crash_gen.py

#-----!/usr/bin/python3.7
###################################################################
#           Copyright (c) 2016 by TAOS Technologies, Inc.
#                     All rights reserved.
#
#  This file is proprietary and confidential to TAOS Technologies.
#  No part of this file may be reproduced, stored, transmitted,
#  disclosed or used in any form or by any means other than as
#  expressly provided by the written permission from Jianhui Tao
#
###################################################################

# -*- coding: utf-8 -*-
from __future__ import annotations  # For type hinting before definition, ref: https://stackoverflow.com/questions/33533148/how-do-i-specify-that-the-return-type-of-a-method-is-the-same-as-the-class-itsel    

import sys
import os
import io
import signal
import traceback
# Require Python 3
if sys.version_info[0] < 3:
    raise Exception("Must be using Python 3")

import getopt
import argparse
import copy
import requests

import threading
import random
import time
import logging
import datetime
import textwrap
import requests
from requests.auth import HTTPBasicAuth

from typing import List
from typing import Dict
from typing import Set
from typing import IO
from queue import Queue, Empty

from util.log import *
from util.dnodes import *
from util.cases import *
from util.sql import *

import crash_gen
import taos

# Global variables, tried to keep a small number. 

# Command-line/Environment Configurations, will set a bit later
# ConfigNameSpace = argparse.Namespace
gConfig = argparse.Namespace() # Dummy value, will be replaced later
logger = None

def runThread(wt: WorkerThread):    
    wt.run()

class CrashGenError(Exception):
    def __init__(self, msg=None, errno=None):
        self.msg = msg    
        self.errno = errno
    
    def __str__(self):
        return self.msg

class WorkerThread:
    def __init__(self, pool: ThreadPool, tid, 
            tc: ThreadCoordinator,
            # te: TaskExecutor,
            ): # note: main thread context!
        # self._curStep = -1 
        self._pool = pool
        self._tid = tid        
        self._tc = tc # type: ThreadCoordinator
        # self.threadIdent = threading.get_ident()
        self._thread = threading.Thread(target=runThread, args=(self,))
        self._stepGate = threading.Event()

        # Let us have a DB connection of our own
        if ( gConfig.per_thread_db_connection ): # type: ignore
            # print("connector_type = {}".format(gConfig.connector_type))
            self._dbConn = DbConn.createNative() if (gConfig.connector_type == 'native') else DbConn.createRest()

        self._dbInUse = False # if "use db" was executed already

    def logDebug(self, msg):
        logger.debug("    TRD[{}] {}".format(self._tid, msg))

    def logInfo(self, msg):
        logger.info("    TRD[{}] {}".format(self._tid, msg))

    def dbInUse(self):
        return self._dbInUse

    def useDb(self):
        if ( not self._dbInUse ):
            self.execSql("use db")
        self._dbInUse = True

    def getTaskExecutor(self):
        return self._tc.getTaskExecutor()     

    def start(self):
        self._thread.start()  # AFTER the thread is recorded

    def run(self): 
        # initialization after thread starts, in the thread context
        # self.isSleeping = False
        logger.info("Starting to run thread: {}".format(self._tid))

        if ( gConfig.per_thread_db_connection ): # type: ignore
            logger.debug("Worker thread openning database connection")
            self._dbConn.open()

        self._doTaskLoop()       
        
        # clean up
        if ( gConfig.per_thread_db_connection ): # type: ignore 
            self._dbConn.close()

    def _doTaskLoop(self) :
        # while self._curStep < self._pool.maxSteps:
        # tc = ThreadCoordinator(None)
        while True:  
            tc = self._tc # Thread Coordinator, the overall master            
            tc.crossStepBarrier()  # shared barrier first, INCLUDING the last one
            logger.debug("[TRD] Worker thread [{}] exited barrier...".format(self._tid))
            self.crossStepGate()   # then per-thread gate, after being tapped
            logger.debug("[TRD] Worker thread [{}] exited step gate...".format(self._tid))
            if not self._tc.isRunning():
                logger.debug("[TRD] Thread Coordinator not running any more, worker thread now stopping...")
                break

            # Fetch a task from the Thread Coordinator
            logger.debug("[TRD] Worker thread [{}] about to fetch task".format(self._tid))
            task = tc.fetchTask()

            # Execute such a task
            logger.debug("[TRD] Worker thread [{}] about to execute task: {}".format(self._tid, task.__class__.__name__))
            task.execute(self)
            tc.saveExecutedTask(task)
            logger.debug("[TRD] Worker thread [{}] finished executing task".format(self._tid))

            self._dbInUse = False # there may be changes between steps
  
    def verifyThreadSelf(self): # ensure we are called by this own thread
        if ( threading.get_ident() != self._thread.ident ): 
            raise RuntimeError("Unexpectly called from other threads")

    def verifyThreadMain(self): # ensure we are called by the main thread
        if ( threading.get_ident() != threading.main_thread().ident ): 
            raise RuntimeError("Unexpectly called from other threads")

    def verifyThreadAlive(self):
        if ( not self._thread.is_alive() ):
            raise RuntimeError("Unexpected dead thread")

    # A gate is different from a barrier in that a thread needs to be "tapped"
    def crossStepGate(self):
        self.verifyThreadAlive()
        self.verifyThreadSelf() # only allowed by ourselves
        
        # Wait again at the "gate", waiting to be "tapped"
        logger.debug("[TRD] Worker thread {} about to cross the step gate".format(self._tid))
        self._stepGate.wait() 
        self._stepGate.clear()
        
        # self._curStep += 1  # off to a new step...

    def tapStepGate(self): # give it a tap, release the thread waiting there
        self.verifyThreadAlive()
        self.verifyThreadMain() # only allowed for main thread
 
        logger.debug("[TRD] Tapping worker thread {}".format(self._tid))
        self._stepGate.set() # wake up!        
        time.sleep(0) # let the released thread run a bit

    def execSql(self, sql): # TODO: expose DbConn directly
        if ( gConfig.per_thread_db_connection ):
            return self._dbConn.execute(sql)            
        else:
            return self._tc.getDbManager().getDbConn().execute(sql)

    def querySql(self, sql): # TODO: expose DbConn directly
        if ( gConfig.per_thread_db_connection ):
            return self._dbConn.query(sql)            
        else:
            return self._tc.getDbManager().getDbConn().query(sql)

    def getQueryResult(self):
        if ( gConfig.per_thread_db_connection ):
            return self._dbConn.getQueryResult()       
        else:
            return self._tc.getDbManager().getDbConn().getQueryResult()

    def getDbConn(self):
        if ( gConfig.per_thread_db_connection ):
            return self._dbConn     
        else:
            return self._tc.getDbManager().getDbConn()

    # def querySql(self, sql): # not "execute", since we are out side the DB context
    #     if ( gConfig.per_thread_db_connection ):
    #         return self._dbConn.query(sql)            
    #     else:
    #         return self._tc.getDbState().getDbConn().query(sql)

# The coordinator of all worker threads, mostly running in main thread
class ThreadCoordinator:
    def __init__(self, pool: ThreadPool, dbManager):
        self._curStep = -1 # first step is 0
        self._pool = pool
        # self._wd = wd
        self._te = None # prepare for every new step
        self._dbManager = dbManager
        self._executedTasks: List[Task] = [] # in a given step
        self._lock = threading.RLock() # sync access for a few things

        self._stepBarrier = threading.Barrier(self._pool.numThreads + 1) # one barrier for all threads
        self._execStats = ExecutionStats()
        self._runStatus = MainExec.STATUS_RUNNING

    def getTaskExecutor(self):
        return self._te

    def getDbManager(self) -> DbManager :
        return self._dbManager

    def crossStepBarrier(self):
        self._stepBarrier.wait()

    def requestToStop(self):
        self._runStatus = MainExec.STATUS_STOPPING
        self._execStats.registerFailure("User Interruption")

    def run(self):              
        self._pool.createAndStartThreads(self)

        # Coordinate all threads step by step
        self._curStep = -1 # not started yet
        maxSteps = gConfig.max_steps # type: ignore
        self._execStats.startExec() # start the stop watch
        transitionFailed = False
        hasAbortedTask = False
        while(self._curStep < maxSteps-1 and 
            (not transitionFailed) and 
            (self._runStatus==MainExec.STATUS_RUNNING) and
            (not hasAbortedTask)):  # maxStep==10, last curStep should be 9

            if not gConfig.debug: 
                print(".", end="", flush=True) # print this only if we are not in debug mode
            logger.debug("[TRD] Main thread going to sleep")

            # Now main thread (that's us) is ready to enter a step
            self.crossStepBarrier() # let other threads go past the pool barrier, but wait at the thread gate
            self._stepBarrier.reset() # Other worker threads should now be at the "gate"            

            # At this point, all threads should be pass the overall "barrier" and before the per-thread "gate"
            # We use this period to do house keeping work, when all worker threads are QUIET.
            hasAbortedTask = False
            for task in self._executedTasks :
                if task.isAborted() :
                    print("Task aborted: {}".format(task))
                    hasAbortedTask = True
                    break

            if hasAbortedTask : # do transition only if tasks are error free
                self._execStats.registerFailure("Aborted Task Encountered")
            else: 
                try:
                    sm = self._dbManager.getStateMachine()
                    logger.debug("[STT] starting transitions")
                    sm.transition(self._executedTasks) # at end of step, transiton the DB state
                    logger.debug("[STT] transition ended")
                    # Due to limitation (or maybe not) of the Python library, we cannot share connections across threads
                    if sm.hasDatabase() :
                        for t in self._pool.threadList:
                            logger.debug("[DB] use db for all worker threads")
                            t.useDb()
                            # t.execSql("use db") # main thread executing "use db" on behalf of every worker thread
                except taos.error.ProgrammingError as err:
                    if ( err.msg == 'network unavailable' ): # broken DB connection
                        logger.info("DB connection broken, execution failed")
                        traceback.print_stack()
                        transitionFailed = True
                        self._te = None # Not running any more
                        self._execStats.registerFailure("Broken DB Connection")
                        # continue # don't do that, need to tap all threads at end, and maybe signal them to stop
                    else:
                        raise 
            # finally:
            #     pass
            
            self.resetExecutedTasks() # clear the tasks after we are done

            # Get ready for next step
            logger.debug("<-- Step {} finished".format(self._curStep))
            self._curStep += 1 # we are about to get into next step. TODO: race condition here!                
            logger.debug("\r\n\n--> Step {} starts with main thread waking up".format(self._curStep)) # Now not all threads had time to go to sleep

