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Re: [Xen-devel] problem restarting xenstored

On Thu, Dec 07, 2006 at 03:21:59PM +0000, Jan Beulich wrote:

> As any other daemon, I'd assume it should be possible to restart xenstored 
> (i.e.
> if it crashed or if, during development, a fix was made to it that needs to be
> tested). However, as I learned after over a day of digging, things don't work
> anymore after doing so: Since the watches are transient, they're lost with the
> daemon going away.
> Right now I specifically need this in already mentioned scenarios where I want
> to not touch the base installation of a system or need parallel versions 
> installed,
> but as described above I see the general issue broader (e.g. it obviously
> doesn't make sense to try to start xenstored from 'xend restart' because of
> described problems).

xend restart doesn't restart xenstored, for this very reason of course.

I don't see why this is a problem for your "multiple installed versions of
Xen" -- surely you reboot in order to switch toolstacks?

Keir did have some ideas about making xenstored restartable -- reregistering
the watches when the daemon restarts -- but no-one's got around to doing that
work.  Are you volunteering?  ;-)

> For some reason, this wasn't a big problem when the base installation was
> 3.0.2-based - apparently something else prevented xenbus' event channel
> handler to get triggered when the 3.0.2 xenstored loaded, and hence all the
> needed watches got installed only when the proper version was loaded the
> first time, giving the impression that things work as expected (until perhaps
> reloading it a second time).

You've lost me -- what are you trying to do?  Are you trying to start multiple
versions of xenstored during the same boot?

Xenstored actually hasn't changed in any manner that would make it
backwards-incompatible, AFAIK, so you ought to be able to run a 3.0.2
toolstack with xenstored from 3.0.4, for example.


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