如何在 sql 连接失败后重试 python？

Question

当 connection/write 数据库在 python 失败时重试的正确方法是什么？

我正在尝试使用此代码并且它一直有效，直到我重新启动我的 sql 服务器并且 python 尝试连接到它我得到 "retry after 30 sec" 10 次，间隔为 30 秒但是当 sql 服务器运行 agian 时，它不会重新连接。

编辑：它在 retry_count1 = 10 时重新连接，但在下一个循环计数器需要计数到 10 才能连接到 agian。

有谁知道为什么它不会重新连接？

 retry_flag1 = True
        retry_count1 = 0
        while retry_flag1 and retry_count1 < 10:
          try:
            cursor = cnxn.cursor()
            cursor.execute('SELECT too_id FROM [TTMM].[dbo].[Machines] WHERE MachineID = {}'.format (machineid,))
            too_id = cursor.fetchone()[0]
            cursor.execute('INSERT INTO [TTMM].[dbo].[{}](counter, effectively, too_id) VALUES ({},{},{})'.format (machineid, counter, effectively, too_id,))
            cnxn.commit()
            cursor.close()
            retry_flag1 = False
          except as e:
            print(e)
            print("Retry after 30 sec")
            retry_count1 = retry_count1 + 1
            time.sleep(30)

这是重新启动 sql 服务器后的控制台输出。

('08S01', '[08S01] [FreeTDS][SQL Server]Write to the server failed (20006) (SQLExecDirectW)')
Retry after 1 sec
('08S01', '[08S01] [FreeTDS][SQL Server]Communication link failure (0) (SQLExecDirectW)')
Retry after 1 sec
('08S01', '[08S01] [FreeTDS][SQL Server]Communication link failure (0) (SQLExecDirectW)')
Retry after 1 sec
141222 Cykel
('08S01', '[08S01] [FreeTDS][SQL Server]Communication link failure (0) (SQLExecDirectW)')
Retry after 1 sec
('08S01', '[08S01] [FreeTDS][SQL Server]Communication link failure (0) (SQLExecDirectW)')

Answer 1

我通过添加 cnxn.close 并创建新连接找到了解决方案。

    retry_flag = True
    retry_count = 0
    cursor = cnxn.cursor()
    while retry_flag and retry_count < 5:
        try:
            cursor.execute('SELECT too_id FROM [TTMM].[dbo].[Machines] WHERE MachineID = {}'.format (machineid,))
            too_id = cursor.fetchone()[0]
            cursor.execute('INSERT INTO [TTMM].[dbo].[{}](counter, effectively, too_id) VALUES ({},{},{})'.format (machineid, counter, effectively, too_id,))
            retry_flag = False
            print("Printed To DB - Counter = ", counter, ", Effectively = ", effectively, ", too_id = ", too_id,)

        except Exception as e:
            print (e)
            print ("Retry after 5 sec")
            retry_count = retry_count + 1
            cursor.close()
            cnxn.close()
            time.sleep(5)
            cnxn = pyodbc.connect('DRIVER=FreeTDS;SERVER=*;PORT=*;DATABASE=*;UID=*;PWD=*;TDS_Version=8.7;', autocommit=True)
            cursor = cnxn.cursor()

    cursor.close()

如何在 sql 连接失败后重试 python？

How to retry after sql connection failed in python?

python

sql

try-catch

pyodbc

except