I don't have Oracle, but here's a complete runnable example using MySQL
(hopefully the formatting will survive this time):
import sqlalchemy as sa
import MySQLdb
# start with the wrong password to force a connection error
engine = sa.create_engine("mysql://user:wrong@db/db")
@sa.event.listens_for(engine, "do_connect")
def receive_do_connect(dialect, conn_rec, cargs, cparams):
print(f"---- do_connect ----")
print(f"cargs: {cargs}")
print(f"cparams: {cparams}")
try:
return MySQLdb.connect(**cparams)
except Exception as e:
print(f"EXCEPTION: {e}")
# Store the correct password in cparams for future connection
attempts
cparams["passwd"] = "correct"
return MySQLdb.connect(**cparams)
conn1 = engine.connect()
print(f"conn1: {conn1}")
conn2 = engine.connect()
print(f"conn2: {conn2}")
And here's the output:
---- do_connect ----
cargs: []
cparams: {'host': 'db', 'db': 'db', 'user': 'user', 'passwd': 'wrong',
'client_flag': 2}
EXCEPTION: (1045, "Access denied for user 'user'@'172.18.0.9' (using
password: YES)")
conn1: <sqlalchemy.engine.base.Connection object at 0x7fbd481b93d0>
---- do_connect ----
cargs: []
cparams: {'host': 'db', 'db': 'db', 'user': 'user', 'passwd': 'correct',
'client_flag': 2}
conn2: <sqlalchemy.engine.base.Connection object at 0x7fbd49499f10>
As you can hopefully see, the first connection attempt triggered an
exception. The correct password was then stored in cparams, and the next
time we called engine.connect(), the correct password was already passed in
and no exception was raised.
Simon
On Wed, Mar 23, 2022 at 4:36 AM Srinu Chp <chpsr...@gmail.com> wrote:
> Hello Simon,
>
> I tried your suggestion as POC:
>
> def setup_event_handlers(engine):
> @event.listens_for(engine, 'do_connect')
> def receive_do_connect(dialect, conn_rec, cargs, cparams):
> print("inside do_connect")
> print('password %s' % cparams['password'])
> try:
> print("inside try")
> return cx_Oracle.connect(*cargs, **cparams)
> except Exception as e:
> print("inside catch")
> cparams['password'] = "NewPassword"
> return cx_Oracle.connect(*cargs, **cparams)
>
> Every time except block is triggered even I set correct password in Except
> block. As per document once cparams password set it should pass new
> password for new request. Can you please suggest if I miss anything here?
>
> Regards,
> Pydi
>
> On Tuesday, March 22, 2022 at 9:33:57 AM UTC-7 Srinu Chp wrote:
>
>> Hello Simon,
>>
>> Thank you very much for detail information.
>>
>> Regards,
>> Pydi
>>
>> On Tuesday, March 22, 2022 at 3:11:34 AM UTC-7 Simon King wrote:
>>
>>> I don't know anything about Airflow. Are you sure that each of these
>>> tasks is running inside the same Python interpreter/process? I see
>>> Airflow can distribute tasks among workers:
>>>
>>> https://airflow.apache.org/docs/apache-airflow/stable/executor/index.html
>>>
>>> This sounds like a problem that is going to be very specific to your
>>> deployment environment. If you have multiple worker processes, you're
>>> going to need some way to distribute the new password to each of the
>>> workers (eg. a shared cache)
>>>
>>> But regardless of that, you're still not following the pattern from
>>> the documentation. I don't understand why you are creating a new
>>> engine inside your do_connect handler. You should be creating a
>>> cx-Oracle connection and returning it. The parameters passed to the
>>> do_connect handler have already been parsed out of the connection
>>> string. So for example, if your connection string includes a
>>> "password=some_password" parameter, then cparams will have a
>>> "password" key with the value "some_password". The same cparams
>>> dictionary will be passed to the do_connect handler each time, so if
>>> you mutate the dictionary (eg. by updating the "password" key), the
>>> next call to the handler will contain the new value.
