From 9873303dc2509cbe28fa6803a8de3585c937f8b9 Mon Sep 17 00:00:00 2001
From: Rodolfo Alonso Hernandez <ralonsoh@redhat.com>
Date: Wed, 11 Jun 2025 06:05:34 +0000
Subject: [PATCH] Add deprecation warning for the OVN Metadata agent

The OVN Metadata agent is deprecated in favor of the OVN Agent with
metadata extension.

Related-Bug: #2112313
Change-Id: Ibdde91c963b1f75b0f177dae5690d50f30160018
Signed-off-by: Rodolfo Alonso Hernandez <ralonsoh@redhat.com>
---
 doc/source/ovn/ovn_agent.rst                   | 18 ++++++++++++++++++
 neutron/agent/ovn/metadata/agent.py            |  4 ++++
 ...ata-agent-deprecation-33d5e5acba902391.yaml | 15 +++++++++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 releasenotes/notes/ovn-metadata-agent-deprecation-33d5e5acba902391.yaml

diff --git a/doc/source/ovn/ovn_agent.rst b/doc/source/ovn/ovn_agent.rst
index 9a3e28c117e..4e9f592f3ab 100644
--- a/doc/source/ovn/ovn_agent.rst
+++ b/doc/source/ovn/ovn_agent.rst
@@ -42,6 +42,9 @@ agent configuration file in the "extensions" parameter:
     extensions = metadata
 
 
+In ``devstack``, the ``[agent]extensions`` configuration parameter is set by
+``OVN_AGENT_EXTENSIONS``.
+
 Each extension will inherit from ``OVNAgentExtension``, which provides the API
 for an OVN agent extension. The extensions are loaded in two steps:
 
@@ -73,3 +76,18 @@ for new events that will trigger actions. As mentioned in the previous section,
 each extension will subscribe to a set of events from the OVN and OVS
 databases; these events will trigger a set of actions executed on the OVN
 agent.
+
+
+Zuul CI testing
+---------------
+
+In order to enable this new agent, it is needed:
+
+* To disable the default OVN Metadata agent (devstack service
+  ``q-ovn-metadata-agent``).
+* To enable the OVN agent (devstack service ``q-ovn-agent``).
+
+Check the Neutron CI job ``neutron-tempest-plugin-ovn`` definition and
+`[OVN] Use the OVN agent in "neutron-tempest-plugin-ovn"
+<https://review.opendev.org/c/openstack/neutron-tempest-plugin/+/909860>`_
+for more information.
diff --git a/neutron/agent/ovn/metadata/agent.py b/neutron/agent/ovn/metadata/agent.py
index df58581d8d3..484d9d1ff90 100644
--- a/neutron/agent/ovn/metadata/agent.py
+++ b/neutron/agent/ovn/metadata/agent.py
@@ -492,6 +492,10 @@ class MetadataAgent:
         self._update_chassis_private_config()
         self._update_metadata_sb_cfg_key()
 
+        LOG.warning(
+            'The OVN Metadata agent is deprecated in favor of the OVN agent '
+            'with the metadata extension. It has been deprecated in 2025.2 '
+            'and will be removed in 2026.2')
         self._proxy.wait()
 
     @ovn_utils.retry()
diff --git a/releasenotes/notes/ovn-metadata-agent-deprecation-33d5e5acba902391.yaml b/releasenotes/notes/ovn-metadata-agent-deprecation-33d5e5acba902391.yaml
new file mode 100644
index 00000000000..be0e8e0b17f
--- /dev/null
+++ b/releasenotes/notes/ovn-metadata-agent-deprecation-33d5e5acba902391.yaml
@@ -0,0 +1,15 @@
+---
+deprecations:
+  - |
+    The OVN Metadata agent is deprecated in favor of the `OVN agent
+    <https://docs.openstack.org/neutron/latest/ovn/ovn_agent.html>`_. In order
+    to replace the the first with the second one, it is only needed to stop
+    the OVN Metadata agent and start the OVN agent with the "metadata"
+    plugable extension enabled. The OVN agent allows plugable extensions, like
+    for example "metadata", that can be enabled or disabled `via the
+    configuration file
+    <https://docs.openstack.org/neutron/latest/ovn/ovn_agent.html#plugable-extensions>`_.
+    Apart from the ``[DEFAULT]extensions`` configuration parameter required
+    in the OVN agent, the rest of the configuration is the same. Thus the new
+    agent can use the old configuration files by just adding the the "metadata"
+    plugable extension.