            # A new TE for the new step
            if not transitionFailed: # only if not failed
                self._te = TaskExecutor(self._curStep)

            logger.debug("[TRD] Main thread waking up at step {}, tapping worker threads".format(self._curStep)) # Now not all threads had time to go to sleep            
            self.tapAllThreads() # Worker threads will wake up at this point, and each execute it's own task

        logger.debug("Main thread ready to finish up...")
        if not transitionFailed: # only in regular situations
            self.crossStepBarrier() # Cross it one last time, after all threads finish
            self._stepBarrier.reset()
            logger.debug("Main thread in exclusive zone...")
            self._te = None # No more executor, time to end
            logger.debug("Main thread tapping all threads one last time...")
            self.tapAllThreads() # Let the threads run one last time

        logger.debug("Main thread joining all threads")
        self._pool.joinAll() # Get all threads to finish
        logger.info("\nAll worker threads finished")
        self._execStats.endExec()

    def printStats(self):
        self._execStats.printStats()

    def isFailed(self):
        return self._execStats.isFailed()

    def getExecStats(self):
        return self._execStats

    def tapAllThreads(self): # in a deterministic manner
        wakeSeq = []
        for i in range(self._pool.numThreads): # generate a random sequence
            if Dice.throw(2) == 1 :
                wakeSeq.append(i)
            else:
                wakeSeq.insert(0, i)
        logger.debug("[TRD] Main thread waking up worker threads: {}".format(str(wakeSeq)))
        # TODO: set dice seed to a deterministic value
        for i in wakeSeq:
            self._pool.threadList[i].tapStepGate() # TODO: maybe a bit too deep?!
            time.sleep(0) # yield

    def isRunning(self):
        return self._te != None

    def fetchTask(self) -> Task :
        if ( not self.isRunning() ): # no task
            raise RuntimeError("Cannot fetch task when not running")
        # return self._wd.pickTask()
        # Alternatively, let's ask the DbState for the appropriate task
        # dbState = self.getDbState()
        # tasks = dbState.getTasksAtState() # TODO: create every time?
        # nTasks = len(tasks)
        # i = Dice.throw(nTasks)
        # logger.debug(" (dice:{}/{}) ".format(i, nTasks))
        # # return copy.copy(tasks[i]) # Needs a fresh copy, to save execution results, etc.
        # return tasks[i].clone() # TODO: still necessary?
        taskType = self.getDbManager().getStateMachine().pickTaskType() # pick a task type for current state
        return taskType(self.getDbManager(), self._execStats) # create a task from it

    def resetExecutedTasks(self):
        self._executedTasks = [] # should be under single thread

    def saveExecutedTask(self, task):
        with self._lock:
            self._executedTasks.append(task)

# We define a class to run a number of threads in locking steps.
class ThreadPool:
    def __init__(self, numThreads, maxSteps):
        self.numThreads = numThreads
        self.maxSteps = maxSteps
        # Internal class variables
        self.curStep = 0
        self.threadList = [] # type: List[WorkerThread]
        
    # starting to run all the threads, in locking steps
    def createAndStartThreads(self, tc: ThreadCoordinator):
        for tid in range(0, self.numThreads): # Create the threads
            workerThread = WorkerThread(self, tid, tc)            
            self.threadList.append(workerThread)
            workerThread.start() # start, but should block immediately before step 0

    def joinAll(self):
        for workerThread in self.threadList:
            logger.debug("Joining thread...")
            workerThread._thread.join()

# A queue of continguous POSITIVE integers, used by DbManager to generate continuous numbers
# for new table names
class LinearQueue():
    def __init__(self):
        self.firstIndex = 1  # 1st ever element
        self.lastIndex = 0
        self._lock = threading.RLock() # our functions may call each other
        self.inUse = set() # the indexes that are in use right now

    def toText(self):
        return "[{}..{}], in use: {}".format(self.firstIndex, self.lastIndex, self.inUse)

    # Push (add new element, largest) to the tail, and mark it in use
    def push(self): 
        with self._lock:
            # if ( self.isEmpty() ): 
            #     self.lastIndex = self.firstIndex 
            #     return self.firstIndex
            # Otherwise we have something
            self.lastIndex += 1
            self.allocate(self.lastIndex)
            # self.inUse.add(self.lastIndex) # mark it in use immediately
            return self.lastIndex

    def pop(self):
        with self._lock:
            if ( self.isEmpty() ): 
                # raise RuntimeError("Cannot pop an empty queue") 
                return False # TODO: None?
            
            index = self.firstIndex
            if ( index in self.inUse ):
                return False

            self.firstIndex += 1
            return index

    def isEmpty(self):
        return self.firstIndex > self.lastIndex

    def popIfNotEmpty(self):
        with self._lock:
            if (self.isEmpty()):
                return 0
            return self.pop()

    def allocate(self, i):
        with self._lock:
            # logger.debug("LQ allocating item {}".format(i))
            if ( i in self.inUse ):
                raise RuntimeError("Cannot re-use same index in queue: {}".format(i))
            self.inUse.add(i)

    def release(self, i):
        with self._lock:
            # logger.debug("LQ releasing item {}".format(i))
            self.inUse.remove(i) # KeyError possible, TODO: why?

    def size(self):
        return self.lastIndex + 1 - self.firstIndex

    def pickAndAllocate(self):
        if ( self.isEmpty() ):
            return None
        with self._lock:
            cnt = 0 # counting the interations
            while True:
                cnt += 1
                if ( cnt > self.size()*10 ): # 10x iteration already
                    # raise RuntimeError("Failed to allocate LinearQueue element")
                    return None
                ret = Dice.throwRange(self.firstIndex, self.lastIndex+1)
                if ( not ret in self.inUse ):
                    self.allocate(ret)
                    return ret

class DbConn:
    TYPE_NATIVE = "native-c"
    TYPE_REST = "rest-api"
    TYPE_INVALID = "invalid"

    @classmethod
    def create(cls, connType):
        if connType == cls.TYPE_NATIVE:
            return DbConnNative()
        elif connType == cls.TYPE_REST:
            return DbConnRest()
        else:
            raise RuntimeError("Unexpected connection type: {}".format(connType))

    @classmethod
    def createNative(cls):
        return cls.create(cls.TYPE_NATIVE)

    @classmethod
    def createRest(cls):
        return cls.create(cls.TYPE_REST)

    def __init__(self):
        self.isOpen = False
        self._type = self.TYPE_INVALID

    def open(self):
        if ( self.isOpen ):
            raise RuntimeError("Cannot re-open an existing DB connection")

        # below implemented by child classes
        self.openByType()

        logger.debug("[DB] data connection opened, type = {}".format(self._type))
        self.isOpen = True

    def resetDb(self): # reset the whole database, etc.
        if ( not self.isOpen ):
            raise RuntimeError("Cannot reset database until connection is open")
        # self._tdSql.prepare() # Recreate database, etc.

        self.execute('drop database if exists db')
        logger.debug("Resetting DB, dropped database")
        # self._cursor.execute('create database db')
        # self._cursor.execute('use db')
        # tdSql.execute('show databases')

    def queryScalar(self, sql) -> int :
        return self._queryAny(sql)

    def queryString(self, sql) -> str :
        return self._queryAny(sql)

    def _queryAny(self, sql) : # actual query result as an int
        if ( not self.isOpen ):
            raise RuntimeError("Cannot query database until connection is open")
        nRows = self.query(sql)
        if nRows != 1 :
            raise RuntimeError("Unexpected result for query: {}, rows = {}".format(sql, nRows))
        if self.getResultRows() != 1 or self.getResultCols() != 1:
            raise RuntimeError("Unexpected result set for query: {}".format(sql))
        return self.getQueryResult()[0][0]

    def execute(self, sql):
        raise RuntimeError("Unexpected execution, should be overriden")
    def openByType(self):
        raise RuntimeError("Unexpected execution, should be overriden")
    def getQueryResult(self):
        raise RuntimeError("Unexpected execution, should be overriden")
    def getResultRows(self):
        raise RuntimeError("Unexpected execution, should be overriden")
    def getResultCols(self):
        raise RuntimeError("Unexpected execution, should be overriden")

