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From: Eric Blake <eblake@redhat.com>
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Date: Wed, 16 May 2018 15:53:09 -0500
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Subject: Re: [Qemu-devel] [PATCH 38/42] job: Add JOB_STATUS_CHANGE QMP event
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To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org, mreitz@redhat.com, jsnow@redhat.com, armbru@redhat.com, jcody@redhat.com, qemu-devel@nongnu.org

On 05/16/2018 03:46 PM, Kevin Wolf wrote:

>>> +{ 'event': 'JOB_STATUS_CHANGE',
>>> +  'data': { 'id': 'str',
>>> +            'status': 'JobStatus' } }
>>
>> Is it worth also trying to list the old state that the transition came from?
>> But that's new compared to what block jobs are currently doing, so if we
>> can't come up with a strong reason to add that, I'm okay.
> 
> If a management tool needs this information (I don't see why), it just
> needs to keep track of the last state it had seen, no?

And if you miss an event, the previous state is not preserved for any 
later query-job command.  Exposing something in a (possibly-missed) 
event that is not available elsewhere doesn't buy us much.  So I agree - 
there is no strong reason to advertise the previous state.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org