我正在尝试创建一个连接到VPN的Docker容器，然后检查它是否可以连接到某些数据库。目前我正在使用以下代码：
DB_URI_PREFIX = {
'mssql': 'mssql+pymssql://', 'oracle': 'oracle+cx_oracle://', 'postgres': 'postgres://',
}
def connect_to_db(db_type: str, host: str, username: str, password: str, database: str):
db_uri = '{}{}:{}@{}/{}'.format(DB_URI_PREFIX[db_type], username, password, host, database)
engine = create_engine(db_uri)
connection = engine.connect()
print('Successfully connected to {}/{}'.format(host, database))
connection.close()
db_uri对于SQL Server数据库最终为mssql+pymssql://user:pass@host:port_num/database_name，对于Oracle数据库最终为oracle+cx_oracle://user:pass@host:port_num/database_name。
以上适用于SQL Server和Postgres数据库，但对于Oracle数据库，我收到此错误：
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 2158, in _wrap_pool_connect
return fn()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 345, in unique_connection
return _ConnectionFairy._checkout(self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 782, in _checkout
fairy = _ConnectionRecord.checkout(pool)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 532, in checkout
rec = pool._do_get()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 1186, in _do_get
self._dec_overflow()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
compat.reraise(exc_type, exc_value, exc_tb)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/util/compat.py", line 187, in reraise
raise value
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 1183, in _do_get
return self._create_connection()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 350, in _create_connection
return _ConnectionRecord(self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 477, in __init__
self.__connect(first_connect_check=True)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 667, in __connect
connection = pool._invoke_creator(self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/strategies.py", line 105, in connect
return dialect.connect(*cargs, **cparams)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/default.py", line 410, in connect
return self.dbapi.connect(*cargs, **cparams)
cx_Oracle.DatabaseError: ORA-12545: Connect failed because target host or object does not exist
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "connect_to_db.py", line 37, in <module>
connect_to_db(args.db_type, args.host, args.username, args.password, args.database)
File "connect_to_db.py", line 16, in connect_to_db
connection = engine.connect()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 2102, in connect
return self._connection_cls(self, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 90, in __init__
if connection is not None else engine.raw_connection()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 2188, in raw_connection
self.pool.unique_connection, _connection)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 2162, in _wrap_pool_connect
e, dialect, self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 1476, in _handle_dbapi_exception_noconnection
exc_info
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/util/compat.py", line 186, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/base.py", line 2158, in _wrap_pool_connect
return fn()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 345, in unique_connection
return _ConnectionFairy._checkout(self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 782, in _checkout
fairy = _ConnectionRecord.checkout(pool)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 532, in checkout
rec = pool._do_get()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 1186, in _do_get
self._dec_overflow()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
compat.reraise(exc_type, exc_value, exc_tb)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/util/compat.py", line 187, in reraise
raise value
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 1183, in _do_get
return self._create_connection()
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 350, in _create_connection
return _ConnectionRecord(self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 477, in __init__
self.__connect(first_connect_check=True)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/pool.py", line 667, in __connect
connection = pool._invoke_creator(self)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/strategies.py", line 105, in connect
return dialect.connect(*cargs, **cparams)
File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/default.py", line 410, in connect
return self.dbapi.connect(*cargs, **cparams)
sqlalchemy.exc.DatabaseError: (cx_Oracle.DatabaseError) ORA-12545: Connect failed because target host or object does not exist (Background on this error at: http://sqlalche.me/e/4xp6)
最初我认为这意味着无法找到主机但是在ping它时它会响应。另外，奇怪的是，如果我使用cx_Oracle直接连接“Oracle风格”＆＃39;连接字符串并将其提供给SQLAlchemy，我可以连接：
def get_oracle_connection(conn_str: str):
return cx_Oracle.connect(conn_str)
def connect_to_db(host: str, username: str, password: str, database: str):
conn_str = '{}/{}@{}/{}'.format(username, password, host, database)
conn_creator = partial(get_oracle_connection, conn_str=conn_str)
engine = create_engine('oracle+cx_oracle://', creator=conn_creator)
connection = engine.connect()
print('Successfully connected to {}'.format(conn_str))
connection.close()
在这种情况下，conn_str将为user/pass@host/database_name。
在我的Docker容器中，我运行Python 3并使用openconnect连接到VPN。我还在容器中安装了Oracle instantclient。
requirements.txt：
SQLAlchemy==1.2.2
pymssql==2.1.3
cx-Oracle==6.1
psycopg2==2.7.4
我在这里某处犯了错误，或者这是SQLAlchemy的错误？
答案 0 :(得分：0)
失败的代码有'{}{}:{}@{}/{}'但是工作代码有'{}/{}@{}/{}'前者缺少用户名和密码之间的斜杠，并且不清楚端口号（冒号后）的设置位置。