# Sample: curl -u root:taosdata -d "show databases" localhost:6020/rest/sql
class DbConnRest(DbConn):
    def __init__(self):
        super().__init__()
        self._type = self.TYPE_REST
        self._url = "http://localhost:6020/rest/sql" # fixed for now
        self._result = None

    def openByType(self): # Open connection
        pass # do nothing, always open
        
    def close(self):
        if ( not self.isOpen ):
            raise RuntimeError("Cannot clean up database until connection is open")
        # Do nothing for REST
        logger.debug("[DB] REST Database connection closed")
        self.isOpen = False

    def _doSql(self, sql):
        r = requests.post(self._url, 
            data = sql,
            auth = HTTPBasicAuth('root', 'taosdata'))
        rj = r.json()
        # Sanity check for the "Json Result"
        if (not 'status' in rj):
            raise RuntimeError("No status in REST response")

        if rj['status'] == 'error': # clearly reported error
            if (not 'code' in rj): # error without code
                raise RuntimeError("REST error return without code")            
            errno = rj['code'] # May need to massage this in the future
            # print("Raising programming error with REST return: {}".format(rj))
            raise taos.error.ProgrammingError(rj['desc'], errno) # todo: check existance of 'desc'

        if rj['status'] != 'succ': # better be this
            raise RuntimeError("Unexpected REST return status: {}".format(rj['status']))

        nRows = rj['rows'] if ('rows' in rj) else 0
        self._result = rj        
        return nRows

    def execute(self, sql): 
        if ( not self.isOpen ):
            raise RuntimeError("Cannot execute database commands until connection is open")
        logger.debug("[SQL-REST] Executing SQL: {}".format(sql))
        nRows = self._doSql(sql)
        logger.debug("[SQL-REST] Execution Result, nRows = {}, SQL = {}".format(nRows, sql))
        return nRows

    def query(self, sql) :  # return rows affected
        return self.execute(sql)

    def getQueryResult(self):
        return self._result['data']

    def getResultRows(self):
        print(self._result)
        raise RuntimeError("TBD")
        # return self._tdSql.queryRows

    def getResultCols(self):
        print(self._result)
        raise RuntimeError("TBD")
    
class DbConnNative(DbConn):
    def __init__(self):
        super().__init__()
        self._type = self.TYPE_REST
        self._conn = None 
        self._cursor = None
        
    def openByType(self): # Open connection
        cfgPath = "../../build/test/cfg" 
        self._conn = taos.connect(host="127.0.0.1", config=cfgPath) # TODO: make configurable
        self._cursor = self._conn.cursor()

        # Get the connection/cursor ready
        self._cursor.execute('reset query cache')
        # self._cursor.execute('use db') # do this at the beginning of every step

        # Open connection
        self._tdSql = TDSql()
        self._tdSql.init(self._cursor)
        
    def close(self):
        if ( not self.isOpen ):
            raise RuntimeError("Cannot clean up database until connection is open")
        self._tdSql.close()
        logger.debug("[DB] Database connection closed")
        self.isOpen = False

    def execute(self, sql): 
        if ( not self.isOpen ):
            raise RuntimeError("Cannot execute database commands until connection is open")
        logger.debug("[SQL] Executing SQL: {}".format(sql))
        nRows = self._tdSql.execute(sql)
        logger.debug("[SQL] Execution Result, nRows = {}, SQL = {}".format(nRows, sql))
        return nRows

    def query(self, sql) :  # return rows affected
        if ( not self.isOpen ):
            raise RuntimeError("Cannot query database until connection is open")
        logger.debug("[SQL] Executing SQL: {}".format(sql))
        nRows = self._tdSql.query(sql)
        logger.debug("[SQL] Query Result, nRows = {}, SQL = {}".format(nRows, sql))
        return nRows
        # results are in: return self._tdSql.queryResult

    def getQueryResult(self):
        return self._tdSql.queryResult

    def getResultRows(self):
        return self._tdSql.queryRows

    def getResultCols(self):
        return self._tdSql.queryCols

    
class AnyState:
    STATE_INVALID    = -1
    STATE_EMPTY      = 0  # nothing there, no even a DB
    STATE_DB_ONLY    = 1  # we have a DB, but nothing else
    STATE_TABLE_ONLY = 2  # we have a table, but totally empty
    STATE_HAS_DATA   = 3  # we have some data in the table
    _stateNames = ["Invalid", "Empty", "DB_Only", "Table_Only", "Has_Data"]

    STATE_VAL_IDX = 0
    CAN_CREATE_DB = 1
    CAN_DROP_DB = 2
    CAN_CREATE_FIXED_SUPER_TABLE = 3
    CAN_DROP_FIXED_SUPER_TABLE = 4
    CAN_ADD_DATA = 5
    CAN_READ_DATA = 6

    def __init__(self):
        self._info = self.getInfo()

    def __str__(self):
        return self._stateNames[self._info[self.STATE_VAL_IDX] + 1] # -1 hack to accomodate the STATE_INVALID case

    def getInfo(self):
        raise RuntimeError("Must be overriden by child classes")

    def equals(self, other):
        if isinstance(other, int):
            return self.getValIndex() == other
        elif isinstance(other, AnyState):
            return self.getValIndex() == other.getValIndex()
        else:
            raise RuntimeError("Unexpected comparison, type = {}".format(type(other)))

    def verifyTasksToState(self, tasks, newState):
        raise RuntimeError("Must be overriden by child classes")

    def getValIndex(self):
        return self._info[self.STATE_VAL_IDX]

    def getValue(self):
        return self._info[self.STATE_VAL_IDX]
    def canCreateDb(self):
        return self._info[self.CAN_CREATE_DB]
    def canDropDb(self):
        return self._info[self.CAN_DROP_DB]
    def canCreateFixedSuperTable(self):
        return self._info[self.CAN_CREATE_FIXED_SUPER_TABLE]
    def canDropFixedSuperTable(self):
        return self._info[self.CAN_DROP_FIXED_SUPER_TABLE]
    def canAddData(self):
        return self._info[self.CAN_ADD_DATA]
    def canReadData(self):
        return self._info[self.CAN_READ_DATA]

    def assertAtMostOneSuccess(self, tasks, cls):
        sCnt = 0
        for task in tasks :
            if not isinstance(task, cls):
                continue
            if task.isSuccess():
                # task.logDebug("Task success found")
                sCnt += 1
                if ( sCnt >= 2 ):
                    raise RuntimeError("Unexpected more than 1 success with task: {}".format(cls))

    def assertIfExistThenSuccess(self, tasks, cls):
        sCnt = 0
        exists = False
        for task in tasks :
            if not isinstance(task, cls):
                continue
            exists = True # we have a valid instance
            if task.isSuccess():
                sCnt += 1
        if ( exists and sCnt <= 0 ):
            raise RuntimeError("Unexpected zero success for task: {}".format(cls))

    def assertNoTask(self, tasks, cls):
        for task in tasks :
            if isinstance(task, cls):
                raise CrashGenError("This task: {}, is not expected to be present, given the success/failure of others".format(cls.__name__))

    def assertNoSuccess(self, tasks, cls):
        for task in tasks :
            if isinstance(task, cls):
                if task.isSuccess():
                    raise RuntimeError("Unexpected successful task: {}".format(cls))

    def hasSuccess(self, tasks, cls):
        for task in tasks :
            if not isinstance(task, cls):
                continue
            if task.isSuccess():
                return True
        return False

    def hasTask(self, tasks, cls):
        for task in tasks :
            if isinstance(task, cls):
                return True
        return False

class StateInvalid(AnyState):
    def getInfo(self):
        return [
            self.STATE_INVALID,
            False, False, # can create/drop Db
            False, False, # can create/drop fixed table
            False, False, # can insert/read data with fixed table
        ]

    # def verifyTasksToState(self, tasks, newState):

class StateEmpty(AnyState):
    def getInfo(self):
        return [
            self.STATE_EMPTY,
            True, False, # can create/drop Db
            False, False, # can create/drop fixed table
            False, False, # can insert/read data with fixed table
        ]

    def verifyTasksToState(self, tasks, newState): 
        if ( self.hasSuccess(tasks, TaskCreateDb) ): # at EMPTY, if there's succes in creating DB
            if ( not self.hasTask(tasks, TaskDropDb) ) : # and no drop_db tasks
                self.assertAtMostOneSuccess(tasks, TaskCreateDb) # we must have at most one. TODO: compare numbers

class StateDbOnly(AnyState):
    def getInfo(self):
        return [
            self.STATE_DB_ONLY,
            False, True,
            True, False,
            False, False,
        ]

    def verifyTasksToState(self, tasks, newState):
        if ( not self.hasTask(tasks, TaskCreateDb) ):
            self.assertAtMostOneSuccess(tasks, TaskDropDb) # only if we don't create any more
        self.assertIfExistThenSuccess(tasks, TaskDropDb)
        # self.assertAtMostOneSuccess(tasks, CreateFixedTableTask) # not true in massively parrallel cases
        # Nothing to be said about adding data task
        # if ( self.hasSuccess(tasks, DropDbTask) ): # dropped the DB
            # self.assertHasTask(tasks, DropDbTask) # implied by hasSuccess
            # self.assertAtMostOneSuccess(tasks, DropDbTask)
            # self._state = self.STATE_EMPTY
        # if ( self.hasSuccess(tasks, TaskCreateSuperTable) ): # did not drop db, create table success
        #     # self.assertHasTask(tasks, CreateFixedTableTask) # tried to create table
        #     if ( not self.hasTask(tasks, TaskDropSuperTable) ): 
        #         self.assertAtMostOneSuccess(tasks, TaskCreateSuperTable) # at most 1 attempt is successful, if we don't drop anything
            # self.assertNoTask(tasks, DropDbTask) # should have have tried
            # if ( not self.hasSuccess(tasks, AddFixedDataTask) ): # just created table, no data yet
            #     # can't say there's add-data attempts, since they may all fail
            #     self._state = self.STATE_TABLE_ONLY
            # else:                    
            #     self._state = self.STATE_HAS_DATA
        # What about AddFixedData?
        # elif ( self.hasSuccess(tasks, AddFixedDataTask) ):
        #     self._state = self.STATE_HAS_DATA
        # else: # no success in dropping db tasks, no success in create fixed table? read data should also fail
        #     # raise RuntimeError("Unexpected no-success scenario")   # We might just landed all failure tasks, 
        #     self._state = self.STATE_DB_ONLY  # no change

class StateSuperTableOnly(AnyState):
    def getInfo(self):
        return [
            self.STATE_TABLE_ONLY,
            False, True,
            False, True,
            True, True,
        ]

    def verifyTasksToState(self, tasks, newState):
        if ( self.hasSuccess(tasks, TaskDropSuperTable) ): # we are able to drop the table
            #self.assertAtMostOneSuccess(tasks, TaskDropSuperTable)
            self.hasSuccess(tasks, TaskCreateSuperTable) # we must have had recreted it

