On Wed, Feb 03, 2016 at 10:37:24AM +0000, Koniszewski, Pawel wrote: > Hello everyone, > > On the yesterday's live migration meeting we had concerns that interval of > writing migration progress to the database is too short. > > Information about migration progress will be stored in the database and > exposed through the API (/servers/<uuid>/migrations/<id>). In current > proposition [1] migration progress will be updated every 2 seconds. It > basically means that every 2 seconds a call through RPC will go from compute > to conductor to write migration data to the database. In case of parallel > live migrations each migration will report progress by itself. > > Isn't 2 seconds interval too short for updates if the information is exposed > through the API and it requires RPC and DB call to actually save it in the > DB? > > Our default configuration allows only for 1 concurrent live migration [2], > but it might vary between different deployments and use cases as it is > configurable. Someone might want to trigger 10 (or even more) parallel live > migrations and each might take even a day to finish in case of block > migration. Also if deployment is big enough rabbitmq might be fully-loaded. > I'm not sure whether updating each migration every 2 seconds makes sense in > this case. On the other hand it might be hard to observe fast enough that > migration is stuck if we increase this interval...
Do we have any actual data that this is a real problem. I have a pretty hard time believing that a database update of a single field every 2 seconds is going to be what pushes Nova over the edge into a performance collapse, even if there are 20 migrations running in parallel, when you compare it to the amount of DB queries & updates done across other areas of the code for pretty much every singke API call and background job. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
