Add nbd kernel module for snapshot mounts

Add nbd kernel module for mounting snapshots.

Closes-Bug: 1961149
Change-Id: I59a8a02db3326026f58a775649b63935254b6cf6

src/reactive/data_mover_handlers.py

@@ -12,6 +12,9 @@
 
 import charms_openstack.charm as charm
 import charms.reactive as reactive
+import charmhelpers.core.kernel as ch_kernel
+import charmhelpers.core.host as ch_host
+import charmhelpers.core.hookenv as ch_hookenv
 
 # This charm's library contains all of the handler code associated with
 # trilio_dm
@@ -38,6 +41,23 @@ def render_config(*args):
     reactive.set_state("config.rendered")
 
 
+@reactive.when_not('is-update-status-hook')
+@reactive.when('charm.installed')
+def setup_kernel_modules():
+    module = 'nbd'
+    if ch_host.is_container():
+        ch_hookenv.log(
+            "Cannot load modules inside of a container",
+            level=ch_hookenv.WARNING)
+    else:
+        try:
+            ch_kernel.modprobe(module)
+        except Exception:
+            ch_hookenv.log(
+                "Failed to load kernel module '%s'" % module,
+                level=ch_hookenv.WARNING)
+
+
 @reactive.when('shared-db.connected')
 def default_setup_database(database):
     """Handle the default database connection setup

unit_tests/__init__.py

@@ -7,3 +7,5 @@ sys.path.append("src/lib")
 import charms_openstack.test_mocks  # noqa
 
 charms_openstack.test_mocks.mock_charmhelpers()
+sys.modules['charmhelpers.core.kernel'] = (
+    charms_openstack.test_mocks.charmhelpers.core.kernel)

unit_tests/test_data_mover.py

@@ -93,11 +93,17 @@ class Test(test_utils.PatchHelper):
             "ceph_connected": (
                 "ceph.connected",
             ),
+            "setup_kernel_modules": (
+                "charm.installed",
+            ),
         }
         when_not_patterns = {
             "ceph_connected": (
                 "ceph.access.req.sent",
             ),
+            "setup_kernel_modules": (
+                "is-update-status-hook",
+            ),
         }
         # check the when hooks are attached to the expected functions
         for t, p in [