Le 12/04/2019 à 15:58, Mike Bayer a écrit :
it's likely that a database connection is being returned to the pool
in an invalid state.
Switching to NullPool temporarily might reveal that this solves all
the issues ; at the very least, I would try setting pool_recycle to a
low number, like 5 minutes, however this won't prevent the problem,
just make it less likely. What you do need to find are stack traces
that precede the error, to give a clue why a connection would be
placed in the pool in a bad state.
The other possibility is that your application is actually sharing a
single connection across threads in some way which would be a
different problem though with a lot of similar behaviors. Are there
any global in-memory caches being used of objects where an ORM object
might be shared out among threads, or a background worker thread of
some kind, anything like that ? Does the application use a
"scoped_session" pattern and maybe the session being passed around in
some cases isn't actually scoped?
On Fri, Apr 12, 2019 at 4:03 AM tonthon <tontho...@gmail.com> wrote:
Le 10/04/2019 à 17:12, Mike Bayer a écrit :
On Wed, Apr 10, 2019 at 9:23 AM tonthon <tontho...@gmail.com> wrote:
Hi,
We're using sqlalchemy in a Pyramid Web Application.
We use the ZopeTransactionExtension and our session factory is initialized this
way :
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
We use the pyramid_tm that wraps each web requests in a transaction.
Our services are served through apache and mod_wsgi (1 process, 10 threads).
We recently faced the following error :
193.253.40.35 - 2019-04-08 09:29:23,054 ERROR Exception during reset or similar
([sqlalchemy.pool.QueuePool._finalize_fairy:721])
Traceback (most recent call last):
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line
712, in _finalize_fairy
fairy._reset(pool)
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/pool.py", line
881, in _reset
self._reset_agent.rollback()
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py",
line 1632, in rollback
self._do_rollback()
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py",
line 1670, in _do_rollback
self.connection._rollback_impl()
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py",
line 706, in _rollback_impl
self._handle_dbapi_exception(e, None, None, None, None)
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py",
line 1413, in _handle_dbapi_exception
exc_info
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/util/compat.py",
line 265, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py",
line 704, in _rollback_impl
self.engine.dialect.do_rollback(self.connection)
File
"/var/www/autonomie/local/lib/python2.7/site-packages/sqlalchemy/dialects/mysql/base.py",
line 1804, in do_rollback
dbapi_connection.rollback()
ProgrammingError: (_mysql_exceptions.ProgrammingError) (2014, "Commands out of sync;
you can't run this command now") (Background on this error at:
http://sqlalche.me/e/f405)
I can't reproduce this problem that seems to happen randomly.
Could anyone help me giving some points to investigate ?
Is there some tuning to do (I already set the pool_recycle var) ?
the most important thing is what driver are you using and what version?
are you doing anything with SAVEPOINTs or greenlets / eventlet ?
is the web application experiencing timeouts of some kind, such that
transactions are being dropped ?
is the above error only showing up in logs or is it occurring
synchronously with a web request and causing the request to fail ?
We use mysqlclient 1.4.1.
We don't use any greenlet or eventlet nor savepoints.
I havn't seen any timeout happening so far.
The given error is happening during the request's lifecycle resulting in a HTTP
500 error code
After the error, the user refreshes and it works.
I don't know if it could be related, but we also see things like "NoSuchColumnError:
"Could not locate column in row for column 'count(*)'".
Thanks in advance
Best regards
Gaston
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http://www.sqlalchemy.org/
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