Fix swsscommon psubscribe code break in frrcfgd (sonic-net#13836)

Fix swsscommon psubscribe code break in frrcfgd

#### Why I did it
Fix frrcfgd psubscribe code break: sonic-net#13109
The code issue caused by API change when migrate from swsssdk to swsscommon

#### How I did it
Fix frrcfgd code to use swsscommon psubscribe API.

#### How to verify it
Pass all UT.
Manually check fixed code work correctly.

src/sonic-frr-mgmt-framework/frrcfgd/frrcfgd.py

@@ -1445,6 +1445,7 @@ class ExtConfigDBConnector(ConfigDBConnector):
     def __init__(self, ns_attrs = None):
         super(ExtConfigDBConnector, self).__init__()
         self.nosort_attrs = ns_attrs if ns_attrs is not None else {}
+        self.__listen_thread_running = False
     def raw_to_typed(self, raw_data, table = ''):
         if len(raw_data) == 0:
             raw_data = None
@@ -1469,12 +1470,28 @@ def sub_msg_handler(self, msg_item):
             except Exception as e:
                 syslog.syslog(syslog.LOG_ERR, '[bgp cfgd] Failed handling config DB update with exception:' + str(e))
                 logging.exception(e)
+
+    def listen_thread(self, timeout):
+        self.__listen_thread_running = True
+        sub_key_space = "__keyspace@{}__:*".format(self.get_dbid(self.db_name))
+        self.pubsub.psubscribe(sub_key_space)
+        while self.__listen_thread_running:
+            msg = self.pubsub.get_message(timeout, True)
+            if msg:
+                self.sub_msg_handler(msg)
+
+        self.pubsub.punsubscribe(sub_key_space)
+
     def listen(self):
         """Start listen Redis keyspace events and will trigger corresponding handlers when content of a table changes.
         """
         self.pubsub = self.get_redis_client(self.db_name).pubsub()
-        self.pubsub.psubscribe(**{"__keyspace@{}__:*".format(self.get_dbid(self.db_name)): self.sub_msg_handler})
-        self.sub_thread = self.pubsub.run_in_thread(sleep_time = 0.01)
+        self.sub_thread = threading.Thread(target=self.listen_thread, args=(0.01,))
+        self.sub_thread.start()
+
+    def stop_listen(self):
+        self.__listen_thread_running = False
+
     @staticmethod
     def get_table_key(table, key):
         return table + '&&' + key
@@ -3774,7 +3791,7 @@ def start(self):
         self.subscribe_all()
         self.config_db.listen()
     def stop(self):
-        self.config_db.sub_thread.stop()
+        self.config_db.stop_listen()
         if self.config_db.sub_thread.is_alive():
             self.config_db.sub_thread.join()
 

src/sonic-frr-mgmt-framework/tests/test_config.py

@@ -14,10 +14,10 @@ def test_contructor():
     for table, hdlr in daemon.table_handler_list:
         daemon.config_db.subscribe.assert_any_call(table, hdlr)
     daemon.config_db.pubsub.psubscribe.assert_called_once()
+    assert(daemon.config_db.sub_thread.is_alive() == True)
     daemon.stop()
-    daemon.config_db.sub_thread.stop.assert_called()
-    daemon.config_db.sub_thread.is_alive.assert_called_once()
-    daemon.config_db.sub_thread.join.assert_called_once()
+    daemon.config_db.pubsub.punsubscribe.assert_called_once()
+    assert(daemon.config_db.sub_thread.is_alive() == False)
 
 class CmdMapTestInfo:
     data_buf = {}