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DragonBot Ticket Close Hang

Sat, 10 Oct 2026 18:25:00 +0800

Context

DragonBot is a customer-support ticket bot for a purchasing-agent business on Discord, written with discord.py.

A customer opens a ticket, which is a private channel visible only to the customer and staff.
Every status change renames the channel to {type}-{id:04d}-{status}, so staff can see the status from the channel list.
Closing a ticket sets the status to CLOSED, exports the conversation with DiscordChatExporter, posts the transcript to an archive channel, and DMs the customer a feedback form.

What Happened

After a staff member confirmed closing a ticket, the bot sometimes sat on 「正在生成頻道紀錄以及傳送回饋單給顧客…」 for up to 10 minutes before the after-close buttons appeared. The owner reported it too.

LeetCodeBot: One Session, Many Commands

Fri, 28 Aug 2026 20:27:00 +0800

Context

LeetCodeBot talks to its database through AsyncDatabaseManager, an async context manager that hands out SQLAlchemy sessions:

async with self.async_database_manager as db:
 db.add(row)
# leaving the block commits, or rolls back on error

main.py creates one manager and shares it across every cog. The old version looked like this:

async def __aenter__(self) -> AsyncSession:
 self.session = self._sessionmaker()
 return self.session

async def __aexit__(self, exc_type, exc_val, exc_tb):
 try:
 assert self.session
 if exc_type:
 await self.session.rollback()
 else:
 await self.session.commit()
 await self.session.close()
 except AssertionError:
 return True
 finally:
 return False

It has two bugs (#38).

Bug 1: `aexit` commits the wrong session

__aenter__ returns a new session, so the caller’s db is bound to that object. But __aexit__ reads self.session, which belongs to the shared manager.

LeetCodeBot: The Bug the Async Migration Did Not Write

Fri, 28 Aug 2026 20:27:00 +0800

Context

LeetCodeBot is a Discord bot for looking up and discussing LeetCode problems. It stores problems and their topic tags with SQLAlchemy on SQLite.

In August 2026, #35 moved the database layer from synchronous SQLAlchemy to async (sqlite+aiosqlite). The bot kept running in production afterwards, with no errors.

What happened

A fresh clone could not start the bot. Deleting the database file to “start clean” made it fail every time:

sqlalchemy.exc.MissingGreenlet: greenlet_spawn has not been called;
can't call await_only() here. Was IO attempted in an unexpected place?
File "core/leetcode_problem.py", line 420, in add_problem_to_db
if db_tag not in db_problem.tags:

The failing expression is a plain attribute read: db_problem.tags.

Python on Blog

DragonBot Ticket Close Hang

Context

What Happened

LeetCodeBot: One Session, Many Commands

Context

Bug 1: __aexit__ commits the wrong session

LeetCodeBot: The Bug the Async Migration Did Not Write

Context

What happened

Bug 1: `aexit` commits the wrong session