openstack/nova
Code Issues Proposed changes

Add release note and update cell install guide for multi-cell limitations

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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
This commit is contained in:
Matt Riedemann
2017-04-14 11:21:17 -04:00
committed by Dan Smith
parent ae637e70a7
commit 9a5c3cd7da
3 changed files with 27 additions and 2 deletions
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3
doc/source/cells.rst
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@@ -386,7 +386,8 @@ database yet. This will set up a single cell Nova deployment.
configuration file if not specified on the command line.
6. Configure and start your compute hosts. Before step 7, make sure you have
compute hosts in the database by running ``nova hypervisor-list``.
compute hosts in the database by running
``nova service-list --binary nova-compute``.
7. Run the ``discover_hosts`` command to map compute hosts to the single cell::

2
doc/source/man/nova-manage.rst
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@@ -148,7 +148,7 @@ Nova Cells v2
any hosts which are not currently mapped. If a host is already mapped
nothing will be done. You need to re-run this command each time you add
more compute hosts to a cell (otherwise the scheduler will never place
instances there).
instances there and the API will not list the new hosts).
``nova-manage cell_v2 list_cells [--verbose]``

24
releasenotes/notes/pike-multicell-api-ae4fbebd711165ce.yaml Normal file
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@@ -0,0 +1,24 @@
---
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.