[pbh]: Fix show PBH counters when cache is partial (sonic-net#3356)

* [pbh]: Fix show PBH counters when cache is partial.

Signed-off-by: Nazarii Hnydyn <[email protected]>

show/plugins/pbh.py

@@ -395,7 +395,7 @@ def get_counter_value(pbh_counters, saved_pbh_counters, key, type):
     if not pbh_counters[key]:
         return '0'
 
-    if key in saved_pbh_counters:
+    if key in saved_pbh_counters and saved_pbh_counters[key]:
         new_value = int(pbh_counters[key][type]) - int(saved_pbh_counters[key][type])
         if new_value >= 0:
             return str(new_value)

tests/pbh_input/assert_show_output.py

@@ -78,6 +78,14 @@
 """
 
 
+show_pbh_statistics_partial = """\
+TABLE       RULE    RX PACKETS COUNT    RX BYTES COUNT
+----------  ------  ------------------  ----------------
+pbh_table1  nvgre   100                 200
+pbh_table2  vxlan   0                   0
+"""
+
+
 show_pbh_statistics_updated="""\
 TABLE       RULE    RX PACKETS COUNT    RX BYTES COUNT
 ----------  ------  ------------------  ----------------

tests/pbh_input/counters_db_partial.json

@@ -0,0 +1,11 @@
+{
+    "COUNTERS:oid:0x9000000000000": { },
+    "COUNTERS:oid:0x9000000000001": {
+        "SAI_ACL_COUNTER_ATTR_PACKETS": "300",
+        "SAI_ACL_COUNTER_ATTR_BYTES": "400"
+    },
+    "ACL_COUNTER_RULE_MAP": {
+        "pbh_table1:nvgre": "oid:0x9000000000000",
+        "pbh_table2:vxlan": "oid:0x9000000000001"
+    }
+}

tests/pbh_test.py

@@ -946,6 +946,34 @@ def test_show_pbh_statistics_after_clear(self):
         assert result.exit_code == SUCCESS
         assert result.output == assert_show_output.show_pbh_statistics_zero
 
+    def test_show_pbh_statistics_after_clear_and_counters_partial(self):
+        dbconnector.dedicated_dbs['COUNTERS_DB'] = os.path.join(mock_db_path, 'counters_db_partial')
+        dbconnector.dedicated_dbs['CONFIG_DB'] = os.path.join(mock_db_path, 'full_pbh_config')
+
+        self.remove_pbh_counters_file()
+
+        db = Db()
+        runner = CliRunner()
+
+        result = runner.invoke(
+            clear.cli.commands["pbh"].
+            commands["statistics"], [], obj=db
+        )
+
+        logger.debug("\n" + result.output)
+        logger.debug(result.exit_code)
+
+        dbconnector.dedicated_dbs['COUNTERS_DB'] = os.path.join(mock_db_path, 'counters_db')
+
+        result = runner.invoke(
+            show.cli.commands["pbh"].
+            commands["statistics"], [], obj=db
+        )
+
+        logger.debug("\n" + result.output)
+        logger.debug(result.exit_code)
+        assert result.exit_code == SUCCESS
+        assert result.output == assert_show_output.show_pbh_statistics_partial
 
     def test_show_pbh_statistics_after_clear_and_counters_updated(self):
         dbconnector.dedicated_dbs['COUNTERS_DB'] = os.path.join(mock_db_path, 'counters_db')