>>>
>>> If each task invocation is creating a new engine using a connection
>>> string that is out of date, then none of that will help you, but that
>>> would be an Airflow problem, not an SQLAlchemy problem.
>>>
>>> Simon
>>>
>>> On Mon, Mar 21, 2022 at 8:27 PM Srinu Chp <chps...@gmail.com> wrote:
>>> >
>>> > Hello Simon,
>>> >
>>> > I tried POC approach in my project where we are using Airflow using
>>> sqlalchemy to connect to db. Here is the event code:
>>> >
>>> > @event.listens_for(engine, "do_connect")
>>> > def receive_do_connect(dialect, conn_rec, cargs, cparams):
>>> > global SQL_ALCHEMY_CONN
>>> > log.info("receive_do_connect called for user AIRFLOW.")
>>> > log.info("user details DB: {}".format(SQL_ALCHEMY_CONN))
>>> > # creating new engine to valide using cx_oracle driver
>>> > engine_new =
>>> create_engine(f'{SQL_ALCHEMY_CONN}/?encoding=UTF-8&nencoding=UTF-8',
>>> max_identifier_length=128)
>>> > try:
>>> > with engine_new.connect() as conn:
>>> > log.info(conn.scalar("select sysdate from dual"))
>>> > SQL_ALCHEMY_CONN = "testNew_try"
>>> > except Exception as e:
>>> > # check for invalid user/pwd error
>>> > if search('ORA-01017', str(e)):
>>> > log.info("receive_do_connect exception occurred during engine
>>> connection e: {}".format(e))
>>> > ...<connect to secret client and fetch new password>
>>> > //update with new password
>>> > SQL_ALCHEMY_CONN = "testNew_except"
>>> > # this log print new value with updated password
>>> > log.info("user details DB after update in except block:
>>> {}".format(SQL_ALCHEMY_CONN))
>>> > cparams['New password']
>>> >
>>> > global SQL_ALCHEMY_CONN value is set during initialization. Once
>>> password is rotated I am trying to update the SQL_ALCHEMY_CONN so that next
>>> request will not go in except block. Every time logs print old
>>> SQL_ALCHEMY_CONN value even value is update in except block.
>>> >
>>> > second approach:
>>> > I tried to set env variable in except block:
>>> > os.environ['AIRFLOW__CORE__SQL_ALCHEMY_CONN']
>>> > env variable also refer to old value even after updating in except
>>> block.
>>> >
>>> > Can you please suggestion?
>>> > Regards,
>>> > Pydi
>>> > On Monday, March 21, 2022 at 10:55:09 AM UTC-7 Srinu Chp wrote:
>>> >>
>>> >> Hello Simon,
>>> >>
>>> >> Perfect, working as expected in standalone POC. Thank you quick help
>>> >>
>>> >> Regards,
>>> >> Pydi
>>> >>
>>> >> On Monday, March 21, 2022 at 9:52:04 AM UTC-7 Simon King wrote:
>>> >>>
>>> >>> As suggested here:
>>> >>>
>>> >>>
>>> https://docs.sqlalchemy.org/en/14/core/engines.html#fully-replacing-the-dbapi-connect-function
>>> >>>
>>> >>> In your do_connect handler, rather than calling engine.connect(),
>>> you
>>> >>> need to call cx_Oracle.connect(), and return the result. You can
>>> wrap
>>> >>> this in an exception handler that detects the "incorrect password"
>>> >>> error to fetch new credentials. Something like this perhaps:
>>> >>>
>>> >>> @event.listens_for(engine, 'do_connect')
>>> >>> def receive_do_connect(dialect, conn_rec, cargs, cparams):
>>> >>> try:
>>> >>> return cx_Oracle.connect(*cargs, **cparams)
>>> >>> except <appropriate-cx-oracle-error>:
>>> >>> cparams["password"] = get_new_password()
>>> >>> return cx_Oracle.connect(*args, **cparams)
>>> >>>
>>> >>> Hope that helps,
>>> >>>
>>> >>> Simon
>>> >>>
>>> >>> On Mon, Mar 21, 2022 at 4:26 PM Srinu Chp <chps...@gmail.com>
>>> wrote:
>>> >>> >
>>> >>> > Hello Simon,
>>> >>> >
>>> >>> > Thank you for prompt response. I really appreciate your help. I am
>>> trying to achieve password rotation and we are using secret client to fetch
>>> new password. I tried do_connect event and fetch new password from secret
>>> client, working as expected but we are facing performance issue as we are
>>> every time connecting to secret client(3~5sec for each request). Instead I
>>> am trying to achieve if connect fails then fetch from secret client.
