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Add another up-call to the cells v2 caveats list 

Due to change I8d426f2635232ffc4b510548a905794ca88d7f99 in Pike,
which ironically was meant to avoid up-calls (I think), it
introduced an up-call during reschedules for server create and
resize to set the instance.availability_zone based on the
alternate host selected during the reschedule.

This adds the up-call to our list of known issues in the cells
v2 docs so we can track the issue and make people aware of it.

Change-Id: Id819f91477613a013b89b1fb0b2def3b0fd4b08c
Related-Bug: #1781286
This commit is contained in:
Matt Riedemann 2018-07-11 19:21:44 -04:00
parent 39b05ee9e3
commit 1160ae7a65
1 changed files with 10 additions and 1 deletions
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11
doc/source/user/cellsv2-layout.rst
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@ -320,7 +320,7 @@ implement some features without such connectivity. Thus, anything that
requires a so-called "upcall" will not function. This impacts the requires a so-called "upcall" will not function. This impacts the
following: following:
#. Instance reschedules during boot and resize #. Instance reschedules during boot and resize (part 1)
.. note:: This has been resolved in the Queens release [#]_. .. note:: This has been resolved in the Queens release [#]_.
@ -331,6 +331,7 @@ following:
.. note:: This has been resolved in the Rocky release [#]_. .. note:: This has been resolved in the Rocky release [#]_.
#. Attaching a volume and ``[cinder]/cross_az_attach=False`` #. Attaching a volume and ``[cinder]/cross_az_attach=False``
#. Instance reschedules during boot and resize (part 2)
The first is simple: if you boot an instance, it gets scheduled to a The first is simple: if you boot an instance, it gets scheduled to a
compute node, fails, it would normally be re-scheduled to another compute node, fails, it would normally be re-scheduled to another
@ -369,6 +370,14 @@ volume and must tell Cinder in which availability zone to create the volume.
Long-term, volume creation during boot from volume should be moved to the Long-term, volume creation during boot from volume should be moved to the
top-level superconductor which would eliminate this AZ up-call check problem. top-level superconductor which would eliminate this AZ up-call check problem.
The sixth is detailed in `bug 1781286`_ and similar to the first issue.
The issue is that servers created without a specific availability zone
will have their AZ calculated during a reschedule based on the alternate host
selected. Determining the AZ for the alternate host requires an "up call" to
the API DB.
.. _bug 1781286: https://bugs.launchpad.net/nova/+bug/1781286
.. [#] https://blueprints.launchpad.net/nova/+spec/efficient-multi-cell-instance-list-and-sort .. [#] https://blueprints.launchpad.net/nova/+spec/efficient-multi-cell-instance-list-and-sort
.. [#] https://specs.openstack.org/openstack/nova-specs/specs/queens/approved/return-alternate-hosts.html .. [#] https://specs.openstack.org/openstack/nova-specs/specs/queens/approved/return-alternate-hosts.html
.. [#] https://blueprints.launchpad.net/nova/+spec/live-migration-in-xapi-pool .. [#] https://blueprints.launchpad.net/nova/+spec/live-migration-in-xapi-pool