Re: [Qemu-devel] [RFC v4 19/21] blockjobs: Expose manual property

[John Snow]

On 02/27/2018 03:16 PM, Eric Blake wrote:
> On 02/23/2018 05:51 PM, John Snow wrote:
>> Expose the "manual" property via QAPI for the backup-related jobs.
>> As of this commit, this allows the management API to request the
>> "concluded" and "dismiss" semantics for backup jobs.
>>
>> Signed-off-by: John Snow <address@hidden>
>> ---
>>   blockdev.c           | 19 ++++++++++++++++---
>>   qapi/block-core.json | 32 ++++++++++++++++++++++++++------
>>   2 files changed, 42 insertions(+), 9 deletions(-)
>>
> 
>> +++ b/qapi/block-core.json
>> @@ -1177,6 +1177,16 @@
>>   # @job-id: identifier for the newly-created block job. If
>>   #          omitted, the device name will be used. (Since 2.7)
>>   #
>> +# @manual: True to use an expanded, more explicit job control flow.
>> +#          Jobs may transition from a running state to a pending state,
>> +#          where they must be instructed to complete manually via
>> +#          block-job-finalize.
>> +#          Jobs belonging to a transaction must either all or all not
>> use this
>> +#          setting. Once a transaction reaches a pending state,
>> issuing the
>> +#          finalize command to any one job in the transaction is
>> sufficient
>> +#          to finalize the entire transaction.
> 
> The previous commit message talked about mixed-manual transactions, but
> this seems to imply it is not possible.  I'm fine if we don't support
> mixed-manual transactions, but wonder if it means any changes to the
> series.
> 
> Otherwise looks reasonable from the UI point of view.
> 

More seriously, this documentation I wrote doesn't address the totality
of the expanded flow. I omitted dismiss here by accident as well. This
is at best a partial definition of the 'manual' property.

I'd like to use _this_ patch to ask the question: "What should the
proper noun for the QEMU 2.12+ Expanded Block Job Management Flow
Mechanism be?"

I'm not too sure, but "Manual mode" leaves a lot to be desired.

I keep calling it something like "2.12+ Job Management" but that's not
really descriptive. I conceptualize the feature as the addition of a
purposefully more "needy" and less automatic completion mechanism, hence
the "manual"

Anyway, I'd like to figure out a good "documentation name" for it so I
can point all instances of the creation property (for drive-backup,
drive-mirror, and everyone else) to a central location that explains the
STM and what exactly the differences between manual=on/off are. I'd then
like to expose this property via query and link the documentation there
to this description, too.

It'd be nice-- under the same arguments that prompted 'dismiss'-- to say
that if a client crashes it can reconnect and discover what kind of
attention certain jobs will need by asking for the manual property back.

--js