lib/ovsdb: Allow interface to work with CMR

The interface code curretly strictly gates operation based on
information from `goal-state`.  This information is however not
available when used with CMR.

Since the ovn-central charm currently must be at least 3 units,
we can assume a minimum of 3 units to be joined when the expected
count from `goal-state` is 1.

Also replace os-testr with stestr.

Closes-Bug: #1976537
Change-Id: I5b91d3caa466383fec76a393556668eb3b59ec63

src/lib/ovsdb.py

@@ -156,9 +156,15 @@ class OVSDB(reactive.Endpoint):
                   False otherwise.
         :rtype: bool
         """
-        if len(self.all_joined_units) == len(
-                list(ch_core.hookenv.expected_related_units(
-                    self.expand_name('{endpoint_name}')))):
+        expected_related_units = len(
+            list(ch_core.hookenv.expected_related_units(
+                self.expand_name('{endpoint_name}'))))
+        # A minimum of 3 ovn-central units are required for operation, if
+        # this number is 1 chances are we are consuming the realation over CMR
+        # which would not provide us with an accurate number.
+        if expected_related_units == 1:
+            expected_related_units = 3
+        if len(self.all_joined_units) >= expected_related_units:
             bound_addrs = [unit.received.get('bound-address', None) is not None
                            for relation in self.relations
                            for unit in relation.units]

test-requirements.txt

@@ -1,6 +1,6 @@
 # Lint and unit test requirements
 flake8
-os-testr>=0.4.1
+stestr
 charms.reactive
 mock>=1.2
 coverage>=3.6

tox.ini

@@ -13,17 +13,17 @@ install_command =
 [testenv:py3]
 basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:py35]
 basepython = python3.5
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:py36]
 basepython = python3.6
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:pep8]
 basepython = python3

unit_tests/test_lib_ovsdb.py

@@ -183,6 +183,18 @@ class TestOVSDBLib(test_utils.PatchHelper):
         unit3.received = {'bound-address': '6.7.8.9'}
         self.assertEquals(self.target.expected_units_available(), True)
 
+        # when related to ovn-central through CMR expected_related_units
+        # will always be 1.  check that this works
+        self.expected_related_units.return_value = [
+            'controller:user/offer.name',
+        ]
+        self.target._all_joined_units = [
+            'unit/0', 'unit/1']
+        self.assertEquals(self.target.expected_units_available(), False)
+        self.target._all_joined_units = [
+            'unit/0', 'unit/1', 'unit/2']
+        self.assertEquals(self.target.expected_units_available(), True)
+
     def test_publish_cluster_local_addr(self):
         to_publish = self.patch_topublish()
         self.target.publish_cluster_local_addr()