>>> >>> >
>>> >>> > I tried with handle_error event, when i get error check for
>>> invalid user/pwd and update session with latest engine. This approach also
>>> did not help
>>> >>> >
>>> >>> > Any insights are highly appreciated. Please suggest best approach.
>>> >>> >
>>> >>> > Regards,
>>> >>> > Pydi
>>> >>> > On Monday, March 21, 2022 at 2:22:04 AM UTC-7 Simon King wrote:
>>> >>> >>
>>> >>> >> I don't really understand what's going on in your code, but you
>>> seem
>>> >>> >> to be calling engine.connect() inside your "do_connect" event
>>> handler.
>>> >>> >> I would expect that to trigger another "do_connect" event, which
>>> in
>>> >>> >> turn will call engine.connect() again, which will trigger another
>>> >>> >> "do_connect" event, and so on. I'm surprised the application gets
>>> as
>>> >>> >> far as it does. Maybe the exception handler inside
>>> receive_do_connect
>>> >>> >> is allowing it to stumble on.
>>> >>> >>
>>> >>> >> Simon
>>> >>> >>
>>> >>> >> On Mon, Mar 21, 2022 at 4:51 AM Srinu Chp <chps...@gmail.com>
>>> wrote:
>>> >>> >> >
>>> >>> >> > Hello Team,
>>> >>> >> >
>>> >>> >> > I tried to create a standalone application POC for sqlalchemy
>>> to db connection. When I registered do_connect event, I see event is
>>> triggered couple of times for one call:
>>> >>> >> > sqlalchemy_connection.py
>>> >>> >> >
>>> >>> >> > import os
>>> >>> >> > import cx_Oracle
>>> >>> >> > from sqlalchemy import create_engine
>>> >>> >> > from sqlalchemy import event
>>> >>> >> >
>>> >>> >> > cx_Oracle.init_oracle_client(lib_dir=os.environ.get("HOME") +
>>> "/Downloads/instantclient_19_8")
>>> >>> >> > SQLALCHEMY_CONN = "test"
>>> >>> >> > count = 0
>>> >>> >> > engine = None
>>> >>> >> > def connect_db(pwd):
>>> >>> >> > global count
>>> >>> >> > global engine
>>> >>> >> > print(SQLALCHEMY_CONN)
>>> >>> >> > username = "ADMIN"
>>> >>> >> > password = pwd
>>> >>> >> > dsn = "pydidb_high"
>>> >>> >> > engine = create_engine(
>>> >>> >> > f'oracle://{username}:{password}@{dsn}/?encoding=UTF-8&nencoding=UTF-8',
>>> max_identifier_length=128)
>>> >>> >> > setup_event_handlers(engine)
>>> >>> >> >
>>> >>> >> > def setup_event_handlers(engine):
>>> >>> >> > @event.listens_for(engine, 'do_connect')
>>> >>> >> > def receive_do_connect(dialect, conn_rec, cargs, cparams):
>>> >>> >> > print("inside do_connect")
>>> >>> >> > global count
>>> >>> >> > try:
>>> >>> >> > with engine.connect() as conn:
>>> >>> >> > print("inside do_connect try block")
>>> >>> >> > print(conn.scalar("select sysdate from dual"))
>>> >>> >> > count += 2
>>> >>> >> > except Exception as e:
>>> >>> >> > print("inside do_connect except block")
>>> >>> >> > count += 1
>>> >>> >> >
>>> >>> >> > def db_connect_test():
>>> >>> >> > print(engine)
>>> >>> >> > with engine.connect() as conn:
>>> >>> >> > print(conn.scalar("select sysdate from dual"))
>>> >>> >> >
>>> >>> >> > gevent_sync.py
>>> >>> >> >
>>> >>> >> > import gevent
>>> >>> >> > import random
>>> >>> >> > import sqlalchemy_connection
>>> >>> >> >
>>> >>> >> > def task(pid):
>>> >>> >> > gevent.sleep(random.randint(0,2)*0.001)
>>> >>> >> > print('Task %s done' % pid)
>>> >>> >> > sqlalchemy_connection.connect_db(**********)