            # self._state = self.STATE_DB_ONLY
        # elif ( self.hasSuccess(tasks, AddFixedDataTask) ): # no success dropping the table, but added data
        #     self.assertNoTask(tasks, DropFixedTableTask) # not true in massively parrallel cases
            # self._state = self.STATE_HAS_DATA
        # elif ( self.hasSuccess(tasks, ReadFixedDataTask) ): # no success in prev cases, but was able to read data
            # self.assertNoTask(tasks, DropFixedTableTask)
            # self.assertNoTask(tasks, AddFixedDataTask)
            # self._state = self.STATE_TABLE_ONLY # no change
        # else: # did not drop table, did not insert data, did not read successfully, that is impossible
        #     raise RuntimeError("Unexpected no-success scenarios")
        # TODO: need to revamp!!

class StateHasData(AnyState):
    def getInfo(self):
        return [
            self.STATE_HAS_DATA,
            False, True,
            False, True,
            True, True,
        ]

    def verifyTasksToState(self, tasks, newState):
        if ( newState.equals(AnyState.STATE_EMPTY) ):
            self.hasSuccess(tasks, TaskDropDb)
            if ( not self.hasTask(tasks, TaskCreateDb) ) : 
                self.assertAtMostOneSuccess(tasks, TaskDropDb) # TODO: dicy
        elif ( newState.equals(AnyState.STATE_DB_ONLY) ): # in DB only
            if ( not self.hasTask(tasks, TaskCreateDb)): # without a create_db task
                self.assertNoTask(tasks, TaskDropDb) # we must have drop_db task
            self.hasSuccess(tasks, TaskDropSuperTable)
            # self.assertAtMostOneSuccess(tasks, DropFixedSuperTableTask) # TODO: dicy
        # elif ( newState.equals(AnyState.STATE_TABLE_ONLY) ): # data deleted
            # self.assertNoTask(tasks, TaskDropDb)
            # self.assertNoTask(tasks, TaskDropSuperTable)
            # self.assertNoTask(tasks, TaskAddData)
            # self.hasSuccess(tasks, DeleteDataTasks)
        else: # should be STATE_HAS_DATA
            if (not self.hasTask(tasks, TaskCreateDb) ): # only if we didn't create one
                self.assertNoTask(tasks, TaskDropDb) # we shouldn't have dropped it
            if (not self.hasTask(tasks, TaskCreateSuperTable)) :  # if we didn't create the table
                self.assertNoTask(tasks, TaskDropSuperTable) # we should not have a task that drops it            
            # self.assertIfExistThenSuccess(tasks, ReadFixedDataTask)

class StateMechine:
    def __init__(self, dbConn):
        self._dbConn = dbConn
        self._curState = self._findCurrentState() # starting state
        self._stateWeights = [1,3,5,15] # transitition target probabilities, indexed with value of STATE_EMPTY, STATE_DB_ONLY, etc.
        
    def getCurrentState(self):
        return self._curState

    def hasDatabase(self):
        return self._curState.canDropDb()  # ha, can drop DB means it has one

    # May be slow, use cautionsly...
    def getTaskTypes(self): # those that can run (directly/indirectly) from the current state
        def typesToStrings(types):
            ss = []
            for t in types:
                ss.append(t.__name__)
            return ss

        allTaskClasses = StateTransitionTask.__subclasses__() # all state transition tasks
        firstTaskTypes = []
        for tc in allTaskClasses:
            # t = tc(self) # create task object            
            if tc.canBeginFrom(self._curState):
                firstTaskTypes.append(tc)
        # now we have all the tasks that can begin directly from the current state, let's figure out the INDIRECT ones
        taskTypes = firstTaskTypes.copy() # have to have these
        for task1 in firstTaskTypes: # each task type gathered so far
            endState = task1.getEndState() # figure the end state
            if endState == None: # does not change end state
                continue # no use, do nothing
            for tc in allTaskClasses: # what task can further begin from there?
                if tc.canBeginFrom(endState) and (tc not in firstTaskTypes):
                    taskTypes.append(tc) # gather it

        if len(taskTypes) <= 0:
            raise RuntimeError("No suitable task types found for state: {}".format(self._curState))   
        logger.debug("[OPS] Tasks found for state {}: {}".format(self._curState, typesToStrings(taskTypes)))     
        return taskTypes

    def _findCurrentState(self):
        dbc = self._dbConn
        ts = time.time() # we use this to debug how fast/slow it is to do the various queries to find the current DB state
        if dbc.query("show databases") == 0 : # no database?!
            # logger.debug("Found EMPTY state")
            logger.debug("[STT] empty database found, between {} and {}".format(ts, time.time()))
            return StateEmpty()
        dbc.execute("use db") # did not do this when openning connection, and this is NOT the worker thread, which does this on their own
        if dbc.query("show tables") == 0 : # no tables
            # logger.debug("Found DB ONLY state")
            logger.debug("[STT] DB_ONLY found, between {} and {}".format(ts, time.time()))
            return StateDbOnly()
        if dbc.query("SELECT * FROM db.{}".format(DbManager.getFixedSuperTableName()) ) == 0 : # no regular tables
            # logger.debug("Found TABLE_ONLY state")
            logger.debug("[STT] SUPER_TABLE_ONLY found, between {} and {}".format(ts, time.time()))
            return StateSuperTableOnly()
        else: # has actual tables
            # logger.debug("Found HAS_DATA state")
            logger.debug("[STT] HAS_DATA found, between {} and {}".format(ts, time.time()))
            return StateHasData()

    def transition(self, tasks):
        if ( len(tasks) == 0 ): # before 1st step, or otherwise empty
            logger.debug("[STT] Starting State: {}".format(self._curState))
            return # do nothing

        self._dbConn.execute("show dnodes") # this should show up in the server log, separating steps

        # Generic Checks, first based on the start state
        if self._curState.canCreateDb():
            self._curState.assertIfExistThenSuccess(tasks, TaskCreateDb)
            # self.assertAtMostOneSuccess(tasks, CreateDbTask) # not really, in case of multiple creation and drops

        if self._curState.canDropDb():
            self._curState.assertIfExistThenSuccess(tasks, TaskDropDb)
            # self.assertAtMostOneSuccess(tasks, DropDbTask) # not really in case of drop-create-drop

        # if self._state.canCreateFixedTable():
            # self.assertIfExistThenSuccess(tasks, CreateFixedTableTask) # Not true, DB may be dropped
            # self.assertAtMostOneSuccess(tasks, CreateFixedTableTask) # not really, in case of create-drop-create

        # if self._state.canDropFixedTable():
            # self.assertIfExistThenSuccess(tasks, DropFixedTableTask) # Not True, the whole DB may be dropped
            # self.assertAtMostOneSuccess(tasks, DropFixedTableTask) # not really in case of drop-create-drop

        # if self._state.canAddData():
        #     self.assertIfExistThenSuccess(tasks, AddFixedDataTask)  # not true actually

        # if self._state.canReadData():
            # Nothing for sure

        newState = self._findCurrentState()
        logger.debug("[STT] New DB state determined: {}".format(newState))
        self._curState.verifyTasksToState(tasks, newState) # can old state move to new state through the tasks?
        self._curState = newState

    def pickTaskType(self):
        taskTypes = self.getTaskTypes() # all the task types we can choose from at curent state
        weights = []
        for tt in taskTypes:
            endState = tt.getEndState()
            if endState != None :
                weights.append(self._stateWeights[endState.getValIndex()]) # TODO: change to a method
            else:
                weights.append(10) # read data task, default to 10: TODO: change to a constant
        i = self._weighted_choice_sub(weights)
        # logger.debug(" (weighted random:{}/{}) ".format(i, len(taskTypes)))        
        return taskTypes[i]

    def _weighted_choice_sub(self, weights): # ref: https://eli.thegreenplace.net/2010/01/22/weighted-random-generation-in-python/
        rnd = random.random() * sum(weights) # TODO: use our dice to ensure it being determinstic?
        for i, w in enumerate(weights):
            rnd -= w
            if rnd < 0:
                return i

# Manager of the Database Data/Connection
class DbManager():    
    def __init__(self, resetDb = True):
        self.tableNumQueue = LinearQueue()
        self._lastTick = self.setupLastTick() # datetime.datetime(2019, 1, 1) # initial date time tick
        self._lastInt  = 0 # next one is initial integer 
        self._lock = threading.RLock()
        
