Warn in status if tune-osd-memory-target invalid

This is useful, because if an invalid value is set,
the value is ignored and not overridden,
and an error logged.
So now we warn about this in the status to be more obvious to the user.

Change-Id: Idc4a7706f30cbcea8aee83a1406fa84139fe510d

hooks/ceph_hooks.py

@@ -386,6 +386,18 @@ def warn_if_memory_outside_bounds(value):
             "This is not recommended.", level=WARNING)
 
 
+def is_tune_osd_memory_target_valid() -> bool:
+    """
+    Check if the tune-osd-memory-target value is valid
+
+    :returns: True if valid, else False
+    :rtype: bool
+    """
+    # NOTE: keep this logic in sync with get_osd_memory_target()
+    value = config('tune-osd-memory-target')
+    return not value or bool(re.match(r"\d+(?:GB|%)$", value))
+
+
 def get_osd_memory_target():
     """
     Processes the config value of tune-osd-memory-target.
@@ -868,6 +880,11 @@ VERSION_PACKAGE = 'ceph-common'
 
 def assess_status():
     """Assess status of current unit"""
+
+    if not is_tune_osd_memory_target_valid():
+        status_set('blocked', 'tune-osd-memory-target config value is invalid')
+        return
+
     # check to see if the unit is paused.
     application_version_set(get_upstream_version(VERSION_PACKAGE))
     if is_unit_upgrading_set():

unit_tests/test_ceph_hooks.py

@@ -737,6 +737,38 @@ class CephHooksTestCase(unittest.TestCase):
             level=ceph_hooks.WARNING
         )
 
+    @patch.object(ceph_hooks, "config")
+    def test_is_tune_osd_memory_target_valid(self, mock_config):
+        def tune(value):
+            return lambda k: (
+                value if k == "tune-osd-memory-target" else KeyError
+            )
+
+        # value, is_valid
+        scenarios = [
+            ("", True),
+            ("5GB", True),
+            ("020GB", True),
+            ("34GB", True),
+            ("5%", True),
+            ("05%", True),
+            ("50%", True),
+            ("test", False),
+            ("   ", False),
+            ("5", False),
+            ("GB", False),
+            ("%", False),
+            ("test5GB", False),
+            ("50%%", False),
+        ]
+        for value, expected_valid in scenarios:
+            mock_config.side_effect = tune(value)
+            print(f"testing tune-osd-memory-target set to {value}")
+            self.assertEqual(
+                ceph_hooks.is_tune_osd_memory_target_valid(),
+                expected_valid
+            )
+
     @patch.object(ceph_hooks, "config")
     @patch.object(ceph_hooks, "get_total_ram")
     @patch.object(ceph_hooks, "kv")