Raise an exc if no VIP/backend is available

When deploying Manila CephFS NFS with cephadm,
the manila share service fails to start with the error
"Backend cephfsnfs supports neither IPv4 nor IPv6".

This happens because the NFS Ganesha daemon fails
to start for some reason and therefore the driver never
gets the location of the NFS Ganesha service
that will be used as the backend.

We should raise an error in this case with more information
about the failure.

This change adds this to the NFSClusterProtocol helper.

Closes-Bug: #1990150

Change-Id: Ic74c6c9d9770974848ec9dfb6d2225ce9b3bcb52

manila/share/drivers/cephfs/driver.py

@@ -1196,6 +1196,13 @@ class NFSClusterProtocolHelper(NFSProtocolHelperMixin, ganesha.NASHelperBase):
         else:
             export_ips.append(vip)
 
+        # there are no export IPs, there are no NFS servers we can use
+        if not export_ips:
+            msg = _("There are no NFS servers available to use. "
+                    "Please check the health of your Ceph cluster "
+                    "and restart the manila share service.")
+            raise exception.ShareBackendException(msg=msg)
+
         return export_ips
 
     def check_for_setup_error(self):

manila/tests/share/drivers/cephfs/test_driver.py

@@ -1265,6 +1265,27 @@ class NFSClusterProtocolHelperTestCase(test.TestCase):
         type(self._nfscluster_protocol_helper).nfs_clusterid = (
             mock.PropertyMock(return_value='fs-manila'))
 
+    def test_get_export_ips_no_backends(self):
+        fake_conf = configuration.Configuration(None)
+        cluster_info = {
+            "fs-manila": {
+                "virtual_ip": None,
+                "backend": []
+            }
+        }
+
+        driver.rados_command.return_value = json.dumps(cluster_info)
+
+        helper = driver.NFSClusterProtocolHelper(
+            self._execute,
+            fake_conf,
+            rados_client=self._rados_client,
+            volname=self._volname
+        )
+
+        self.assertRaises(exception.ShareBackendException,
+                          helper._get_export_ips)
+
     @ddt.data(constants.ACCESS_LEVEL_RW, constants.ACCESS_LEVEL_RO)
     def test_allow_access_rw_ro(self, mode):
         access_allow_prefix = "nfs export apply"

releasenotes/notes/bug-1990150-cephadm-cephnfs-backend-fails-start-raise-exc-7459302bf662fdd6.yaml

@@ -0,0 +1,12 @@
+---
+fixes:
+  - |
+    When deploying Manila CephFS NFS with cephadm, the manila share
+    service fails to start with the error "Backend cephfsnfs supports
+    neither IPv4 nor IPv6". This happens because the NFS Ganesha
+    daemon fails to start for some reason, and therefore the driver
+    never gets the location of the NFS Ganesha service that will be
+    used as the backend. We rely on the operator to make sure the CephFS
+    NFS cluster is available when initializing the driver. With this fix in
+    place, we raise an exception to explicitly notify the operator and
+    allow them to take further action.