nova/releasenotes/notes/pike-multicell-api-ae4fbebd711165ce.yaml
Matt Riedemann 9a5c3cd7da Add release note and update cell install guide for multi-cell limitations
As of change If1e03c9343b8cc9c34bd51c2b4d25acdb21131ff, using
"nova hypervisor-list" before compute hosts are mapped to a cell
will result in an empty list.

Our cells v2 install steps mention using 'nova hypervisor-list' after
creating a cell and starting compute services to tell when to run
the discover_hosts command, but now hypervisor-list won't work until
you've run discover_hosts, so it's a catch-22.

This change adds a release note to let people writing deployment tools
to know about the change in behavior and also updates the install steps
to use service-list instead of hypervisor-list, since service-list does
not require the compute host to be mapped to the cell first.

We are going to need to make a similar change in the OpenStack install
guide since that also mentions using 'nova hypervisor-list' before
discover_hosts.

Change-Id: If2baab40c2e2a3de20e561bba50688d615b002ef
Closes-Bug: #1682060
2017-04-21 10:11:03 -07:00

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YAML

---
upgrade:
- |
Parts of the compute REST API are now relying on getting information from
cells via their mappings in the ``nova_api`` database. This is to support
multiple cells. For example, when listing compute hosts or services, all
cells will be iterated in the API and the results will be returned.
This change can have impacts, however, to deployment tooling that relies on
parts of the API, like listing compute hosts, `before` the compute hosts
are mapped using the ``nova-manage cell_v2 discover_hosts`` command.
If you were using ``nova hypervisor-list`` after starting new nova-compute
services to tell when to run ``nova-manage cell_v2 discover_hosts``, you
should change your tooling to instead use one of the following commands::
nova service-list --binary nova-compute [--host <hostname>]
openstack compute service list --service nova-compute [--host <host>]
As a reminder, there is also the
``[scheduler]/discover_hosts_in_cells_interval`` configuration option which
can be used to automatically discover hosts from the nova-scheduler
service.