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Upgrade note for concurrency mode default change

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This is a follow up for the release notes added in the commit
35207ee8b5 that changed the default mode
for the scheduler and the API services. At that time we missed to note
the upgrade impact of such change. So this patch extends the reno with
an upgrade note.

Change-Id: I280e7eb9c1da6eeaf50e96e8b19e296961f2651a
Signed-off-by: Balazs Gibizer <gibi@redhat.com>
This commit is contained in:
Balazs Gibizer
2025-12-05 11:30:46 +01:00
parent 1712ae48e3
commit f73a23b4d4
2 changed files with 31 additions and 3 deletions
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doc/source/admin/concurrency.rst
+16 -1
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@@ -24,7 +24,7 @@ Selecting concurrency mode for a service
Since nova 33.0.0 (2026.1 Gazpacho) the nova-scheduler, nova-api, and
nova-metadata are using native threading by default. The rest of the
services are using eventlet by default in this release. The concurrency mode
can be configured via setting the environment variable
can be configured per service via setting the environment variable
``OS_NOVA_DISABLE_EVENTLET_PATCHING``. Setting that variable to ``true``
requests the native threading mode while setting it to ``false`` requests the
eventlet mode. If the variable is not set the above default is applied.
@@ -37,6 +37,10 @@ eventlet mode. If the variable is not set the above default is applied.
Since nova 33.0.0 (2026.1 Gazpacho) also the nova-conductor can be switched
to native threading mode.
Since nova 33.0.0 (2026.1. Gazpacho) the nova-scheduler, nova-metadata, and
nova-api using native threading mode by default but still can be switched
back to eventlet if needed.
Tunables for the native threading mode
--------------------------------------
@@ -114,3 +118,14 @@ adding the `read_timeout`__ connection parameter to the connection string.
We recommend using both in deployments where Nova services are running in
native threading mode.
Upgrading to nova 33.0.0 (2026.1. Gazpacho) or newer
----------------------------------------------------
In nova 33.0.0 (2026.1. Gazpacho) the default concurrency mode of
nova-scheduler, nova-api, and nova-metadata service are switched to native
threading. We recommend to decouple the upgrade from the concurrency mode
change to reduce the risk of issues. To do that either test and tune the native
threading mode of these services already in 2025.2 (Flamingo) or ensure that
your service configuration is explicitly using the eventlet mode before you
upgrade and only change to threading mode after the upgrade was successful.