        # self.openDbServerConnection()
        self._dbConn = DbConn.createNative() if (gConfig.connector_type=='native') else DbConn.createRest()
        try:
            self._dbConn.open() # may throw taos.error.ProgrammingError: disconnected
        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
                print("Cannot establish DB connection, please re-run script without parameter, and follow the instructions.")
                sys.exit(2)
            else:
                raise            
        except:
            print("[=] Unexpected exception")
            raise        

        if resetDb :
            self._dbConn.resetDb() # drop and recreate DB            

        self._stateMachine = StateMechine(self._dbConn) # Do this after dbConn is in proper shape
        
    def getDbConn(self):
        return self._dbConn

    def getStateMachine(self) -> StateMechine :
        return self._stateMachine

    # def getState(self):
    #     return self._stateMachine.getCurrentState()

    # We aim to create a starting time tick, such that, whenever we run our test here once
    # We should be able to safely create 100,000 records, which will not have any repeated time stamp
    # when we re-run the test in 3 minutes (180 seconds), basically we should expand time duration
    # by a factor of 500.
    # TODO: what if it goes beyond 10 years into the future
    # TODO: fix the error as result of above: "tsdb timestamp is out of range"
    def setupLastTick(self):
        t1 = datetime.datetime(2020, 6, 1)
        t2 = datetime.datetime.now()
        elSec = int(t2.timestamp() - t1.timestamp()) # maybe a very large number, takes 69 years to exceed Python int range
        elSec2 = (  elSec % (8 * 12 * 30 * 24 * 60 * 60 / 500 ) ) * 500 # a number representing seconds within 10 years
        # print("elSec = {}".format(elSec))
        t3 = datetime.datetime(2012, 1, 1) # default "keep" is 10 years
        t4 = datetime.datetime.fromtimestamp( t3.timestamp() + elSec2) # see explanation above
        logger.info("Setting up TICKS to start from: {}".format(t4))
        return t4

    def pickAndAllocateTable(self): # pick any table, and "use" it
        return self.tableNumQueue.pickAndAllocate()

    def addTable(self):
        with self._lock:
            tIndex = self.tableNumQueue.push()
        return tIndex

    @classmethod
    def getFixedSuperTableName(cls):
        return "fs_table"

    def releaseTable(self, i): # return the table back, so others can use it
        self.tableNumQueue.release(i)

    def getNextTick(self):
        with self._lock: # prevent duplicate tick
            if Dice.throw(10) == 0 : # 1 in 10 chance
                return self._lastTick + datetime.timedelta(0, -100)
            else: # regular
                self._lastTick += datetime.timedelta(0, 1) # add one second to it
                return self._lastTick

    def getNextInt(self):
        with self._lock:
            self._lastInt += 1
            return self._lastInt

    def getNextBinary(self):
        return "Beijing_Shanghai_Los_Angeles_New_York_San_Francisco_Chicago_Beijing_Shanghai_Los_Angeles_New_York_San_Francisco_Chicago_{}".format(self.getNextInt())

    def getNextFloat(self):
        return 0.9 + self.getNextInt()
    
    def getTableNameToDelete(self):
        tblNum = self.tableNumQueue.pop() # TODO: race condition!
        if ( not tblNum ): # maybe false
            return False
        
        return "table_{}".format(tblNum)

    def cleanUp(self):
        self._dbConn.close()      

class TaskExecutor():
    class BoundedList:
        def __init__(self, size = 10):
            self._size = size
            self._list = []

        def add(self, n: int) :
            if not self._list: # empty
                self._list.append(n)
                return
            # now we should insert
            nItems = len(self._list)
            insPos = 0
            for i in range(nItems):
                insPos = i
                if n <= self._list[i] : # smaller than this item, time to insert
                    break # found the insertion point
                insPos += 1 # insert to the right

            if insPos == 0 : # except for the 1st item, # TODO: elimiate first item as gating item
                return # do nothing

            # print("Inserting at postion {}, value: {}".format(insPos, n))
            self._list.insert(insPos, n) # insert
            
            newLen = len(self._list)
            if newLen <= self._size :
                return # do nothing
            elif newLen == (self._size + 1) :                
                del self._list[0] # remove the first item
            else :
                raise RuntimeError("Corrupt Bounded List")

        def __str__(self):
            return repr(self._list)

    _boundedList = BoundedList()

    def __init__(self, curStep):
        self._curStep = curStep

    @classmethod
    def getBoundedList(cls):
        return cls._boundedList

    def getCurStep(self):
        return self._curStep

    def execute(self, task: Task, wt: WorkerThread): # execute a task on a thread
        task.execute(wt)

    def recordDataMark(self, n: int):
        # print("[{}]".format(n), end="", flush=True)
        self._boundedList.add(n)

    # def logInfo(self, msg):
    #     logger.info("    T[{}.x]: ".format(self._curStep) + msg)

    # def logDebug(self, msg):
    #     logger.debug("    T[{}.x]: ".format(self._curStep) + msg)

class Task():
    taskSn = 100

    @classmethod
    def allocTaskNum(cls):
        Task.taskSn += 1 # IMPORTANT: cannot use cls.taskSn, since each sub class will have a copy
        # logger.debug("Allocating taskSN: {}".format(Task.taskSn))
        return Task.taskSn

    def __init__(self, dbManager: DbManager, execStats: ExecutionStats):        
        self._dbManager = dbManager
        self._workerThread = None 
        self._err = None
        self._aborted = False
        self._curStep = None
        self._numRows = None # Number of rows affected

        # Assign an incremental task serial number        
        self._taskNum = self.allocTaskNum()
        # logger.debug("Creating new task {}...".format(self._taskNum))

        self._execStats = execStats
        self._lastSql = "" # last SQL executed/attempted

    def isSuccess(self):
        return self._err == None

    def isAborted(self):
        return self._aborted

    def clone(self): # TODO: why do we need this again?
        newTask = self.__class__(self._dbManager, self._execStats)
        return newTask

    def logDebug(self, msg):
        self._workerThread.logDebug("Step[{}.{}] {}".format(self._curStep, self._taskNum, msg))

    def logInfo(self, msg):
        self._workerThread.logInfo("Step[{}.{}] {}".format(self._curStep, self._taskNum, msg))

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        raise RuntimeError("To be implemeted by child classes, class name: {}".format(self.__class__.__name__))

    def execute(self, wt: WorkerThread):
        wt.verifyThreadSelf()
        self._workerThread = wt # type: ignore

        te = wt.getTaskExecutor()
        self._curStep = te.getCurStep()
        self.logDebug("[-] executing task {}...".format(self.__class__.__name__))

        self._err = None
        self._execStats.beginTaskType(self.__class__.__name__) # mark beginning
        try:
            self._executeInternal(te, wt) # TODO: no return value?
        except taos.error.ProgrammingError as err:
            errno2 = err.errno if (err.errno > 0) else 0x80000000 + err.errno # correct error scheme
            if ( errno2 in [
                0x05, # TSDB_CODE_RPC_NOT_READY
                0x200, 0x360, 0x362, 0x36A, 0x36B, 0x36D, 0x381, 0x380, 0x383, 0x503, 
                0x510, # vnode not in ready state
                0x600,
                1000 # REST catch-all error
                ]) : # allowed errors
                self.logDebug("[=] Acceptable Taos library exception: errno=0x{:X}, msg: {}, SQL: {}".format(errno2, err, self._lastSql))
                print("_", end="", flush=True)
                self._err = err  
            else:
                errMsg = "[=] Unexpected Taos library exception: errno=0x{:X}, msg: {}, SQL: {}".format(errno2, err, self._lastSql)
                self.logDebug(errMsg)
                if gConfig.debug :
                    # raise # so that we see full stack
                    traceback.print_exc()
                print("\n\n----------------------------\nProgram ABORTED Due to Unexpected TAOS Error: \n\n{}\n".format(errMsg) +
                    "----------------------------\n")
                # sys.exit(-1)
                self._err = err
                self._aborted = True
        except Exception as e :
            self.logInfo("Non-TAOS exception encountered")
            self._err = e 
            self._aborted = True
            traceback.print_exc()
        except BaseException as e :
            self.logInfo("Python base exception encountered")
            self._err = e 
            self._aborted = True
            traceback.print_exc()
        except :
            self.logDebug("[=] Unexpected exception, SQL: {}".format(self._lastSql))
            raise
        self._execStats.endTaskType(self.__class__.__name__, self.isSuccess())
        
        self.logDebug("[X] task execution completed, {}, status: {}".format(self.__class__.__name__, "Success" if self.isSuccess() else "Failure"))        
        self._execStats.incExecCount(self.__class__.__name__, self.isSuccess()) # TODO: merge with above.

    def execSql(self, sql):
        self._lastSql = sql
        return self._dbManager.execute(sql)

    def execWtSql(self, wt: WorkerThread, sql): # execute an SQL on the worker thread
        self._lastSql = sql
        return wt.execSql(sql)

    def queryWtSql(self, wt: WorkerThread, sql): # execute an SQL on the worker thread
        self._lastSql = sql
        return wt.querySql(sql)

    def getQueryResult(self, wt: WorkerThread): # execute an SQL on the worker thread
        return wt.getQueryResult()


                  
class ExecutionStats:
    def __init__(self):
        self._execTimes: Dict[str, [int, int]] = {} # total/success times for a task
        self._tasksInProgress = 0
        self._lock = threading.Lock()
        self._firstTaskStartTime = None
        self._execStartTime = None
        self._elapsedTime = 0.0 # total elapsed time
        self._accRunTime = 0.0 # accumulated run time

        self._failed = False
        self._failureReason = None

    def __str__(self):
        return "[ExecStats: _failed={}, _failureReason={}".format(self._failed, self._failureReason)

    def isFailed(self):
        return self._failed == True

    def startExec(self):
        self._execStartTime = time.time()

    def endExec(self):
        self._elapsedTime = time.time() - self._execStartTime

    def incExecCount(self, klassName, isSuccess): # TODO: add a lock here
        if klassName not in self._execTimes:
            self._execTimes[klassName] = [0, 0]
        t = self._execTimes[klassName] # tuple for the data
        t[0] += 1 # index 0 has the "total" execution times
        if isSuccess:
            t[1] += 1 # index 1 has the "success" execution times

    def beginTaskType(self, klassName):
        with self._lock:
            if self._tasksInProgress == 0 : # starting a new round
                self._firstTaskStartTime = time.time() # I am now the first task
            self._tasksInProgress += 1

