[cbf] Fix cbf sync error (#2056)

What I did
Changed the CBF group members sync code to be non-assertive when one of its members is not yet synced.

Why I did it
There can be situations when the member of a CBF group is not yet synced by the time the CBF group is being synced. Some examples would be:

CBF group entry is created before its member in APPL_DB
Member sync is being blocked by something, like missing a neighbor/NH entry
In this scenarios, we should wait for the member to be synced instead of asserting as the member might become available shortly.

How I verified it
Added a new UT

orchagent/cbf/cbfnhgorch.cpp

@@ -632,6 +632,11 @@ bool CbfNhg::syncMembers(const set<string> &members)
                            nhgm.to_string().c_str(), to_string().c_str());
             throw std::logic_error("Syncing already synced NHG member");
         }
+        else if (nhgm.getNhgId() == SAI_NULL_OBJECT_ID)
+        {
+            SWSS_LOG_WARN("CBF NHG member %s is not yet synced", nhgm.to_string().c_str());
+            return false;
+        }
 
         /*
          * Check if the group exists in NhgOrch.
@@ -710,10 +715,9 @@ vector<sai_attribute_t> CbfNhg::createNhgmAttrs(const CbfNhgMember &nhgm) const
 {
     SWSS_LOG_ENTER();
 
-    if (!isSynced() || (nhgm.getNhgId() == SAI_NULL_OBJECT_ID))
+    if (!isSynced())
     {
-        SWSS_LOG_ERROR("CBF next hop group %s or next hop group %s are not synced",
-                       to_string().c_str(), nhgm.to_string().c_str());
+        SWSS_LOG_ERROR("CBF next hop group %s is not synced", to_string().c_str());
         throw logic_error("CBF next hop group member attributes data is insufficient");
     }
 

tests/test_nhg.py

@@ -2207,6 +2207,42 @@ def create_cbf_nhg_inexistent_map_test():
             self.fc_to_nhg_ps._del(nhg_maps.pop())
         self.asic_db.wait_for_n_keys(self.ASIC_NHG_MAP_STR, self.asic_nhg_maps_count)
 
+    # Test scenario:
+    # - Create a CBF NHG that has a member which is not yet synced. It shouldn't be synced.
+    # - Add the missing member and assert the CBF NHG is now synced.
+    def test_cbf_sync_before_member(self, dvs, testlog):
+        self.init_test(dvs, 2)
+
+        # Create an FC to NH index selection map
+        nhg_map = [(str(i), '0' if i < 4 else '1') for i in range(8)]
+        fvs = swsscommon.FieldValuePairs(nhg_map)
+        self.fc_to_nhg_ps.set('cbfnhgmap1', fvs)
+        self.asic_db.wait_for_n_keys(self.ASIC_NHG_MAP_STR, self.asic_nhg_maps_count + 1)
+
+        # Create a non-CBF NHG
+        fvs = swsscommon.FieldValuePairs([('nexthop', '10.0.0.1,10.0.0.3'),
+                                            ('ifname', 'Ethernet0,Ethernet4')])
+        self.nhg_ps.set('group1', fvs)
+        self.asic_db.wait_for_n_keys(self.ASIC_NHG_STR, self.asic_nhgs_count + 1)
+
+        # Create a CBF NHG with a member that doesn't currently exist. Nothing should happen
+        fvs = swsscommon.FieldValuePairs([('members', 'group1,group2'),
+                                        ('selection_map', 'cbfnhgmap1')])
+        self.cbf_nhg_ps.set('cbfgroup1', fvs)
+        time.sleep(1)
+        assert(len(self.asic_db.get_keys(self.ASIC_NHG_STR)) == self.asic_nhgs_count + 1)
+
+        # Create the missing non-CBF NHG. This and the CBF NHG should be created.
+        fvs = swsscommon.FieldValuePairs([('nexthop', '10.0.0.1,10.0.0.3'),
+                                        ("ifname", "Ethernet0,Ethernet4")])
+        self.nhg_ps.set("group2", fvs)
+        self.asic_db.wait_for_n_keys(self.ASIC_NHG_STR, self.asic_nhgs_count + 3)
+
+        # Cleanup
+        self.nhg_ps._del('cbfgroup1')
+        self.nhg_ps._del('group1')
+        self.nhg_ps._del('group2')
+        self.nhg_ps._del('cbfnhgmap1')
 
 # Add Dummy always-pass test at end as workaroud
 # for issue when Flaky fail on final test it invokes module tear-down before retrying