Re: [Qemu-devel] Re: [PATCH 1/5] Exit if incoming migration fails

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/25/2010 01:37 PM, Juan Quintela wrote:
> Luiz Capitulino<lcapitulino@redhat.com>  wrote:
>    
>> On Tue, 25 May 2010 16:21:01 +0200
>> Juan Quintela<quintela@redhat.com>  wrote:
>>
>>      
>>> Signed-off-by: Juan Quintela<quintela@redhat.com>
>>> ---
>>>   migration.c |   16 ++++++++++------
>>>   migration.h |    2 +-
>>>   vl.c        |    7 ++++++-
>>>   3 files changed, 17 insertions(+), 8 deletions(-)
>>>
>>>        
>    
>>   While I agree on the change, I have two comments:
>>
>> 1. By taking a look at the code I have the impression that most of the
>>     fun failures will happen on the handler passed to qemu_set_fd_handler2(),
>>     do you agree? Any plan to address that?
>>      
> That is outgoing migration, not incoming migration.
> Incoming migration in synchronous..
>
>
>    
>> 1. Is exit()ing the best thing to be done? I understand it's the easiest
>>     and maybe better than nothing, but wouldn't it be better to enter in
>>     paused-forever state so that clients can query and decide what to do?
>>      
> For incoming migration, if it fails in the middle, every bet is off.
> You are in a really inconsistent state, not sure which one, and if
> migration was live, with the other host possibly retaking the disks to
> continue.
>    

I agree that exiting is the only sane behavior for the destination.

Regards,

Anthony Liguori

> In some cases, you can't do anything:
> - you got passed an fd, and fd got closed/image corrupted/...
> - you got passed an exec command like "exec: gzip -d<  foo.gz"
>    If gzip failed once, it will fail forever.
>
> If you are running it by hand, cursor up + enter, and you are back
> If you are using a management application, it is going to be easier to
> restart the process that trying to cleanup everything.
>
> Experience shows that people really tries to do weird things when
> machine is in this state.
>
> Later, Juan.
>
>