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

import getopt
import argparse
import copy

import threading
import random
import time
import logging
import datetime
import textwrap

from typing import List
from typing import Dict
from typing import Set

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
            self._dbConn = DbConn()   

        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
            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)

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()

    def getTaskExecutor(self):
        return self._te

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

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

    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
        failed = False
        while(self._curStep < maxSteps-1 and not failed):  # 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 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"
            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")
                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()
                    failed = 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--> 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 failed: # 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()

        logger.debug("Main thread ready to finish up...")
        if not failed: # 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("All worker thread finished")
        self._execStats.endExec()

    def logStats(self):
        self._execStats.logStats()

    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:
    def __init__(self):
        self._conn = None 
        self._cursor = None
        self.isOpen = False
        
    def open(self): # Open connection
        if ( self.isOpen ):
            raise RuntimeError("Cannot re-open an existing DB 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)
        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._cursor.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 close(self):
        if ( not self.isOpen ):
            raise RuntimeError("Cannot clean up database until connection is open")
        self._tdSql.close()
        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 _queryAny(self, sql) : # actual query result as an int
        if ( not self.isOpen ):
            raise RuntimeError("Cannot query database until connection is open")
        tSql = self._tdSql
        nRows = tSql.query(sql)
        if nRows != 1 :
            raise RuntimeError("Unexpected result for query: {}, rows = {}".format(sql, nRows))
        if tSql.queryRows != 1 or tSql.queryCols != 1:
            raise RuntimeError("Unexpected result set for query: {}".format(sql))
        return tSql.queryResult[0][0]

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

    def queryString(self, sql) -> str :
        return self._queryAny(sql)
    
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()
        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()
            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
            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():
    def __init__(self, curStep):
        self._curStep = curStep

    def getCurStep(self):
        return self._curStep

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

    # 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._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 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 = 0x80000000 + err.errno # positive error number
            if ( errno2 in [0x200, 0x360, 0x362, 0x381, 0x380, 0x600 ]) : # allowed errors
                self.logDebug("[=] Acceptable Taos library exception: errno=0x{:X}, msg: {}, SQL: {}".format(errno2, err, self._lastSql))
                print("e", end="", flush=True)
                self._err = err  
            else:
                self.logDebug("[=] Unexpected Taos library exception: errno=0x{:X}, msg: {}, SQL: {}".format(errno2, err, self._lastSql))
                raise
        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 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 logStats(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("----------------------------------------------------------------------")
        


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"
            for i in tblSeq: 
                regTableName = self.getRegTableName(i); # "db.reg_table_{}".format(i)  
                try:
                    nRows = self.execWtSql(wt, "drop table {}".format(regTableName))  
                except taos.error.ProgrammingError as err:
                    errno2 = 0x80000000 + err.errno # positive error number
                    if ( errno2 in [0x362]) : # allowed errors
                        logger.debug("[DB] Acceptable error when dropping a table")
                    continue

                if (not tickOutput):
                    tickOutput = True # Print only one time
                    if nRows >= 1 :
                        print("d", end="", flush=True)
                    else:
                        print("f({})".format(nRows), 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) 
                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)


# Anyone needing to carry out work should simply come here
# class WorkDispatcher():
#     def __init__(self, dbState):
#         # self.totalNumMethods = 2
#         self.tasks = [
#             # CreateTableTask(dbState), # Obsolete
#             # DropTableTask(dbState),
#             # AddDataTask(dbState),
#         ]

#     def throwDice(self):
#         max = len(self.tasks) - 1 
#         dRes = random.randint(0, max)
#         # logger.debug("Threw the dice in range [{},{}], and got: {}".format(0,max,dRes))
#         return dRes

#     def pickTask(self):
#         dice = self.throwDice()
#         return self.tasks[dice]

#     def doWork(self, workerThread):
#         task = self.pickTask()
#         task.execute(workerThread)

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

        msg = record.msg
        # print("type = {}, value={}".format(type(msg), msg))
        # sys.exit()

        # Commenting out below to adjust...

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

class MainExec:
    @classmethod
    def runClient(cls):
        # resetDb = False # DEBUG only
        # dbState = DbState(resetDb)  # DBEUG only!
        dbManager = DbManager() # Regular function
        Dice.seed(0) # initial seeding of dice
        thPool = ThreadPool(gConfig.num_threads, gConfig.max_steps)
        tc = ThreadCoordinator(thPool, dbManager)
        
        tc.run()
        tc.logStats()
        dbManager.cleanUp()    

    @classmethod
    def runService(cls):
        print("Running service...")

    @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('-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_false',                        
                        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()
    # if len(sys.argv) == 1:
    #     parser.print_help()
    #     sys.exit()
 
    global logger
    logger = logging.getLogger('CrashGen')
    logger.addFilter(LoggingFilter())
    if ( gConfig.debug ):
        logger.setLevel(logging.DEBUG) # default seems to be INFO        
    else:
        logger.setLevel(logging.INFO)
    ch = logging.StreamHandler()
    logger.addHandler(ch)

    if gConfig.run_tdengine : # run server
        MainExec.runService()
    else :
        MainExec.runClient()

    
    # logger.info("Crash_Gen execution finished")

if __name__ == "__main__":
    main()