[show priority-group drop counters] Add user info output when user wa…

…nt to check PG counters and polling are disabled (sonic-net#1678)

Signed-off-by: Andriy Yurkiv <ayurkiv@nvidia.com>

What I did
Added additional output info for user when trying to show priority group counters and pg drop counters are disabled

How I did it
modify pg-drop script, add additional print during executing "show priority-group drop counters" if PG polling disabled

How to verify it
counterpoll pg-drop disable
show priority-group drop counters

Expect:
Warning: PG counters are disabled. Current stats may be outdated. Use 'counterpoll pg-drop enable' to enable'

Previous command output (if the output of a command-line utility has changed)
admin@r-tigon-04:/usr/local/bin$ show priority-group drop counters
Ingress PG dropped packets:
       Port    PG0    PG1    PG2    PG3    PG4    PG5    PG6    PG7
-----------  -----  -----  -----  -----  -----  -----  -----  -----
  Ethernet0      0      0      0      0      0      0      0      0
  Ethernet2      0      0      0      0      0      0      0      0
  Ethernet8      0      0      0      0      0      0      0      0
 Ethernet10      0      0      0      0      0      0      0      0
 Ethernet16      0      0      0      0      0      0      0      0

New command output (if the output of a command-line utility has changed)
admin@r-tigon-04:/usr/local/bin$ show priority-group drop counters
Warning: PG counters are disabled. Use 'counterpoll pg-drop enable' to enable polling

scripts/pg-drop

@@ -26,7 +26,7 @@ try:
 except KeyError:
     pass
 
-from swsscommon.swsscommon import SonicV2Connector
+from swsscommon.swsscommon import ConfigDBConnector, SonicV2Connector
 
 STATUS_NA = 'N/A'
 
@@ -47,6 +47,9 @@ class PgDropStat(object):
         self.counters_db = SonicV2Connector(host='127.0.0.1')
         self.counters_db.connect(self.counters_db.COUNTERS_DB)
 
+        self.configdb = ConfigDBConnector()
+        self.configdb.connect()
+
         dropstat_dir = get_dropstat_dir()
         self.port_drop_stats_file = os.path.join(dropstat_dir, 'pg_drop_stats')
 
@@ -212,6 +215,14 @@ class PgDropStat(object):
             sys.exit(e.errno)
         print("Cleared PG drop counter")
 
+    def check_if_stats_enabled(self):
+        pg_drop_info = self.configdb.get_entry('FLEX_COUNTER_TABLE', 'PG_DROP')
+        if pg_drop_info:
+            status = pg_drop_info.get("FLEX_COUNTER_STATUS", 'disable')
+            if status == "disable":
+                print("Warning: PG counters are disabled. Use 'counterpoll pg-drop enable' to enable polling")
+                sys.exit(0)
+
 def main():
     parser = argparse.ArgumentParser(description='Display PG drop counter',
                                      formatter_class=argparse.RawTextHelpFormatter,
@@ -240,6 +251,7 @@ pg-drop -c clear
     if command == 'clear':
         pgdropstat.clear_drop_counts()
     elif command == 'show':
+        pgdropstat.check_if_stats_enabled()
         pgdropstat.print_all_stat(COUNTER_TABLE_PREFIX, "pg_drop" )
     else:
         print("Command not recognized")

tests/pgdrop_input/config_db.json

@@ -0,0 +1,26 @@
+{
+    "FLEX_COUNTER_TABLE|QUEUE": {
+        "POLL_INTERVAL": "10000",
+        "FLEX_COUNTER_STATUS": "enable"
+    },
+    "FLEX_COUNTER_TABLE|PORT": {
+        "POLL_INTERVAL": "1000",
+        "FLEX_COUNTER_STATUS": "enable"
+    },
+    "FLEX_COUNTER_TABLE|PORT_BUFFER_DROP": {
+        "POLL_INTERVAL": "60000",
+        "FLEX_COUNTER_STATUS": "enable"
+    },
+    "FLEX_COUNTER_TABLE|QUEUE_WATERMARK": {
+        "POLL_INTERVAL": "10000",
+        "FLEX_COUNTER_STATUS": "enable"
+    },
+    "FLEX_COUNTER_TABLE|PG_WATERMARK": {
+        "POLL_INTERVAL": "10000",
+        "FLEX_COUNTER_STATUS": "enable"
+    },
+    "FLEX_COUNTER_TABLE|PG_DROP": {
+        "POLL_INTERVAL": "10000",
+        "FLEX_COUNTER_STATUS": "disable"
+    }
+}

tests/pgdropstat_test.py

@@ -1,11 +1,13 @@
 import os
 import sys
+import pytest
 
 import show.main as show
 import clear.main as clear
 import config.main as config
 
 from click.testing import CliRunner
+from shutil import copyfile
 
 test_path = os.path.dirname(os.path.abspath(__file__))
 modules_path = os.path.dirname(test_path)
@@ -39,6 +41,29 @@ def setup_class(cls):
         os.environ['UTILITIES_UNIT_TESTING'] = "2"
         print("SETUP")
 
+    @pytest.fixture(scope='function')
+    def replace_config_db_file(self):
+        sample_config_db_file = os.path.join(test_path, "pgdrop_input", "config_db.json")
+        mock_config_db_file = os.path.join(test_path, "mock_tables", "config_db.json")
+
+        #Backup origin config_db and replace it with config_db file with disabled PG_DROP counters 
+        copyfile(mock_config_db_file, "/tmp/config_db.json")
+        copyfile(sample_config_db_file, mock_config_db_file)
+
+        yield
+
+        copyfile("/tmp/config_db.json", mock_config_db_file)
+
+    def test_show_pg_drop_disabled(self, replace_config_db_file):
+        runner = CliRunner()
+
+        result = runner.invoke(show.cli.commands["priority-group"].commands["drop"].commands["counters"])
+        assert result.exit_code == 0
+        print(result.exit_code)
+
+        assert result.output == "Warning: PG counters are disabled. Use 'counterpoll pg-drop enable' to enable polling\n"
+        print(result.output)
+
     def test_show_pg_drop_show(self):
         self.executor(clear_before_show = False)