Refactor cleanup code

- Run the cleanup code on exceptions (e.g. ^C). There were several effects of that not happening previously; most notably, the log file was not written to the meta WARC.
- Cancel remaining tasks, which avoids a pile of asyncio warnings and errors on crashes.
- Close the DB before the WARC, or rather, close the WARC last. This is mostly a semantic change to further ensure that the log written to the meta WARC is as complete as possible.

qwarc/__init__.py

@@ -208,6 +208,11 @@ class Item:
 		return f'<{type(self).__module__}.{type(self).__name__} object {id(self)}, itemType = {self.itemType!r}, itemValue = {self.itemValue!r}>'
 
 
+# QWARC._closed values
+_STATE_RUNNING = 1
+_STATE_CLOSING = 2
+_STATE_CLOSED = 3
+
 class QWARC:
 	def __init__(self, itemClasses, warcBasePath, dbPath, command, specFile, specDependencies, logFilename, concurrency = 1, memoryLimit = 0, minFreeDisk = 0, warcSizeLimit = 0, warcDedupe = False):
 		'''
@@ -248,6 +253,7 @@ class QWARC:
 		self._sessions = [] # aiohttp.ClientSession instances
 		self._freeSessions = collections.deque() # ClientSession instances that are currently free
 		self._warc = None
+		self._closed = _STATE_CLOSED
 
 	@contextlib.asynccontextmanager
 	async def exclusive_db_lock(self):
@@ -317,6 +323,8 @@ class QWARC:
 					cursor.executemany('INSERT OR IGNORE INTO items (type, value, status) VALUES (?, ?, ?)', values)
 
 	async def run(self, loop):
+		self._closed = _STATE_RUNNING
+
 		for i in range(self._concurrency):
 			session = _aiohttp.ClientSession(
 			  connector = qwarc.aiohttp.TCPConnector(loop = loop),
@@ -355,6 +363,9 @@ class QWARC:
 				while len(self._tasks) >= self._concurrency:
 					await self._wait_for_free_task()
 
+				if self._closed == _STATE_CLOSING:
+					break
+
 				if os.path.exists('STOP'):
 					logging.info('Gracefully shutting down due to STOP file')
 					break
@@ -413,15 +424,11 @@ class QWARC:
 			for task in self._tasks:
 				task.cancel()
 			await asyncio.wait(self._tasks, return_when = concurrent.futures.ALL_COMPLETED)
+			self._tasks.clear()
 
 			raise
 		finally:
-			for session in self._sessions:
-				session.close()
-			self._warc.close()
-			self._db.close()
-
-			self._reset_working_vars()
+			await self.close()
 
 	async def flush_subitems(self, item):
 		await self._insert_subitems(item)
@@ -439,3 +446,22 @@ class QWARC:
 			if not values:
 				break
 			cursor.executemany('INSERT OR IGNORE INTO items (type, value, status) VALUES (?, ?, ?)', values)
+
+	async def close(self):
+		if self._closed in (_STATE_CLOSING, _STATE_CLOSED):
+			return
+
+		self._closed = _STATE_CLOSING
+
+		if self._tasks:
+			logger.warning(f'Cancelling {len(self._tasks)} task(s) remaining on cleanup')
+			for task in self._tasks:
+				task.cancel()
+			await asyncio.wait(self._tasks, return_when = concurrent.futures.ALL_COMPLETED)
+			self._tasks.clear()
+		self._db.close()
+		for session in self._sessions:
+			session.close()
+		self._warc.close()
+
+		self._reset_working_vars() # Also resets self._closed

qwarc/cli.py

@@ -83,4 +83,6 @@ def main():
 		loop.run_until_complete(a.run(loop))
 	except (Exception, KeyboardInterrupt) as e:
 		logging.exception('Unhandled error')
+	finally:
+		loop.run_until_complete(a.close())
 	loop.close()