inboundfilter at gmail.com
Wed Jan 16 15:14:11 EST 2008
The topic has been covered many times before, but I'm hoping someone can clarify what to expect when using the technique described in this thread: http://www.modpython.org/pipermail/mod_python/2005-October/019287.html Specifically: > Thus, it is preferable that resource allocation and the storage of the > handle be done in a Python module that is not imported using the module > loading system of mod_python but that "import" be used instead. Such a > module should preferably not be in the document tree but elsewhere on > the Python path. As described in the link above, use an access function > in that module which returns, and creates as necessary, the resource > handle. That's basically what I'm doing, under Apache 2.2 with mpm_worker, mod_python 3.3, Publisher handler, postgres, psycopg2. In my implementation, the module has one top-level name for a psycopg2.PersistentConnectionPool object, an init_pool() function to set that object, a get_connection() function which returns a reference to it, and a release(conn) function to return the connection to the pool. Additionally, get_connection() will call init_pool() if the pool object is None. The applications use only the get_connection() and release(conn) functions. As far as I can tell, this is working fine. What I'm unsure of: 1) How many pools could I potentially end up with? One pool per httpd process, or per interpreter? 2) Are those pools and their connections available to all the threads in a given process? 3) Will imports in the applications overwrite the pool object initialized by prior calls to init_pool() or get_connection()? Related to #2? Does module caching deal with this? 4) Will the pool(s)/connections be closed when Apache kills off a process? Automatically? Will I need a specific cleanup function? How/when would that be called()? I've also read this whole thread: http://www.modpython.org/pipermail/mod_python/2005-September/019092.html, and this article: http://www.dscpl.com.au/articles/modpython-004.html, both of which were helpful with how to deal with the connections, but don't really talk about what I'm asking here.