[stable] Make version pinning optional

The OVN charms prepared for the upgrade from OVN 20.03 to newer
versions by unconditionally enabling version pinning.

Since then we have reached agreement with upstream that rolling
upgrades should work when upgrading within the previous upstream
LTS version and the next.

Having the pinning enabled may cause unnecessary grief for anyone
already upgraded to OVN 22.03.

Add a charm configuration option to allow controlling the version
pinning.

Closes-Bug: #2030944
Signed-off-by: Frode Nordahl <[email protected]>
(cherry picked from commit f68ecbd)
(cherry picked from commit 2a61104)
(cherry picked from commit bde8c8c)

config.yaml

@@ -305,3 +305,19 @@ options:
       .
       Changing this config option will restart openvswitch-switch, resulting
       in an expected data plane outage while the service restarts.
+  enable-version-pinning:
+    type: boolean
+    default: true
+    description: |
+      OVN is a distributed system, and special consideration must be given to
+      the process used to upgrade OVN.
+
+      In order to successfully perform a rolling upgrade, the ovn-controller
+      process needs to understand the structure of the database for the version
+      you are upgrading from and to simultaneously.
+
+      Rolling upgrades are supported as long as the span of versions used in
+      the system is within the previous and the next upstream OVN LTS version.
+
+      If you are upgrading across LTS boundaries you may need to use version
+      pinning to avoid data plane outage during the upgrade.

lib/charms/ovn_charm.py

@@ -793,7 +793,8 @@ def configure_ovs(self, sb_conn, mlockall_changed):
                            'external-ids:system-id={}'
                            .format(self.get_ovs_hostname()),
                            'external-ids:ovn-remote={}'.format(sb_conn),
-                           'external_ids:ovn-match-northd-version=true',
+                           'external_ids:ovn-match-northd-version={}'
+                           .format(self.options.enable_version_pinning),
                            ):
             cmd = cmd + ('--', 'set', 'open-vswitch', '.', ovs_ext_id)
         self.run(*cmd)

unit_tests/test_lib_charms_ovn_charm.py

@@ -770,7 +770,7 @@ def test_configure_bridges(self):
 class TestOVNChassisCharm(Helper):
 
     def setUp(self):
-        super().setUp(config={
+        self.local_config = {
             'enable-hardware-offload': False,
             'enable-sriov': False,
             'enable-dpdk': False,
@@ -779,7 +779,8 @@ def setUp(self):
             'ovn-bridge-mappings': (
                 'provider:br-provider other:br-other'),
             'prefer-chassis-as-gw': True,
-        })
+            'enable-version-pinning': False}
+        super().setUp(config=self.local_config)
 
     def test_optional_openstack_metadata(self):
         self.assertEquals(self.target.packages, ['ovn-host'])
@@ -915,7 +916,7 @@ def test_configure_ovs(self):
                 '--', 'set', 'open-vswitch', '.',
                 'external-ids:ovn-remote=fake-sb-conn-str',
                 '--', 'set', 'open-vswitch', '.',
-                'external_ids:ovn-match-northd-version=true',
+                'external_ids:ovn-match-northd-version=False',
             ),
         ])
         self.service_restart.assert_not_called()
@@ -941,7 +942,7 @@ def test_configure_ovs(self):
                 '--', 'set', 'open-vswitch', '.',
                 'external-ids:ovn-remote=fake-sb-conn-str',
                 '--', 'set', 'open-vswitch', '.',
-                'external_ids:ovn-match-northd-version=true',
+                'external_ids:ovn-match-northd-version=False',
             ),
             mock.call('ovs-vsctl', '--id', '@manager',
                       'create', 'Manager', 'target="ptcp:6640:127.0.0.1"',
@@ -950,6 +951,39 @@ def test_configure_ovs(self):
         ])
         assert self.service_restart.called
 
+    def test_configure_ovs_version_pinning(self):
+        self.local_config.update({'enable-version-pinning': True})
+        self.target = ovn_charm.BaseOVNChassisCharm()
+        self.patch_target('run')
+        self.patch_object(ovn_charm.OVNConfigurationAdapter, 'ovn_key')
+        self.patch_object(ovn_charm.OVNConfigurationAdapter, 'ovn_cert')
+        self.patch_object(ovn_charm.OVNConfigurationAdapter, 'ovn_ca_cert')
+        self.patch_object(ovn_charm.ch_core.host, 'service_restart')
+        self.patch_target('get_data_ip')
+        self.get_data_ip.return_value = 'fake-data-ip'
+        self.patch_target('get_ovs_hostname')
+        self.get_ovs_hostname.return_value = 'fake-ovs-hostname'
+        self.patch_target('check_if_paused')
+        self.check_if_paused.return_value = (None, None)
+        self.target.configure_ovs('fake-sb-conn-str', False)
+        self.run.assert_has_calls([
+            mock.call('ovs-vsctl', '--no-wait', 'set-ssl',
+                      mock.ANY, mock.ANY, mock.ANY),
+            mock.call(
+                'ovs-vsctl',
+                '--', 'set', 'open-vswitch', '.',
+                'external-ids:ovn-encap-type=geneve',
+                '--', 'set', 'open-vswitch', '.',
+                'external-ids:ovn-encap-ip=fake-data-ip',
+                '--', 'set', 'open-vswitch', '.',
+                'external-ids:system-id=fake-ovs-hostname',
+                '--', 'set', 'open-vswitch', '.',
+                'external-ids:ovn-remote=fake-sb-conn-str',
+                '--', 'set', 'open-vswitch', '.',
+                'external_ids:ovn-match-northd-version=True',
+            ),
+        ])
+
     def test_render_nrpe(self):
         self.patch_object(ovn_charm.nrpe, 'NRPE')
         self.patch_object(ovn_charm.nrpe, 'add_init_service_checks')