    def endTaskType(self, klassName, isSuccess):
        with self._lock:
            self._tasksInProgress -= 1
            if self._tasksInProgress == 0 : # all tasks have stopped
                self._accRunTime += (time.time() - self._firstTaskStartTime)
                self._firstTaskStartTime = None

    def registerFailure(self, reason):
        self._failed = True
        self._failureReason = reason

    def printStats(self):
        logger.info("----------------------------------------------------------------------")
        logger.info("| Crash_Gen test {}, with the following stats:".
            format("FAILED (reason: {})".format(self._failureReason) if self._failed else "SUCCEEDED"))
        logger.info("| Task Execution Times (success/total):")
        execTimesAny = 0
        for k, n in self._execTimes.items():            
            execTimesAny += n[0]
            logger.info("|    {0:<24}: {1}/{2}".format(k,n[1],n[0]))
                
        logger.info("| Total Tasks Executed (success or not): {} ".format(execTimesAny))
        logger.info("| Total Tasks In Progress at End: {}".format(self._tasksInProgress))
        logger.info("| Total Task Busy Time (elapsed time when any task is in progress): {:.3f} seconds".format(self._accRunTime))
        logger.info("| Average Per-Task Execution Time: {:.3f} seconds".format(self._accRunTime/execTimesAny))
        logger.info("| Total Elapsed Time (from wall clock): {:.3f} seconds".format(self._elapsedTime))
        logger.info("| Top numbers written: {}".format(TaskExecutor.getBoundedList()))
        logger.info("----------------------------------------------------------------------")
        


class StateTransitionTask(Task):
    LARGE_NUMBER_OF_TABLES = 35
    SMALL_NUMBER_OF_TABLES = 3
    LARGE_NUMBER_OF_RECORDS = 50
    SMALL_NUMBER_OF_RECORDS = 3

    @classmethod
    def getInfo(cls): # each sub class should supply their own information
        raise RuntimeError("Overriding method expected")

    _endState = None 
    @classmethod
    def getEndState(cls): # TODO: optimize by calling it fewer times
        raise RuntimeError("Overriding method expected")

    # @classmethod
    # def getBeginStates(cls):
    #     return cls.getInfo()[0]

    # @classmethod
    # def getEndState(cls): # returning the class name
    #     return cls.getInfo()[0]

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        # return state.getValue() in cls.getBeginStates()
        raise RuntimeError("must be overriden")

    @classmethod
    def getRegTableName(cls, i):
        return "db.reg_table_{}".format(i)

    def execute(self, wt: WorkerThread):
        super().execute(wt)
        
class TaskCreateDb(StateTransitionTask):
    @classmethod
    def getEndState(cls):
        return StateDbOnly() 

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canCreateDb()

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        self.execWtSql(wt, "create database db")       

class TaskDropDb(StateTransitionTask):
    @classmethod
    def getEndState(cls):
        return StateEmpty()

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canDropDb()

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        self.execWtSql(wt, "drop database db")
        logger.debug("[OPS] database dropped at {}".format(time.time()))

class TaskCreateSuperTable(StateTransitionTask):
    @classmethod
    def getEndState(cls):
        return StateSuperTableOnly()

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canCreateFixedSuperTable()

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        if not wt.dbInUse(): # no DB yet, to the best of our knowledge
            logger.debug("Skipping task, no DB yet")
            return

        tblName = self._dbManager.getFixedSuperTableName()   
        # wt.execSql("use db")    # should always be in place
        self.execWtSql(wt, "create table db.{} (ts timestamp, speed int) tags (b binary(200), f float) ".format(tblName))
        # No need to create the regular tables, INSERT will do that automatically


class TaskReadData(StateTransitionTask):
    @classmethod
    def getEndState(cls):
        return None # meaning doesn't affect state

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canReadData()

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        sTbName = self._dbManager.getFixedSuperTableName()        
        self.queryWtSql(wt, "select TBNAME from db.{}".format(sTbName)) # TODO: analyze result set later

        if random.randrange(5) == 0 : # 1 in 5 chance, simulate a broken connection. TODO: break connection in all situations
            wt.getDbConn().close()
            wt.getDbConn().open()
        else:
            rTables = self.getQueryResult(wt) # wt.getDbConn().getQueryResult()
            # print("rTables[0] = {}, type = {}".format(rTables[0], type(rTables[0])))
            for rTbName in rTables : # regular tables
                self.execWtSql(wt, "select * from db.{}".format(rTbName[0]))

        # tdSql.query(" cars where tbname in ('carzero', 'carone')")

class TaskDropSuperTable(StateTransitionTask):
    @classmethod
    def getEndState(cls):
        return StateDbOnly() 

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canDropFixedSuperTable()

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        # 1/2 chance, we'll drop the regular tables one by one, in a randomized sequence
        if Dice.throw(2) == 0 : 
            tblSeq = list(range(2 + (self.LARGE_NUMBER_OF_TABLES if gConfig.larger_data else self.SMALL_NUMBER_OF_TABLES))) 
            random.shuffle(tblSeq) 
            tickOutput = False # if we have spitted out a "d" character for "drop regular table"
            isSuccess = True
            for i in tblSeq: 
                regTableName = self.getRegTableName(i); # "db.reg_table_{}".format(i)                  
                try:
                    self.execWtSql(wt, "drop table {}".format(regTableName)) # nRows always 0, like MySQL
                except taos.error.ProgrammingError as err:                    
                    errno2 = err.errno if (err.errno > 0) else 0x80000000 + err.errno # correcting for strange error number scheme
                    if ( errno2 in [0x362]) : # mnode invalid table name
                        isSuccess = False
                        logger.debug("[DB] Acceptable error when dropping a table")
                    continue # try to delete next regular table

                if (not tickOutput):
                    tickOutput = True # Print only one time
                    if isSuccess :
                        print("d", end="", flush=True)
                    else:
                        print("f", end="", flush=True)                    

        # Drop the super table itself
        tblName = self._dbManager.getFixedSuperTableName()     
        self.execWtSql(wt, "drop table db.{}".format(tblName))

class TaskAlterTags(StateTransitionTask):
    @classmethod
    def getEndState(cls):
        return None # meaning doesn't affect state

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canDropFixedSuperTable() # if we can drop it, we can alter tags

    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        tblName = self._dbManager.getFixedSuperTableName()   
        dice = Dice.throw(4)
        if dice == 0 :
            sql = "alter table db.{} add tag extraTag int".format(tblName)
        elif dice == 1 :
            sql = "alter table db.{} drop tag extraTag".format(tblName)
        elif dice == 2 :
            sql = "alter table db.{} drop tag newTag".format(tblName)
        else: # dice == 3
            sql = "alter table db.{} change tag extraTag newTag".format(tblName)

        self.execWtSql(wt, sql)

class TaskAddData(StateTransitionTask):
    activeTable : Set[int] = set() # Track which table is being actively worked on

    # We use these two files to record operations to DB, useful for power-off tests
    fAddLogReady = None
    fAddLogDone = None

    @classmethod
    def prepToRecordOps(cls):
        if gConfig.record_ops :            
            if ( cls.fAddLogReady == None ):
                logger.info("Recording in a file operations to be performed...")
                cls.fAddLogReady = open("add_log_ready.txt", "w")
            if ( cls.fAddLogDone == None ):
                logger.info("Recording in a file operations completed...")
                cls.fAddLogDone = open("add_log_done.txt", "w")

    @classmethod
    def getEndState(cls):
        return StateHasData()

    @classmethod
    def canBeginFrom(cls, state: AnyState):
        return state.canAddData()
        
    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
        ds = self._dbManager
        # wt.execSql("use db") # TODO: seems to be an INSERT bug to require this
        tblSeq = list(range(self.LARGE_NUMBER_OF_TABLES if gConfig.larger_data else self.SMALL_NUMBER_OF_TABLES)) 
        random.shuffle(tblSeq) 
        for i in tblSeq: 
            if ( i in self.activeTable ): # wow already active
                # logger.info("Concurrent data insertion into table: {}".format(i))      
                # print("ct({})".format(i), end="", flush=True) # Concurrent insertion into table
                print("x", end="", flush=True)
            else:
                self.activeTable.add(i) # marking it active
            # No need to shuffle data sequence, unless later we decide to do non-increment insertion      
            regTableName = self.getRegTableName(i); # "db.reg_table_{}".format(i)      
            for j in range(self.LARGE_NUMBER_OF_RECORDS if gConfig.larger_data else self.SMALL_NUMBER_OF_RECORDS) : # number of records per table
                nextInt = ds.getNextInt()                
                if gConfig.record_ops:
                    self.prepToRecordOps()
                    self.fAddLogReady.write("Ready to write {} to {}\n".format(nextInt, regTableName))
                    self.fAddLogReady.flush()
                    os.fsync(self.fAddLogReady)
                sql = "insert into {} using {} tags ('{}', {}) values ('{}', {});".format(
                    regTableName, 
                    ds.getFixedSuperTableName(), 
                    ds.getNextBinary(), ds.getNextFloat(),
                    ds.getNextTick(), nextInt)
                self.execWtSql(wt, sql) 
                # Successfully wrote the data into the DB, let's record it somehow
                te.recordDataMark(nextInt)
                if gConfig.record_ops:
                    self.fAddLogDone.write("Wrote {} to {}\n".format(nextInt, regTableName))
                    self.fAddLogDone.flush()
                    os.fsync(self.fAddLogDone)
            self.activeTable.discard(i) # not raising an error, unlike remove


# Deterministic random number generator
class Dice():
    seeded = False # static, uninitialized

    @classmethod
    def seed(cls, s): # static
        if (cls.seeded):
            raise RuntimeError("Cannot seed the random generator more than once")
        cls.verifyRNG()
        random.seed(s)
        cls.seeded = True  # TODO: protect against multi-threading