>>> >>> >> > sqlalchemy_connection.db_connect_test()
>>> >>> >> >
>>> >>> >> > def synchronous():
>>> >>> >> > for i in range(1,2):
>>> >>> >> > task(i)
>>> >>> >> > # sqlalchemy_connection.connect_db(**********)
>>> >>> >> >
>>> >>> >> > def asynchronous():
>>> >>> >> > threads = [gevent.spawn(task, i) for i in range(2)]
>>> >>> >> > gevent.joinall(threads)
>>> >>> >> >
>>> >>> >> > print('Synchronous:')
>>> >>> >> > synchronous()
>>> >>> >> > print('count %s ' % sqlalchemy_connection.count)
>>> >>> >> >
>>> >>> >> > # print('Asynchronous:')
>>> >>> >> > # asynchronous()
>>> >>> >> > # print('count %s' % sqlalchemy_connection.count)
>>> >>> >> >
>>> >>> >> > Output:
>>> >>> >> >
>>> >>> >> > Synchronous:
>>> >>> >> > Task 1 done
>>> >>> >> > test
>>> >>> >> >
>>> Engine(oracle://ADMIN:***@pydidb_high/?encoding=UTF-8&nencoding=UTF-8)
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect
>>> >>> >> > inside do_connect except block
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:39:47
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:39:49
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:39:51
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:39:54
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:39:56
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:39:59
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:01
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:04
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:09
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:15
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:17
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:19
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:21
>>> >>> >> > inside do_connect try block
>>> >>> >> > 2022-03-21 04:40:24
>>> >>> >> > 2022-03-21 04:40:26
>>> >>> >> > count 29
>>> >>> >> >
>>> >>> >> > highly appreciate any inputs.
>>> >>> >> > Regards,
>>> >>> >> > Pydi
>>> >>> >> >
>>> >>> >> > --
>>> >>> >> > SQLAlchemy -
>>> >>> >> > The Python SQL Toolkit and Object Relational Mapper
>>> >>> >> >
>>> >>> >> > http://www.sqlalchemy.org/
>>> >>> >> >
>>> >>> >> > To post example code, please provide an MCVE: Minimal,
>>> Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve
>>> for a full description.
>>> >>> >> > ---
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>>>
>>> >>> >
>>> >>> > --
>>> >>> > SQLAlchemy -
>>> >>> > The Python SQL Toolkit and Object Relational Mapper
>>> >>> >
>>> >>> > http://www.sqlalchemy.org/
>>> >>> >
>>> >>> > To post example code, please provide an MCVE: Minimal, Complete,
>>> and Verifiable Example. See http://stackoverflow.com/help/mcve for a
>>> full description.
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>>>
>>> >
>>> > --
>>> > SQLAlchemy -
>>> > The Python SQL Toolkit and Object Relational Mapper
>>> >
>>> > http://www.sqlalchemy.org/
>>> >
>>> > To post example code, please provide an MCVE: Minimal, Complete, and
>>> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
>>> description.
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>>>
>>>
>> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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