[Xen-devel] Re: Live Migration problems using xenapi with xm

[Ben Guthro <bguthro@xxxxxxxxxxxxxxx>]

I've managed to track this down to being a bug in HVM migration using 
XenAPI.
It seems that restore is trying to restore a PV guest, while save is 
trying to save an HVM guest... so the protocol of how many mytes to read 
on the socket is off, and naturally fails when it tries to read much 
more data than the max batch size allows.
Tracing this back, it seems to come down to the "is_hvm" method of the 
XendConfig class, which checks the "HVM_boot_policy" parameter. For some 
reason, it seems this parameter is not being preserved during domain 
creation with xenapi, because by the time migration occurs, the 
dictionary item no longer exists.
I'll continue to dig further, but if anyone has any thoughts on this, 
I'd welcome pointers.

Ben Guthro wrote:
> I am seeing a problem when live migrating a guest under unstable when 
> I have xm configured to XenAPI.
> If my xm-config.xml file has the XenAPI stuff commented out - live 
> migrate (xm migrate --live <domid> <dest IP>) seems to be working in 
> my test environment.
> However, if I enable it - I get failures when migrating the same guest 
> (see dump from xend.log below.)  They obviously go down quite 
> different code paths in these two cases.
> Being somewhat new to the xm, and xenapi control stacks - I was hoping 
> someone might point me in the right direction to track down what might 
> be happening here...
> Any help is appreciated.
>
> Ben
>
> Xend log snippet:
>
> 2007-11-07 09:01:35 15422] DEBUG (XendCheckpoint:88) [xc_save]: 
> /usr/lib64/xen/bin/xc_save 20 2 0 0 5
> [2007-11-07 09:01:35 15422] INFO (XendCheckpoint:362) Saving memory 
> pages: iter 1   0%ERROR Internal error: Error when writing to state 
> file (5) (errno 104)
> [2007-11-07 09:01:35 15422] INFO (XendCheckpoint:362) Save exit rc=1
> [2007-11-07 09:01:36 15422] ERROR (XendCheckpoint:140) Save failed on 
> domain VS022 (2).
> Traceback (most recent call last):
> File "/usr/lib64/python/xen/xend/XendCheckpoint.py", line 108, in save
>   forkHelper(cmd, fd, saveInputHandler, False)
> File "/usr/lib64/python/xen/xend/XendCheckpoint.py", line 350, in 
> forkHelper
>   raise XendError("%s failed" % string.join(cmd))
> XendError: /usr/lib64/xen/bin/xc_save 20 2 0 0 5 failed
> [2007-11-07 09:01:36 15422] DEBUG (XendDomainInfo:1856) 
> XendDomainInfo.resumeDomain(2)
> [2007-11-07 09:01:36 15422] ERROR (xmlrpclib2:166) Internal error 
> handling VM.migrate
> Traceback (most recent call last):
> File "/usr/lib64/python/xen/util/xmlrpclib2.py", line 131, in 
> _marshaled_dispatch
>   response = self._dispatch(method, params)
> File "/usr/lib64/python2.4/SimpleXMLRPCServer.py", line 406, in _dispatch
>   return func(*params)
> File "/usr/lib64/python/xen/xend/XendAPI.py", line 221, in f
>   return func(self, *args, **kwargs)
> File "/usr/lib64/python/xen/xend/XendAPI.py", line 256, in check_session
>   return func(self, session, *args, **kwargs)
> File "/usr/lib64/python/xen/xend/XendAPI.py", line 312, in <lambda>
>   'VM', func, *args, **kwargs)
> File "/usr/lib64/python/xen/xend/XendAPI.py", line 268, in _check_ref
>   return func(api, session, ref, *args, **kwargs)
> File "/usr/lib64/python/xen/xend/XendAPI.py", line 1763, in VM_migrate
>   bool(live), resource, port)
> File "/usr/lib64/python/xen/xend/XendDomain.py", line 1282, in 
> domain_migrate
>   XendCheckpoint.save(sock.fileno(), dominfo, True, live, dst)
> File "/usr/lib64/python/xen/xend/XendCheckpoint.py", line 142, in save
>   dominfo.resumeDomain()
> File "/usr/lib64/python/xen/xend/XendDomainInfo.py", line 1885, in 
> resumeDomain
>   if self.is_hvm():
> File "/usr/lib64/python/xen/xend/XendDomainInfo.py", line 2139, in 
> __getattr__
>   raise AttributeError()
> AttributeError
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