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libdrizzle: integration with another event loop

 

I've been looking into connecting to Drizzle/MySQL via libdrizzle. My application is a (mostly) single-threaded and event driven, using libevent. I'm trying to figure out how to integrate libdrizzle with my own non-blocking event loop. There are a number of approaches I'm considering. Feedback appreciated.


My initial idea:

Spawn a "libdrizzle event thread", which will call drizzle_con_wait() in a loop. This can append events to a thread-safe queue, and wake my main event thread via a socketpair(). My main event thread will use libdrizzle to send queries and get responses.


Question 1:

* Is libdrizzle thread-safe to use in this fashion? I think the answer is "no," since the documentation states you can only use a drizzle_st from one thread.


Question 2:

* Is it possible to get the sockets being used by libdrizzle? It might be possible to add them to my own libevent loop, and call libdrizzle when there is stuff to do, rather than relying on drizzle_con_wait() to block. This would be relatively straightforward for reads, but is tricky in the case of "write blocked" events, since they need to be turned on and off on demand.


It looks like I probably need to do this the "old fashioned" way: I need to do all my libdrizzle work in a separate libdrizzle thread, and communicate with it and my main event loop.


Question 3:

* Is there a way to wake a thread blocked in drizzle_con_wait()? I will need this to implement the above technique. I'm willing to implement a "wakeup via socketpair()" API, if that seems appropriate?

Thanks for your help,

Evan Jones

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Evan Jones
http://evanjones.ca/



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