x.interval for x in self._timeout_handlers.values())
+				else:
+					self._timeout_interval = None
 			return True
 		f = self._poll_event_handler_ids.pop(reg_id, None)
 		if f is None:
diff --git a/pym/_emerge/Scheduler.py b/pym/_emerge/Scheduler.py
index 5b56650f3..e6f3e0e5c 100644
--- a/pym/_emerge/Scheduler.py
+++ b/pym/_emerge/Scheduler.py
@@ -196,6 +196,8 @@ class Scheduler(PollScheduler):
 
 		self._status_display = JobStatusDisplay(
 			xterm_titles=('notitles' not in settings.features))
+		self._timeout_add(self._max_display_latency,
+			self._status_display.display)
 		self._max_load = myopts.get("--load-average")
 		max_jobs = myopts.get("--jobs")
 		if max_jobs is None:
@@ -352,50 +354,8 @@ class Scheduler(PollScheduler):
 		gc.collect()
 
 	def _poll(self, timeout=None):
-
 		self._schedule()
-
-		if timeout is None:
-			while True:
-				if not self._poll_event_handlers:
-					self._schedule()
-					if not self._poll_event_handlers:
-						raise StopIteration(
-							"timeout is None and there are no poll() event handlers")
-				previous_count = len(self._poll_event_queue)
-				PollScheduler._poll(self, timeout=self._max_display_latency)
-				self._status_display.display()
-				if previous_count != len(self._poll_event_queue):
-					break
-
-		elif timeout <= self._max_display_latency:
-			PollScheduler._poll(self, timeout=timeout)
-			if timeout == 0:
-				# The display is updated by _schedule() above, so it would be
-				# redundant to update it here when timeout is 0.
-				pass
-			else:
-				self._status_display.display()
-
-		else:
-			remaining_timeout = timeout
-			start_time = time.time()
-			while True:
-				previous_count = len(self._poll_event_queue)
-				PollScheduler._poll(self,
-					timeout=min(self._max_display_latency, remaining_timeout))
-				self._status_display.display()
-				if previous_count != len(self._poll_event_queue):
-					break
-				elapsed_time = time.time() - start_time
-				if elapsed_time < 0:
-					# The system clock has changed such that start_time
-					# is now in the future, so just assume that the
-					# timeout has already elapsed.
-					break
-				remaining_timeout = timeout - 1000 * elapsed_time
-				if remaining_timeout <= 0:
-					break
+		PollScheduler._poll(self, timeout=timeout)
 
 	def _set_max_jobs(self, max_jobs):
 		self._max_jobs = max_jobs