how about a stack trace?
On Oct 21, 2013, at 4:11 PM, Joseph Casale <jcas...@gmail.com> wrote:
> Hi Michael,
> I spoke with the developer of the application that launches the plugins I am
> writing and each
> python script is run by starting an entirely new process with the interpreter
> and each plugin.
>
> It should be a clean environment. From the plugins, I simply import which
> ever tables from
> the module below that I would need.
>
> In the event I am doing something wrong, my code looks like:
>
> from os import path
> from sqlalchemy import (
> Column, CheckConstraint, DDL, ForeignKey, Index, Integer, String,
> create_engine, event
> )
> from sqlalchemy.engine import Engine
> from sqlalchemy.ext.declarative import declared_attr, declarative_base
> from sqlalchemy.orm import sessionmaker
>
>
> db_name = path.join('path', 'config', 'sqlite.db')
> engine = create_engine('sqlite:///{}'.format(db_name), echo=False)
> Session = sessionmaker(bind=engine, autoflush=False, autocommit=False)
> Base = declarative_base()
>
>
> @event.listens_for(Engine, 'connect')
> def set_sqlite_pragma(dbapi_connection, connection_record):
> cursor = dbapi_connection.cursor()
> cursor.execute('PRAGMA foreign_keys=ON')
> cursor.close()
>
>
> table defs...
>
>
> if __name__ == '__main__':
> Base.metadata.create_all(engine)
>
>
> Thanks so much for the help,
> jlc
>
>
> On Sun, Oct 20, 2013 at 11:01 PM, Michael Bayer <mike...@zzzcomputing.com>
> wrote:
> the MetaData object holds one Table object per unique name given. If you
> use the Table constructor more than once with the same name and the same
> MetaData, you get this error.
>
> That's how the error is caused, then the fact that the error is "occasional"
> points strongly to a race condition of some kind, more than one thread both
> calling the constructor for Table with the same name. Patterns that could
> cause this could be some kind of unsynchronized global registry or singleton
> object that when called produces a new Table object.
>
> The recommended pattern is for Table objects (as well as mapped classes) to
> generally be declared at the module level so that these names are produced
> only at module import time, which itself should occur before the application
> starts any threads in addition to the main application thread.
>
>
>
>
> On Oct 20, 2013, at 11:04 PM, Joseph Casale <jcas...@gmail.com> wrote:
>
>> I have a module that is imported by several Python scripts run by an
>> application
>> that fires up a new interpreter session for each invocation. When not under
>> load or
>> running the code manually at the cli things work fine but once the
>> concurrency
>> raises and the application starts seeing some load it emits
>> InvalidRequestError
>> exceptions on one table.
>>
>> After searching I am not sure the results relate to my issue or maybe my lack
>> of familiarity with SQLAlchemy has the better of me.
>>
>> Any guidance would be greatly appreciated,
>> jlc
>>
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>
>
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