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Simon Bierbaum
bierbaum at vierfalt.com
Fri Aug 22 04:12:38 EDT 2008
I solved the problem in the meantime. There was an SQLAlchemy session object I did not clean up with close() properly after finishing up a request. It still lived in the second request, resulting in correct data being fetched from the database, but an out-of-date object still present in the session was returned. Thanks again for your help :-) Simon Am 22.08.2008 um 02:28 schrieb Graham Dumpleton: > 2008/8/21 Simon Bierbaum <bierbaum at vierfalt.com>: >> Thanks, Graham. From reading this and also >> http://www.dscpl.com.au/wiki/ModPython/Articles/ >> ModuleImportingIsBroken, I >> believe that two distinct requests, handled consecutively by the same >> unrecycled apache prefork child, will see the same global module >> objects and >> thus the same module state. Is that correct? > > Yes. > >> I know this data sharing method >> should not be used, > > The sharing method can be used, but not for stuff that must be the > same across all processes. Thus you can still use module global data > for caching information which is effectively read only and where if > necessary you have checks to ensure it is refreshed as needed. > >> but it would mean the bug I'm hunting could be caused by >> some unintentionally left over state within a module, making the >> second >> request work with stale data. > > It could also be due to that caching mechanism not being threaded > protected properly. For example, if one request is updating the cache > will a concurrent request in same process is using data from the > cache. > > Without know more detail about the problem you are seeing and example > code showing how you are using global module data, had to say. > > Graham > >> Am 20.08.2008 um 22:43 schrieb Graham Dumpleton: >> >>> For a start, read: >>> >>> >>> http://www.dscpl.com.au/wiki/ModPython/Articles/ >>> TheProcessInterpreterModel >>> >>> Graham >>> >>> 2008/8/21 Simon Bierbaum <bierbaum at vierfalt.com>: >>>> >>>> Hi all, >>>> >>>> I would like to know exactly what bits in mod_python are persistent >>>> across >>>> multiple requests to the same apache process. I.e., once apache is >>>> started >>>> and mod_python is loaded, between two requests served by the >>>> same apache >>>> process and the same Python handler, >>>> >>>> - does mod_python reload modules, i.e. is module initialization >>>> code only >>>> run once during the apache process lifespan? >>>> - is there a way for modules to store objects persistently, e.g. a >>>> database >>>> connection pool? >>>> - what happens to variables defined in the handler script but >>>> not locally >>>> within the handler() function (I'm not sure whether this is what >>>> Python >>>> calls "global")? >>>> >>>> I have a bug in my application which uses mod_python, MySQLdb >>>> and the >>>> InnoDB >>>> storage engine revolving around transactions, and it's driving me >>>> mad...any >>>> help or a pointer to documentation is greatly appreciated. >>>> >>>> Thanks, Simon >>>> _______________________________________________ >>>> Mod_python mailing list >>>> Mod_python at modpython.org >>>> http://mailman.modpython.org/mailman/listinfo/mod_python >>>> >> >> _______________________________________________ >> Mod_python mailing list >> Mod_python at modpython.org >> http://mailman.modpython.org/mailman/listinfo/mod_python >>
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