[openstack-dev] Nova no-db-compute update

Russell Bryant rbryant at redhat.com
Tue Oct 23 15:27:31 UTC 2012


Greetings,

The "no-db-compute" project is for removing direct database access from
the nova-compute service.  The purpose of this message is to provide an
update on the status of the effort.

You can find the blueprint here, but it doesn't contain details:

    https://blueprints.launchpad.net/nova/+spec/no-db-compute

There was a session on this topic at the Grizzly design summit.  You can
find the notes from that session in this etherpad:

    https://etherpad.openstack.org/grizzly-nova-no-db-compute

A good amount of progress was made towards this goal in Folsom and we
are intending to complete the project for Grizzly.  The work is
primarily being done by myself and Dan Smith, but other contributions
are certainly welcome.

This week we started doing an audit of the remaining database access
that we need to address.  The notes are on the etherpad.  Our short term
plan is to complete this audit and then continue to remove the database
accesses that follow the pattern of all of the other "no-db-messaging"
changes.  That means we can just send more data in the rpc message from
the api service to avoid database reads in nova-compute.

Once we are down to the changes that require something more significant,
which will primarily be writes to the database, we can discuss detailed
proposals in the context of the specific operations.  We discussed two
possible approaches in the summit session that both involve adding a new
service.  One approach is a simple db writer service (nova-sink).  The
other approach would be to start breaking up nova-compute into a
nova-compute orchestration service that doesn't run on the hypervisor
nodes and a more stripped down service that runs on the hypervisor
nodes.  We can revisit the details once we have cut down the remaining
problems to what must be solved by this new design.

Thanks,

-- 
Russell Bryant



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