Fixed TD-2499, ensuring crash_gen tool releases ALL DB connections when completing tests

tests/pytest/crash_gen/crash_gen_main.py

@@ -2224,22 +2224,25 @@ class ClientManager:
         if svcMgr: # gConfig.auto_start_service:
             svcMgr.stopTaosServices()
             svcMgr = None
+        
+
+        # Release global variables
+        gConfig = None
+        gSvcMgr = None
+        logger = None
+        
+        thPool = None
+        dbManager.cleanUp() # destructor wouldn't run in time
+        dbManager = None
+
         # Print exec status, etc., AFTER showing messages from the server
         self.conclude()
         # print("TC failed (2) = {}".format(self.tc.isFailed()))
         # Linux return code: ref https://shapeshed.com/unix-exit-codes/
         ret = 1 if self.tc.isFailed() else 0
         self.tc.cleanup()
-
-        # Release global variables
-        gConfig = None
-        gSvcMgr = None
-        logger = None
-
         # Release variables here
         self.tc = None
-        thPool = None
-        dbManager = None
 
         gc.collect() # force garbage collection
         # h = hpy()

tests/pytest/crash_gen/db.py

@@ -394,6 +394,7 @@ class DbManager():
             cType == 'native') else DbConn.createRest(dbTarget)
         try:
             self._dbConn.open()  # may throw taos.error.ProgrammingError: disconnected
+            Logging.debug("DbManager opened DB connection...")
         except taos.error.ProgrammingError as err:
             # print("Error type: {}, msg: {}, value: {}".format(type(err), err.msg, err))
             if (err.msg == 'client disconnected'):  # cannot open DB connection
@@ -412,6 +413,10 @@ class DbManager():
         # Moved to Database()
         # self._stateMachine = StateMechine(self._dbConn)
 
+    def __del__(self):
+        ''' Release the underlying DB connection upon deletion of DbManager '''
+        self.cleanUp()
+
     def getDbConn(self):
         return self._dbConn
 
@@ -438,5 +443,8 @@ class DbManager():
         return "table_{}".format(tblNum)
 
     def cleanUp(self):
-        self._dbConn.close()
+        if self._dbConn:
+            self._dbConn.close()
+            self._dbConn = None
+            Logging.debug("DbManager closed DB connection...")