Proposal: connection pooling

Here comes my first idea of how to implement database pooling in multithreaded PHP4 versions. I was inspired by the connection pooling in AOLServer (see nsd/dbinit.c). There are still some open issues: -Can pools be implemented as an extension module? The global startup/shutdown functions PHP_GINIT() and PHP_GSHUTDOWN() could provide a hook to allocate / free the needed data structures available to all threads. -AOLServer pools synchronize thread access to pools via condition variables, this is not available in TSRM, see Ns_Cond type below. -AOLServer provides a timeout mechanism for closing unneeded connections. This is done via Ns_ScheduleProc(), an equivalent isn't available with other servers. int RegisterPool(max_entries, void (*pool_entry_ctor)(void *), void (*pool_entry_dtor)(void *)); int GetPoolEntry(int pool, *pdata, int wait); void ReleasePoolEntry(int pool, *pdata); void pool_entry_ctor(void *ptr); void pool_entry_dtor(void *ptr); To use pools: -Provide constructor function to allocate connection struct and connect to DB -Provide destructor function to disconnect from DB and free connection struct -Register the pool on module startup, this returns a pool id -Register a list destructor for pooled connections that will call ReleasePoolEntry() on request shutdown or explicit connection closing. -Call GetPoolEntry() to retrieve a database handle. Register a resource with ZEND_REGISTER_RESOURCE() and the type you got via register_list_destructor above Data structures for Pools: typedef struct _pool_entry { void *pdata; struct pool_entry *next_entry; struct pool *pool_ptr; } pool_entry typedef struct _pool { int id; int max_entries; struct pool_entry *first_entry; struct pool_entry *last_entry; Ns_Tls lock; Ns_Cond waitCond; Ns_Cond getCond; void (*pool_entry_ctor)(void *); void (*pool_entry_dtor)(void *); } pool; struct _pools{ struct pool *this_pool; struct pool *next_pool; } pools; Your comments are welcome, -Andreas