    @classmethod
    def verifyRNG(cls): # Verify that the RNG is determinstic
        random.seed(0)
        x1 = random.randrange(0, 1000)
        x2 = random.randrange(0, 1000)
        x3 = random.randrange(0, 1000)
        if ( x1 != 864 or x2!=394 or x3!=776 ):
            raise RuntimeError("System RNG is not deterministic")

    @classmethod
    def throw(cls, stop): # get 0 to stop-1
        return cls.throwRange(0, stop)

    @classmethod
    def throwRange(cls, start, stop): # up to stop-1
        if ( not cls.seeded ):
            raise RuntimeError("Cannot throw dice before seeding it")
        return random.randrange(start, stop)

class LoggingFilter(logging.Filter):
    def filter(self, record: logging.LogRecord):
        if ( record.levelno >= logging.INFO ) :
            return True # info or above always log

        # Commenting out below to adjust...

        # if msg.startswith("[TRD]"):
        #     return False
        return True

class MyLoggingAdapter(logging.LoggerAdapter):    
    def process(self, msg, kwargs):
        return "[{}]{}".format(threading.get_ident() % 10000, msg), kwargs
        # return '[%s] %s' % (self.extra['connid'], msg), kwargs

class SvcManager:    
    def __init__(self):
        print("Starting TDengine Service Manager")
        signal.signal(signal.SIGTERM, self.sigIntHandler)
        signal.signal(signal.SIGINT,  self.sigIntHandler)
        signal.signal(signal.SIGUSR1, self.sigUsrHandler) # different handler!
        
        self.inSigHandler = False
        # self._status = MainExec.STATUS_RUNNING # set inside _startTaosService()
        self.svcMgrThread = None

    def _doMenu(self):
        choice = ""
        while True:
            print("\nInterrupting Service Program, Choose an Action: ")
            print("1: Resume")
            print("2: Terminate")
            print("3: Restart")
            # Remember to update the if range below
            # print("Enter Choice: ", end="", flush=True)            
            while choice == "":
                choice = input("Enter Choice: ")
                if choice != "":
                    break # done with reading repeated input
            if choice in ["1", "2", "3"]: 
                break # we are done with whole method
            print("Invalid choice, please try again.")
            choice = "" # reset
        return choice

    def sigUsrHandler(self, signalNumber, frame) :
        print("Interrupting main thread execution upon SIGUSR1")
        if self.inSigHandler : # already
            print("Ignoring repeated SIG...")
            return # do nothing if it's already not running
        self.inSigHandler = True

        choice = self._doMenu()
        if choice == "1" :
            self.sigHandlerResume() # TODO: can the sub-process be blocked due to us not reading from queue?
        elif choice == "2" :
            self.stopTaosService()
        elif choice == "3" :
            self.stopTaosService()
            self.startTaosService()
        else:
            raise RuntimeError("Invalid menu choice: {}".format(choice))

        self.inSigHandler = False

    def sigIntHandler(self, signalNumber, frame):
        print("Sig INT Handler starting...")
        if self.inSigHandler :
            print("Ignoring repeated SIG_INT...")
            return
        self.inSigHandler = True
 
        self.stopTaosService()  
        print("INT signal handler returning...")  
        self.inSigHandler = False

    def sigHandlerResume(self) :
        print("Resuming TDengine service manager thread (main thread)...\n\n")
    
    def _checkServiceManagerThread(self):
        if self.svcMgrThread: # valid svc mgr thread
            if self.svcMgrThread.isStopped(): # done?
                self.svcMgrThread.procIpcBatch() # one last time. TODO: appropriate?
                self.svcMgrThread = None # no more

    def _procIpcAll(self):
        while self.svcMgrThread : # for as long as the svc mgr thread is still here
            self.svcMgrThread.procIpcBatch() # regular processing,
            time.sleep(0.5) # pause, before next round
            self._checkServiceManagerThread()            
        print("Service Manager Thread (with subprocess) has ended, main thread now exiting...")

    def startTaosService(self):        
        if self.svcMgrThread:
            raise RuntimeError("Cannot start TAOS service when one may already be running")
        self.svcMgrThread = ServiceManagerThread() # create the object
        self.svcMgrThread.start()
        print("TAOS service started, printing out output...")
        self.svcMgrThread.procIpcBatch(trimToTarget=10, forceOutput=True) # for printing 10 lines
        print("TAOS service started")
        
    def stopTaosService(self, outputLines = 20):
        print("Terminating Service Manager Thread (SMT) execution...")
        if not self.svcMgrThread:
            raise RuntimeError("Unexpected empty svc mgr thread")
        self.svcMgrThread.stop()
        if self.svcMgrThread.isStopped():
            self.svcMgrThread.procIpcBatch(outputLines) # one last time
            self.svcMgrThread = None 
            print("----- End of TDengine Service Output -----\n")
            print("SMT execution terminated")
        else:
            print("WARNING: SMT did not terminate as expected")

    def run(self):
        self.startTaosService()
        self._procIpcAll() # pump/process all the messages
        if self.svcMgrThread: # if sig handler hasn't destroyed it by now
            self.stopTaosService() # should have started already
        
class ServiceManagerThread:
    MAX_QUEUE_SIZE = 10000

    def __init__(self):
        self._tdeSubProcess = None
        self._thread = None        
        self._status = None

    def getStatus(self):
        return self._status

    def isRunning(self):
        # return self._thread and self._thread.is_alive()
        return self._status == MainExec.STATUS_RUNNING

    def isStopping(self):
        return self._status == MainExec.STATUS_STOPPING

    def isStopped(self):
        return self._status == MainExec.STATUS_STOPPED

    # Start the thread (with sub process), and wait for the sub service
    # to become fully operational
    def start(self):        
        if self._thread :
            raise RuntimeError("Unexpected _thread")
        if self._tdeSubProcess :
            raise RuntimeError("TDengine sub process already created/running")

        self._status = MainExec.STATUS_STARTING

        self._tdeSubProcess = TdeSubProcess()        
        self._tdeSubProcess.start()

        self._ipcQueue = Queue()
        self._thread = threading.Thread(
            target=self.svcOutputReader, 
            args=(self._tdeSubProcess.getStdOut(), self._ipcQueue))
        self._thread.daemon = True # thread dies with the program
        self._thread.start()

        # wait for service to start
        for i in range(0, 10) :
            time.sleep(1.0)
            # self.procIpcBatch() # don't pump message during start up
            print("_zz_", end="", flush=True)
            if self._status == MainExec.STATUS_RUNNING :
                logger.info("[] TDengine service READY to process requests")
                return # now we've started
        raise RuntimeError("TDengine service did not start successfully") # TODO: handle this better?

    def stop(self):
        # can be called from both main thread or signal handler
        print("Terminating TDengine service running as the sub process...")
        if self.isStopped():
            print("Service already stopped")
            return            
        if self.isStopping():
            print("Service is already being stopped")
            return
        # Linux will send Control-C generated SIGINT to the TDengine process already, ref: https://unix.stackexchange.com/questions/176235/fork-and-how-signals-are-delivered-to-processes
        if not self._tdeSubProcess :
            raise RuntimeError("sub process object missing")

        self._status = MainExec.STATUS_STOPPING
        self._tdeSubProcess.stop()

        if self._tdeSubProcess.isRunning(): # still running
            print("FAILED to stop sub process, it is still running... pid = {}".format(self.subProcess.pid))
        else:
            self._tdeSubProcess = None # not running any more
            self.join() # stop the thread, change the status, etc.
            
    def join(self):
        # TODO: sanity check
        if not self.isStopping():
            raise RuntimeError("Unexpected status when ending svc mgr thread: {}".format(self._status))

        if self._thread :
            self._thread.join()
            self._thread = None   
            self._status = MainExec.STATUS_STOPPED
        else :
            print("Joining empty thread, doing nothing")

    def _trimQueue(self, targetSize):
        if targetSize <= 0:
            return # do nothing
        q = self._ipcQueue
        if (q.qsize() <= targetSize ) : # no need to trim
            return

        logger.debug("Triming IPC queue to target size: {}".format(targetSize))
        itemsToTrim = q.qsize() - targetSize
        for i in range(0, itemsToTrim) :
            try:
                q.get_nowait()
            except Empty:
                break # break out of for loop, no more trimming    
    
    TD_READY_MSG = "TDengine is initialized successfully"
    def procIpcBatch(self, trimToTarget = 0, forceOutput = False):
        self._trimQueue(trimToTarget) # trim if necessary
        # Process all the output generated by the underlying sub process, managed by IO thread
        print("<", end="", flush=True)
        while True :            
            try:  
                line = self._ipcQueue.get_nowait() # getting output at fast speed   
                self._printProgress("_o")
            except Empty:
                # time.sleep(2.3) # wait only if there's no output
                # no more output
                print(".>", end="", flush=True)
                return # we are done with THIS BATCH
            else: # got line, printing out
                if forceOutput:
                    logger.info(line)
                else:
                    logger.debug(line)
        print(">", end="", flush=True)

    _ProgressBars = ["--", "//", "||", "\\\\"]
    def _printProgress(self, msg): # TODO: assuming 2 chars
        print(msg, end="", flush=True) 
        pBar = self._ProgressBars[Dice.throw(4)]
        print(pBar, end="", flush=True)
        print('\b\b\b\b', end="", flush=True)

    def svcOutputReader(self, out: IO, queue):
        # Important Reference: https://stackoverflow.com/questions/375427/non-blocking-read-on-a-subprocess-pipe-in-python
        # print("This is the svcOutput Reader...")
        # for line in out : 
        for line in iter(out.readline, b''):
            # print("Finished reading a line: {}".format(line))
            # print("Adding item to queue...")
            line = line.decode("utf-8").rstrip()
            queue.put(line) # This might block, and then causing "out" buffer to block            
            self._printProgress("_i")

            if self._status == MainExec.STATUS_STARTING : # we are starting, let's see if we have started
                if line.find(self.TD_READY_MSG) != -1 : # found
                    self._status = MainExec.STATUS_RUNNING                              

