Jim Fehlig wrote:
> This patch adds a simple lock mechanism when starting domains by placing 
> a lock file in xend-domains-path/<dom_uuid>.  The lock file is removed 
> when domain is stopped.  The motivation for such a mechanism is to 
> prevent starting the same domain from multiple hosts.
> 
> If xend-domains-path is set to shared mount point, a domain will fail to 
> start on host B if it is already running on host A.  I've added an 
> option to XendOptions to control the behavior with default of no lock.
> 
> The patch certainly needs some testing (and probably adjustment) to 
> ensure the lock is handled properly on save, restore, migrate, domain 
> crash, etc. but wanted to get folks' thought on this approach before 
> continuing this endeavor.  Some simple improvements could include adding 
> info (domain name/id, start time, vmm hostname) to the lock file, 
> allowing such messages as "domain foo seems to be already running on 
> host bar" and  a --force option to create/start to override the lock.  A 
> per-domain config option could also be added to allow more fine-grained 
> control.
> 
> Comments, suggestions, alternative approaches, ... are welcome and 
> appreciated :-).
> 

this patch xen-running-lock.patch add a external lock facility to get the same
result. file-lock.c is a simple implement of the external lock utility.

the external locking facility can leverage the dlm if you are in a cluster
environment.

cheers,

zhigang

> Regards,
> Jim
> 
> 
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