openstack team mailing list archive

[Johannes Erdfelt <johannes@xxxxxxxxxxx>]

On Tue, Mar 13, 2012, Yun Mao <yunmao@xxxxxxxxx> wrote:
> There are two places in the current master branch that use tpool:
> NWFilterFirewall and XenAPISession. Are they safe?

I've looked at XenAPISession and it appears to be safe. It doesn't use
logging nor any other locks.

It does use other Python modules, but they appear to be fine too.

I've never looked at NWFilterFirewall since I've been doing almost all
of my development on xenapi.

> I think if it's a pure C-based API call, then monkey patch should not
> mess with it and it shouldn't try to reschedule among co-routines,
> right?

If it's 100% C, then it's most likely safe. There are ways that it can
become unsafe, but it really needs to go out of it's way to do so.

> After examining, the code, I see all libvirt-based calls are blocking,
> and XenAPIs are non-blocking. This probably makes a huge difference in
> a non-trivial deployment. However, libvirt-based KVM is probably the
> most widely adopted choice right now, which is very strange..

Yeah, it's not clear to me why only that one call in libvirt is handed
off to a tpool thread. I'm not all that familiar with libvirt, nor do I
use it, so I haven't looked into that.

JE