[PATCH RESEND v3 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.

v3:
  - Simplify try and except statement (comment from Muhammad Rizki).

v2:
  * no changes *

Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 daemon/telegram/mailer/listener.py | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/daemon/telegram/mailer/listener.py b/daemon/telegram/mailer/listener.py
index 1c92f23..46ccf93 100644
--- a/daemon/telegram/mailer/listener.py
+++ b/daemon/telegram/mailer/listener.py
@@ -5,6 +5,7 @@
 #
 
 from pyrogram.types import Message
+from mysql.connector.errors import OperationalError, DatabaseError
 from apscheduler.schedulers.asyncio import AsyncIOScheduler
 from telegram.packages import DaemonClient
 from atom import Scraper
@@ -43,13 +44,33 @@ 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 (OperationalError, DatabaseError) as e:
+			await self.handle_db_error(e)
+		except:
+			print(traceback.format_exc())
 
 		if not self.isRunnerFixed:
 			self.isRunnerFixed = True
-- 
Ammar Faizi