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[Yun Mao <yunmao@xxxxxxxxx>]

There are plenty eventlet discussion recently but I'll stick my
question to this thread, although it's pretty much a separate
question. :)

How is MySQL access handled in eventlet? Presumably it's external C
library so it's not going to be monkey patched. Does that make every
db access call a blocking call? Thanks,

Yun

On Wed, Feb 29, 2012 at 9:18 PM, Johannes Erdfelt <johannes@xxxxxxxxxxx> wrote:
> On Wed, Feb 29, 2012, Yun Mao <yunmao@xxxxxxxxx> wrote:
>> Thanks for the explanation. Let me see if I understand this.
>>
>> 1. Eventlet will never have this problem if there is only 1 OS thread
>> -- let's call it main thread.
>
> In fact, that's exactly what Python calls it :)
>
>> 2. In Nova, there is only 1 OS thread unless you use xenapi and/or the
>> virt/firewall driver.
>> 3. The python logging module uses locks. Because of the monkey patch,
>> those locks are actually eventlet or "green" locks and may trigger a
>> green thread context switch.
>>
>> Based on 1-3, does it make sense to say that in the other OS threads
>> (i.e. not main thread), if logging (plus other pure python library
>> code involving locking) is never used, and we do not run a eventlet
>> hub at all, we should never see this problem?
>
> That should be correct. I'd have to double check all of the monkey
> patching that eventlet does to make sure there aren't other cases where
> you may inadvertently use eventlet primitives across real threads.
>
> JE
>
>
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