Add 'default' option for sFlow. (sonic-net#1606)

* Add 'default' option for sFlow.
Signed-off-by: Venkatesan Mahalingam <venkatesan_mahalinga@dell.com>

Author: venkatmahalingam

config/main.py

@@ -5018,7 +5018,7 @@ def polling_int(ctx, interval):
     config_db.mod_entry('SFLOW', 'global', sflow_tbl['global'])
 
 def is_valid_sample_rate(rate):
-    return rate in range(256, 8388608 + 1)
+    return rate.isdigit() and int(rate) in range(256, 8388608 + 1)
 
 
 #
@@ -5076,24 +5076,31 @@ def disable(ctx, ifname):
 #
 @interface.command('sample-rate')
 @click.argument('ifname', metavar='<interface_name>', required=True, type=str)
-@click.argument('rate', metavar='<sample_rate>', required=True, type=int)
+@click.argument('rate', metavar='<sample_rate>', required=True, type=str)
 @click.pass_context
 def sample_rate(ctx, ifname, rate):
     config_db = ctx.obj['db']
     if not interface_name_is_valid(config_db, ifname) and ifname != 'all':
         click.echo('Invalid interface name')
         return
-    if not is_valid_sample_rate(rate):
-        click.echo('Error: Sample rate must be between 256 and 8388608')
+    if not is_valid_sample_rate(rate) and rate != 'default':
+        click.echo('Error: Sample rate must be between 256 and 8388608 or default')
         return
 
     sess_dict = config_db.get_table('SFLOW_SESSION')
 
-    if sess_dict and ifname in sess_dict:
+    if sess_dict and ifname in sess_dict.keys():
+        if rate == 'default':
+            if 'sample_rate' not in sess_dict[ifname]:
+                return
+            del sess_dict[ifname]['sample_rate']
+            config_db.set_entry('SFLOW_SESSION', ifname, sess_dict[ifname])
+            return
         sess_dict[ifname]['sample_rate'] = rate
         config_db.mod_entry('SFLOW_SESSION', ifname, sess_dict[ifname])
     else:
-        config_db.mod_entry('SFLOW_SESSION', ifname, {'sample_rate': rate})
+        if rate != 'default':
+            config_db.mod_entry('SFLOW_SESSION', ifname, {'sample_rate': rate})
 
 
 #

tests/sflow_test.py

@@ -290,6 +290,45 @@ def test_config_enable_all_intf(self):
         sflowSession = db.cfgdb.get_table('SFLOW_SESSION')
         assert sflowSession["all"]["admin_state"] == "up"
 
+    def test_config_sflow_intf_sample_rate_default(self):
+        db = Db()
+        runner = CliRunner()
+        obj = {'db':db.cfgdb}
+
+        # mock interface_name_is_valid
+        config.interface_name_is_valid = mock.MagicMock(return_value = True)
+
+        result_out1 = runner.invoke(show.cli.commands["sflow"].commands["interface"], [], obj=Db())
+        print(result_out1.exit_code, result_out1.output)
+        assert result_out1.exit_code == 0
+        
+        # set sample-rate to 2500
+        result = runner.invoke(config.config.commands["sflow"].
+            commands["interface"].commands["sample-rate"],
+            ["Ethernet2", "2500"], obj=obj)
+        print(result.exit_code, result.output)
+        assert result.exit_code == 0
+
+        # we can not use 'show sflow interface', becasue 'show sflow interface'
+        # gets data from appDB, we need to fetch data from configDB for verification
+        sflowSession = db.cfgdb.get_table('SFLOW_SESSION')
+        assert sflowSession["Ethernet2"]["sample_rate"] == "2500"
+
+        # set sample-rate to default
+        result = runner.invoke(config.config.commands["sflow"].
+            commands["interface"].commands["sample-rate"],
+            ["Ethernet2", "default"], obj=obj)
+        print(result.exit_code, result.output)
+        assert result.exit_code == 0
+
+        result_out2 = runner.invoke(show.cli.commands["sflow"].commands["interface"], [], obj=Db())
+        print(result_out2.exit_code, result_out2.output)
+        assert result_out2.exit_code == 0
+        assert result_out1.output == result_out2.output
+
+        return
+
+
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")