downloader: Fix and improve the stop mechanism, stop on SIGTERM

Allows for graceful shutdown

downloader/downloader/main.py

@@ -5,6 +5,7 @@ import hashlib
 import logging
 import os
 import random
+import signal
 import sys
 import uuid
 from base64 import b64encode
@@ -161,6 +162,11 @@ class StreamsManager(object):
 
 	def start_worker(self, stream):
 		"""Start a new worker for given stream"""
+		# it's possible for fetch_latest to call us after we've started stopping,
+		# in that case do nothing.
+		if self.stopping.is_set():
+			logging.info("Ignoring worker start as we are stopping")
+			return
 		url_time, url = self.latest_urls[stream]
 		worker = StreamWorker(self, stream, url, url_time)
 		self.stream_workers[stream].append(worker)
@@ -208,11 +214,12 @@ class StreamsManager(object):
 				self.MAX_WORKER_AGE - workers[-1].age()
 				for workers in self.stream_workers.values() if workers
 			] or [0]))
-			# wait until refresh triggered or next max age reached
 			logging.info("Next master playlist refresh in at most {} sec".format(time_to_next_max_age))
-			self.refresh_needed.wait(time_to_next_max_age)
-			self.refresh_needed.clear()
-			gevent.spawn(self.fetch_latest)
+			# wait until refresh triggered, next max age reached, or we're stopping (whichever happens first)
+			gevent.wait([self.stopping, self.refresh_needed], timeout=time_to_next_max_age, count=1)
+			if not self.stopping.is_set():
+				self.refresh_needed.clear()
+				gevent.spawn(self.fetch_latest)
 			# wait min retry interval with jitter, unless we're stopping
 			self.stopping.wait(jitter(self.FETCH_MIN_INTERVAL))
 		logging.info("Stopping workers")
@@ -507,5 +514,7 @@ class SegmentGetter(object):
 def main(channel, base_dir=".", qualities=""):
 	qualities = qualities.split(",") if qualities else []
 	manager = StreamsManager(channel, base_dir, qualities)
+	gevent.signal(signal.SIGTERM, manager.stop) # shut down on sigterm
 	logging.info("Starting up")
 	manager.run()
+	logging.info("Gracefully stopped")