MySQL connector throws OperationalError about unavailable connection in Python Telegram bot after hours of running

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1

I’m building a Telegram bot using Python with the pyrogram framework. The bot connects to a MySQL database during startup like this:

bot = Client("telegram_bot", api_id=settings.API_ID, api_hash=settings.API_HASH,
             bot_token=settings.BOT_TOKEN, parse_mode=enums.ParseMode.DEFAULT)
with bot:
    try:
        db_connection = mysql.connector.connect(host="localhost", user=settings.DB_USER,
                                           password=settings.DB_PASS, database=settings.DB_NAME)
    except Exception as error:
        print(f'Database Error: {error}')
        exit()

I have a message handler that looks like this:

@bot.on_message(filters.private & filters.text & filters.user(settings.ADMIN_LIST))
async def processAdminMessage(client: Client, msg: types.Message):
    content = msg.text.lower()
    sender_id = msg.from_user.id
    conversation_id = msg.chat.id
    message_id = msg.id
    if content == 'count':
        cursor = db_connection.cursor(buffered=True)
        cursor.execute('SELECT COUNT(*) FROM members')
        data = cursor.fetchone()
        if not data:
            data = [0]
        cursor.close()
        response = f'Total members: {data[0]}'
        await msg.reply(response, reply_to_message_id=message_id)
        return

The bot works fine when I run it normally. However, when I start it with nohup python bot.py & and let it run for several hours, I get this error:

File "/path/to/mysql/connector/connection_cext.py", line 772, in cursor
    raise OperationalError("MySQL Connection not available.")
mysql.connector.errors.OperationalError: MySQL Connection not available.

Why does this happen? Does MySQL automatically close connections after some time? How can I fix this issue?

2

MySQL’s wait_timeout parameter is typically set to 8 hours, which means idle connections are closed automatically. In your case, the connection remains open but can become stale if it’s not actively used during that time, leading to the OperationalError. A recommended solution is to implement connection pooling or to periodically verify if the connection is still active with db_connection.is_connected() before executing any queries. If it returns False, simply reconnect to the database. You might also consider setting autocommit=True and use_unicode=True in your connection options, and if you’re using SQLAlchemy, adding pool_recycle=3600 to refresh connections every hour can help prevent this issue.

3

Had the same issue when I deployed my bot. MySQL drops inactive connections after 8 hours by default. Your connection dies but Python doesn’t know until you try using it.

I fixed this by ditching the global connection. Instead, I made a simple get_db_connection() function that creates a fresh connection each time, then closes it after the query runs. Yeah, there’s a tiny performance hit, but it’s way more reliable for bots that run 24/7.

You could check db_connection.is_connected() before each query and reconnect if it’s dead, but the fresh connection approach works better. I’ve used it on several Telegram bots without issues.

4

same thing happened to me too. mysql drops idle connections when they timeout. quick fix: call db_connection.ping(reconnect=True) before using your cursor - it’ll reconnect automatically if the connection died. better solution is using a connection pooling library instead of keeping one persistent connection.