[PATCH v2 2/2] daemon: telegram: Handle MySQL error

[Ammar Faizi <ammarfaizi2@gnuweeb.org>]

A previous patch creates a mechanism to allow the caller to reconnect
to the database by calling db.connect(). Handle MySQL error in the
main daemon loop path. Do reconnect to the database if such an error
happens. This way, the daemon can automatically recover from the MySQL
server restart without having the user restart the daemon.

Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 daemon/telegram/mailer/listener.py | 31 ++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/daemon/telegram/mailer/listener.py b/daemon/telegram/mailer/listener.py
index 1c92f23..4b48e21 100644
--- a/daemon/telegram/mailer/listener.py
+++ b/daemon/telegram/mailer/listener.py
@@ -7,6 +7,7 @@
 from pyrogram.types import Message
 from apscheduler.schedulers.asyncio import AsyncIOScheduler
 from telegram.packages import DaemonClient
+from mysql import connector
 from atom import Scraper
 from atom import utils
 from enums import Platform
@@ -43,13 +44,35 @@ class Bot():
 		)
 
 
+	async def handle_db_error(self, e):
+		#
+		# TODO(ammarfaizi2):
+		# Ideally, we also want to log and report this situation.
+		#
+		print(f"Database error: {str(e)}")
+		print("Reconnecting to the database...")
+
+		#
+		# Don't do this too often to avoid reconnect burst.
+		#
+		delay_in_secs = 3
+		reconnect_attempts = 3
+
+		self.db.ping(reconnect=True, attempts=reconnect_attempts,
+			     delay=delay_in_secs)
+
+
 	async def __run(self):
 		print("[__run]: Running...")
-		for url in self.db.get_atom_urls():
-			try:
+		try:
+			for url in self.db.get_atom_urls():
 				await self.__handle_atom_url(url)
-			except:
-				print(traceback.format_exc())
+		except connector.errors.OperationalError as e:
+			await self.handle_db_error(e)
+		except connector.errors.DatabaseError as e:
+			await self.handle_db_error(e)
+		except:
+			print(traceback.format_exc())
 
 		if not self.isRunnerFixed:
 			self.isRunnerFixed = True
-- 
Ammar Faizi