带有pymssql的Python / Flask / sqlAlchemy环境中的Adaptive Server连接失败错误

Question

Update: I've confirmed this is only a problem when using an Azure SQL instance. I can use the same conn string to connect to local, network, and remote SQL (AWS) instances - it is only failing when connecting to Azure. I can connect to the Azure instance with other tools, like Management Studio.

I am building a small Python(3.4.x)/Flask application. I'm a complete noob here so forgive me if I break any rules in posting.

I have created the database engine with:

from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine('mssql+pymssql://dbadmin:dbadminpass@somedomain.server.net/databasename?charset=utf8')
db_session = scoped_session(sessionmaker(autocommit = False, autoflush = False, bind = engine))

Base = declarative_base()
Base.query = db_session.query_property()

def init_db():
    import models
    Base.metadata.creat_all(bind=engine)

Everything builds/interprets correctly at runtime but I get an error on running the query:

usr = User.query.filter_by(username=form.user.data).first()

The error is:

sqlalchemy.exc.OperationalError: (OperationalError) (20002, b'DB-Lib error message 20002, severity 9:\nAdaptive Server connection failed\n') None None

packages are: Flask==0.10.1, pymssql==2.1.1, SQLAlchemy==0.9.8

Thanks in advance.

Answer 1

I had similar problem and solved it by explicitly setting tds version = 7.0 . FreeTDS reads the user's ${HOME}/.freetds.conf before resorting to the system-wide sysconfdir/freetds.conf . So, I created ~/.freetds.conf with [global] section as:

[global]
tds version = 7.0

You can find more information on freetds.con : http://www.freetds.org/userguide/freetdsconf.htm

Answer 2

As I just had the same problem.

Since I could get pymssql to connect bypassing sqlalchemy , I figured everything else should be fine, so I used the create_engine parameter connect_args to pass everything straight to pymssql.connect .

server_name = "sql_server_name"
server_addres = server_name + ".database.windows.net"
database = "database_name"
username = "{}@{}".format("my_username", server_name)
password = "strong_password"

arguments = dict(server=server_addres, user=username,
                                 password=password, database=database, charset="utf8")

AZURE_ENGINE = create_engine('mssql+pymssql:///', connect_args=arguments)

This works fine and does not require one to meddle with the .freetds.conf file at all.

Also, note that pymssql requires usernname to be in the form username@servername . For more information see the linked documentation.