restreamer: Have playlist cache stream results

restreamer/restreamer/main.py

@@ -20,6 +20,7 @@ from common.flask_stats import request_stats, after_request
 from common.images import compose_thumbnail_template
 from common.segments import smart_cut_segments, feed_input, render_segments_waveform, extract_frame, list_segment_files, get_best_segments_for_frame
 from common.chat import get_batch_file_range, merge_messages
+from common.cached_iterator import CachedIterator
 
 from . import generate_hls
 
@@ -275,9 +276,8 @@ def generate_media_playlist(channel, quality):
 	if end - start > datetime.timedelta(hours=12) and ('start' not in request.args or 'end' not in request.args):
 		return "Implicit range may not be longer than 12 hours", 400
 
+	def _generate_media_playlist():
 		cache_key = (hours_path, start, end)
-	if cache_key in _media_playlist_cache:
-		return _media_playlist_cache[cache_key].get()
 
 		# get_best_segments requires start be before end, special case that as no segments
 		# (not an error because someone might ask for a specific start, no end, but we ended up with
@@ -288,19 +288,30 @@ def generate_media_playlist(channel, quality):
 			# Note the None to indicate there was a "hole" at both start and end
 			segments = [None]
 
+		if cache_key in _media_playlist_cache:
+			yield from _media_playlist_cache[cache_key].get()
+			return
+
 		result = gevent.event.AsyncResult()
 		try:
 			# Note we don't populate the cache until we're in the try block,
 			# so there is no point where an exception won't be transferred to the result.
 			_media_playlist_cache[cache_key] = result
-		playlist = "".join(generate_hls.generate_media(segments, os.path.join(app.static_url_path, channel, quality)))
+			iterator = CachedIterator(generate_hls.generate_media(segments, os.path.join(app.static_url_path, channel, quality)))
-		result.set(playlist)
+			# We set the result immediately so that everyone can start returning it.
+			# Multiple readers from the CachedIterator is safe.
+			result.set(iterator)
 		except BaseException as ex:
 			result.set_exception(ex)
 			raise
+
+		# send the whole response
+		yield from iterator
+
 		# Now we're done, remove the async result so a fresh request can start.
 		assert _media_playlist_cache.pop(cache_key) is result, "Got someone else's AsyncResult"
-	return playlist
+
+	return _generate_media_playlist()
 
 
 @app.route('/cut/<channel>/<quality>.ts')