Handle TCP Provider: Error code 0x68 (104)

Question

I'm using this code to sync my db with the clients:

    import pyodbc

    SYNC_FETCH_ARRAY_SIZE=25000

    # define connection + cursor
    connection = pyodbc.connect()
    cursor = connection.cursor()

    query = 'select some_columns from mytable'
    cursor.execute(query)

    while True:
        rows = cursor.fetchmany(SYNC_FETCH_ARRAY_SIZE) # <<< error here

        if not rows:
            break

        insert_to_our_db(rows)

    cursor.close()

I'm getting the below error intermitently:

File "....py", line 120, in ...
  rows = sg_cur.fetchmany(SYNC_FETCH_ARRAY_SIZE)
pyodbc.OperationalError: ('08S01', '[08S01] [Microsoft][ODBC Driver 17 for SQL Server]TCP Provider: Error code 0x68 (104) (SQLGetData)')

How should i handle this error? Is this an error on the connection (thus i need to close and recreate the connection) or on the cursor and i simply need to add a retry?

I will add the below to retry (in place of the line throwing the error), is this enough to solve the issue? Will retries have any effect at all if im experiencing a tcp error?

MAX_RETRIES=5

def get_rows(retry_count=0):
    """
    Wrapper function to add retry functionality to fetchmany
    """
    try:
        rows = sg_cur.fetchmany(SYNC_FETCH_ARRAY_SIZE)

    except Exception as e:
        if retry_count >= MAX_RETRIES:
            raise ConnectionError(f'fetchmany caused the error: {e}')

        else:
            logger.debug(f'Error in get_rows: {e}, attempt: {retry_count}/{MAX_RETRIES}')
            retry_count += 1
            return get_rows(retry_count=retry_count)

    return rows

Edit:

There is an issue open on github for this. In the meantime what would be a viable workaround?

• Store the last read after insert_to_our_db in our db then restart from there in case of a bug
• just run the entire process again

Notes:

• The error is intermittent, thus hard to test
• I'm syncing a large table from a client's db on a different host. Thus i need to update/insert all rows at once to be sure that the data is current
• I cant make changes to the client's db

Answer 1

try this:

sudo ifconfig eth0 mtu 1350

Answer 2

I realized that the table into which i was inserting wasn't indexed.

To add the rows i was running an upsert, to avoid duplication. Adding an index to the table fixed my issue.

Looking at other people who had this issue, this seems to be the accepted solution. I definitely should have had the table indexed anyway- lesson learned.

Edit. I'll leave this answer unaccepted in the hope that someone can shed more light on the issue. For me though, adding the index (which sped up the transaction) fixed the problem.

Answer 3

Setting pool related parameters helped:

engine = create_engine(
    sql_connection_string,
    echo=False,
    connect_args={
        "autocommit": False,
        "connect_timeout": 30,
    },
    pool_pre_ping=True,
    pool_size=25,
    pool_recycle=3600,
)