            # Trim the queue if necessary: TODO: try this 1 out of 10 times
            self._trimQueue(self.MAX_QUEUE_SIZE * 9 // 10) # trim to 90% size

            if self.isStopping() : # TODO: use thread status instead
                print("_w", end="", flush=True) # WAITING for stopping sub process to finish its outptu

            # queue.put(line)
        print("\nNo more output from IO thread managing TDengine service") # meaning sub process must have died
        out.close()

class TdeSubProcess:    
    def __init__(self):
        self.subProcess = None

    def getStdOut(self):
        return self.subProcess.stdout

    def isRunning(self):
        return self.subProcess != None

    def start(self):
        ON_POSIX = 'posix' in sys.builtin_module_names
        svcCmd = ['../../build/build/bin/taosd', '-c', '../../build/test/cfg']
        # svcCmd = ['vmstat', '1']
        if self.subProcess : # already there
            raise RuntimeError("Corrupt process state")

        self.subProcess = subprocess.Popen(
            svcCmd, 
            stdout=subprocess.PIPE, 
            # bufsize=1, # not supported in binary mode
            close_fds=ON_POSIX) # had text=True, which interferred with reading EOF        

    def stop(self):
        if not self.subProcess:
            print("Sub process already stopped")
            return

        retCode = self.subProcess.poll()
        if retCode : # valid return code, process ended
            self.subProcess = None
        else: # process still alive, let's interrupt it
            print("Sub process is running, sending SIG_INT and waiting for it to terminate...")
            self.subProcess.send_signal(signal.SIGINT) # sub process should end, then IPC queue should end, causing IO thread to end
            try :
                self.subProcess.wait(10)
            except subprocess.TimeoutExpired as err:
                print("Time out waiting for TDengine service process to exit")
            else:
                print("TDengine service process terminated successfully from SIG_INT")
                self.subProcess = None

class ClientManager:
    def __init__(self):
        print("Starting service manager")
        signal.signal(signal.SIGTERM, self.sigIntHandler)
        signal.signal(signal.SIGINT, self.sigIntHandler)

        self._status = MainExec.STATUS_RUNNING
        self.tc = None

    def sigIntHandler(self, signalNumber, frame):
        if self._status != MainExec.STATUS_RUNNING :
            print("Ignoring repeated SIGINT...")
            return # do nothing if it's already not running
        self._status = MainExec.STATUS_STOPPING # immediately set our status

        print("Terminating program...")
        self.tc.requestToStop()

    def _printLastNumbers(self): # to verify data durability
        dbManager = DbManager(resetDb=False)
        dbc = dbManager.getDbConn()
        if dbc.query("show databases") == 0 : # no databae
            return
        if dbc.query("show tables") == 0 : # no tables
            return

        dbc.execute("use db")
        sTbName = dbManager.getFixedSuperTableName()        

        # get all regular tables
        dbc.query("select TBNAME from db.{}".format(sTbName)) # TODO: analyze result set later
        rTables = dbc.getQueryResult()

        bList = TaskExecutor.BoundedList()
        for rTbName in rTables : # regular tables
            dbc.query("select speed from db.{}".format(rTbName[0]))
            numbers = dbc.getQueryResult()
            for row in numbers :                
                # print("<{}>".format(n), end="", flush=True)
                bList.add(row[0])

        print("Top numbers in DB right now: {}".format(bList))
        print("TDengine client execution is about to start in 2 seconds...")
        time.sleep(2.0)
        dbManager = None # release?

    def prepare(self):
        self._printLastNumbers()

    def run(self):
        if gConfig.auto_start_service :
            svcMgr = SvcManager()
            svcMgr.startTaosService()

        self._printLastNumbers()

        dbManager = DbManager() # Regular function
        thPool = ThreadPool(gConfig.num_threads, gConfig.max_steps)
        self.tc = ThreadCoordinator(thPool, dbManager)
        
        self.tc.run()
        # print("exec stats: {}".format(self.tc.getExecStats()))
        # print("TC failed = {}".format(self.tc.isFailed()))        
        if gConfig.auto_start_service :
            svcMgr.stopTaosService()
        # Print exec status, etc., AFTER showing messages from the server
        self.conclude()
        # print("TC failed (2) = {}".format(self.tc.isFailed()))
        return 1 if self.tc.isFailed() else 0 # Linux return code: ref https://shapeshed.com/unix-exit-codes/

    def conclude(self):
        self.tc.printStats()
        self.tc.getDbManager().cleanUp()    


class MainExec:
    STATUS_STARTING = 1
    STATUS_RUNNING  = 2
    STATUS_STOPPING = 3
    STATUS_STOPPED  = 4

    @classmethod
    def runClient(cls):
        clientManager = ClientManager()
        return clientManager.run()

    @classmethod
    def runService(cls):
        svcManager = SvcManager()
        svcManager.run()

    @classmethod
    def runTemp(cls): # for debugging purposes
        # # Hack to exercise reading from disk, imcreasing coverage. TODO: fix
        # dbc = dbState.getDbConn()
        # sTbName = dbState.getFixedSuperTableName()   
        # dbc.execute("create database if not exists db")
        # if not dbState.getState().equals(StateEmpty()):
        #     dbc.execute("use db")     

        # rTables = None
        # try: # the super table may not exist
        #     sql = "select TBNAME from db.{}".format(sTbName)
        #     logger.info("Finding out tables in super table: {}".format(sql))
        #     dbc.query(sql) # TODO: analyze result set later
        #     logger.info("Fetching result")
        #     rTables = dbc.getQueryResult()
        #     logger.info("Result: {}".format(rTables))
        # except taos.error.ProgrammingError as err:
        #     logger.info("Initial Super table OPS error: {}".format(err))
        
        # # sys.exit()
        # if ( not rTables == None):
        #     # print("rTables[0] = {}, type = {}".format(rTables[0], type(rTables[0])))
        #     try:
        #         for rTbName in rTables : # regular tables
        #             ds = dbState
        #             logger.info("Inserting into table: {}".format(rTbName[0]))
        #             sql = "insert into db.{} values ('{}', {});".format(
        #                 rTbName[0],                    
        #                 ds.getNextTick(), ds.getNextInt())
        #             dbc.execute(sql)
        #         for rTbName in rTables : # regular tables        
        #             dbc.query("select * from db.{}".format(rTbName[0])) # TODO: check success failure
        #         logger.info("Initial READING operation is successful")       
        #     except taos.error.ProgrammingError as err:
        #         logger.info("Initial WRITE/READ error: {}".format(err))   
        
        # Sandbox testing code
        # dbc = dbState.getDbConn()
        # while True:
        #     rows = dbc.query("show databases") 
        #     print("Rows: {}, time={}".format(rows, time.time()))
        return 

def main():
    # Super cool Python argument library: https://docs.python.org/3/library/argparse.html
    parser = argparse.ArgumentParser(
        formatter_class=argparse.RawDescriptionHelpFormatter,
        description=textwrap.dedent('''\
            TDengine Auto Crash Generator (PLEASE NOTICE the Prerequisites Below)
            ---------------------------------------------------------------------
            1. You build TDengine in the top level ./build directory, as described in offical docs
            2. You run the server there before this script: ./build/bin/taosd -c test/cfg

            '''))

    parser.add_argument('-a', '--auto-start-service', action='store_true',                        
                        help='Automatically start/stop the TDengine service (default: false)')
    parser.add_argument('-c', '--connector-type', action='store', default='native', type=str,
                        help='Connector type to use: native, rest, or mixed (default: 10)')
    parser.add_argument('-d', '--debug', action='store_true',                        
                        help='Turn on DEBUG mode for more logging (default: false)')
    parser.add_argument('-e', '--run-tdengine', action='store_true',                        
                        help='Run TDengine service in foreground (default: false)')
    parser.add_argument('-l', '--larger-data', action='store_true',                        
                        help='Write larger amount of data during write operations (default: false)')
    parser.add_argument('-p', '--per-thread-db-connection', action='store_true',                        
                        help='Use a single shared db connection (default: false)')
    parser.add_argument('-r', '--record-ops', action='store_true',                        
                        help='Use a pair of always-fsynced fils to record operations performing + performed, for power-off tests (default: false)')                    
    parser.add_argument('-s', '--max-steps', action='store', default=1000, type=int,
                        help='Maximum number of steps to run (default: 100)')
    parser.add_argument('-t', '--num-threads', action='store', default=5, type=int,
                        help='Number of threads to run (default: 10)')

    global gConfig
    gConfig = parser.parse_args()
 
    # Logging Stuff
    global logger
    _logger = logging.getLogger('CrashGen') # real logger
    _logger.addFilter(LoggingFilter()) 
    ch = logging.StreamHandler()
    _logger.addHandler(ch)

    logger = MyLoggingAdapter(_logger, []) # Logging adapter, to be used as a logger

    if ( gConfig.debug ):
        logger.setLevel(logging.DEBUG) # default seems to be INFO        
    else:
        logger.setLevel(logging.INFO)
    
    Dice.seed(0) # initial seeding of dice
        
    # Run server or client
    if gConfig.run_tdengine : # run server
        MainExec.runService()
    else :
        return MainExec.runClient()

if __name__ == "__main__":
    exitCode = main()
    # print("Exiting with code: {}".format(exitCode))
    sys.exit(exitCode)