[openstack-dev] [nova] Migration progress

Timofei Durakov tdurakov at mirantis.com
Mon Feb 8 09:28:47 UTC 2016


In case of live-migration reporting I'd rather go with real-time stats,
queried from compute, instead of reporting this data to db first. While
amount of of rpc requests/db updates is relatively small, total number of
such requests depends on amount of active migrations. While realtime data
from compute allows to decrease it. Not every migration will trigger
operator to gather statistics, and each of triggered will require only 2
rpc per request instead of 2 rpc and db write per 3/5/etc. seconds.


On Sun, Feb 7, 2016 at 10:31 PM, Jay Pipes <jaypipes at gmail.com> wrote:

> On 02/04/2016 11:02 PM, Bhandaru, Malini K wrote:
>> Another thought, for such ephemeral/changing data, such as progress,
>> why not save the information in the cache (and flush to database at a
>> lower rate), and retrieve for display to active listeners/UI from the
>> cache. Once complete or aborted, of course flush the cache.
>> Also should we provide a "verbose flag", that is only capture
>> progress information when requested? That is when a human user might
>> be issuing the command from the cli or GUI tool.
> I agree with you, Malini, on the above suggestion that there is some doubt
> as to the value of saving this temporal data to the database.
> Why not just have an on-demand model that simply routes the request for
> progress information directly to the compute node and sends the progress
> amount back directly to the nova-api service instead of going to the
> database at all?
> Another alternative would be to use a push model instead of a poll model,
> but that would require a pretty significant change to the code...
> Best,
> -jay
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