Mysql2
From the makers of InspIRCd.
/* THE NONBLOCKING MYSQL API! * * MySQL provides no nonblocking (asyncronous) API of its own, and its developers recommend * that instead, you should thread your program. This is what i've done here to allow for * asyncronous SQL requests via mysql. The way this works is as follows: * * The module spawns a thread via pthreads, and performs its mysql queries in this thread, * using a queue with priorities. There is a mutex on either end which prevents two threads * adjusting the queue at the same time, and crashing the ircd. Every 50 milliseconds, the * worker thread wakes up, and checks if there is a request at the head of its queue. * If there is, it processes this request, blocking the worker thread but leaving the ircd * thread to go about its business as usual. During this period, the ircd thread is able * to insert futher pending requests into the queue. * * Once the processing of a request is complete, it is removed from the incoming queue to * an outgoing queue, and initialized as a 'response'. The worker thread then signals the * ircd thread (via a loopback socket) of the fact a result is available, by sending the * connection ID through the connection. * * The ircd thread then mutexes the queue once more, reads the outbound response off the head * of the queue, and sends it on its way to the original calling module. * * XXX: You might be asking "why doesnt he just send the response from within the worker thread?" * The answer to this is simple. The majority of InspIRCd, and in fact most ircd's are not * threadsafe. This module is designed to be threadsafe and is careful with its use of threads, * however, if we were to call a module's OnRequest even from within a thread which was not the * one the module was originally instantiated upon, there is a chance of all hell breaking loose * if a module is ever put in a re-enterant state (stack corruption could occur, crashes, data * corruption, and worse, so DONT think about it until the day comes when InspIRCd is 100% * gauranteed threadsafe!) * * For a diagram of this system please see http://www.inspircd.org/wiki/Mysql2 */
