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Task Execution with Cancel Logic


Nested if statements with 3 different parametersDetermining if current thread is executingProperly creating a Task to poll and dispatch child tasks with cancellation for eachGeneric Task Blocking QueueUsing Task<T> and actions for simple threading?BackgroundWorker vs TPL ProgressBar ExerciseReactiveUI and Rx background calculations with cancellationSecure client-side encryption of user contentTask Wrappers for starting operation only if previous task has finishedFilter data with optional parameters






.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








1












$begingroup$


In my assignment I am executing a long running NodeJs script from C# using EdgeJs. Since the script may take a long time to execute, I also want to provide user an option to Cancel the script execution in the middle. The cancellation status is maintained in the database and function IsScripteExecutionCancelled returns true if the user decides to cancel the execution.



To achieve this I am executing script in a background thread using Task.Run(). The main thread contains a while loop that runs until the ScriptExecution is over or is cancelled. I can solve this problem using native System.Threading.Thread, but here I am trying to do it using TPL. Here is the code I have put in place:



bool executionStarted = false;
bool taskCompleted = false;
Result returnValue;

CancellationTokenSource tokenSource = new CancellationTokenSource();
CancellationToken token = tokenSource.Token;

Task executionTask;
while (!(taskCompleted || token.IsCancellationRequested))

if (!executionStarted)

executionStarted = true;
executionTask = Task.Run(() =>

returnValue = ExecuteScript();
taskCompleted = true;
, token);

bool taskExecutionCancelled = IsScripteExecutionCancelled();
if (taskExecutionCancelled)

tokenSource.Cancel();



if(token.IsCancellationRequested)
returnValue= GetDefaultValueForCancellation();

return returnValue;


So, if IsScripteExecutionCancelled returns true the program will come out of the loop and will check if the script was cancelled, in which case I will return a default response. If the ExecuteScript completes my program will return the value returned by function ExecuteScript. I am able to get the desired results using this implementation however I would like to get it validated.



Question: Is it the right way to address this problem?










share|improve this question











$endgroup$




bumped to the homepage by Community 12 mins ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.










  • 1




    $begingroup$
    You are going to have to provide more context. It is unclear what this code is suppose to be doing.
    $endgroup$
    – Nkosi
    Mar 13 '18 at 11:33










  • $begingroup$
    This question is incomplete. To help reviewers give you better answers, please add sufficient context to your question. The more you tell us about what your code does and what the purpose of doing that is, the easier it will be for reviewers to help you. Questions should include a description of what the code does
    $endgroup$
    – Dannnno
    Mar 13 '18 at 13:57

















1












$begingroup$


In my assignment I am executing a long running NodeJs script from C# using EdgeJs. Since the script may take a long time to execute, I also want to provide user an option to Cancel the script execution in the middle. The cancellation status is maintained in the database and function IsScripteExecutionCancelled returns true if the user decides to cancel the execution.



To achieve this I am executing script in a background thread using Task.Run(). The main thread contains a while loop that runs until the ScriptExecution is over or is cancelled. I can solve this problem using native System.Threading.Thread, but here I am trying to do it using TPL. Here is the code I have put in place:



bool executionStarted = false;
bool taskCompleted = false;
Result returnValue;

CancellationTokenSource tokenSource = new CancellationTokenSource();
CancellationToken token = tokenSource.Token;

Task executionTask;
while (!(taskCompleted || token.IsCancellationRequested))

if (!executionStarted)

executionStarted = true;
executionTask = Task.Run(() =>

returnValue = ExecuteScript();
taskCompleted = true;
, token);

bool taskExecutionCancelled = IsScripteExecutionCancelled();
if (taskExecutionCancelled)

tokenSource.Cancel();



if(token.IsCancellationRequested)
returnValue= GetDefaultValueForCancellation();

return returnValue;


So, if IsScripteExecutionCancelled returns true the program will come out of the loop and will check if the script was cancelled, in which case I will return a default response. If the ExecuteScript completes my program will return the value returned by function ExecuteScript. I am able to get the desired results using this implementation however I would like to get it validated.



Question: Is it the right way to address this problem?










share|improve this question











$endgroup$




bumped to the homepage by Community 12 mins ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.










  • 1




    $begingroup$
    You are going to have to provide more context. It is unclear what this code is suppose to be doing.
    $endgroup$
    – Nkosi
    Mar 13 '18 at 11:33










  • $begingroup$
    This question is incomplete. To help reviewers give you better answers, please add sufficient context to your question. The more you tell us about what your code does and what the purpose of doing that is, the easier it will be for reviewers to help you. Questions should include a description of what the code does
    $endgroup$
    – Dannnno
    Mar 13 '18 at 13:57













1












1








1


1



$begingroup$


In my assignment I am executing a long running NodeJs script from C# using EdgeJs. Since the script may take a long time to execute, I also want to provide user an option to Cancel the script execution in the middle. The cancellation status is maintained in the database and function IsScripteExecutionCancelled returns true if the user decides to cancel the execution.



To achieve this I am executing script in a background thread using Task.Run(). The main thread contains a while loop that runs until the ScriptExecution is over or is cancelled. I can solve this problem using native System.Threading.Thread, but here I am trying to do it using TPL. Here is the code I have put in place:



bool executionStarted = false;
bool taskCompleted = false;
Result returnValue;

CancellationTokenSource tokenSource = new CancellationTokenSource();
CancellationToken token = tokenSource.Token;

Task executionTask;
while (!(taskCompleted || token.IsCancellationRequested))

if (!executionStarted)

executionStarted = true;
executionTask = Task.Run(() =>

returnValue = ExecuteScript();
taskCompleted = true;
, token);

bool taskExecutionCancelled = IsScripteExecutionCancelled();
if (taskExecutionCancelled)

tokenSource.Cancel();



if(token.IsCancellationRequested)
returnValue= GetDefaultValueForCancellation();

return returnValue;


So, if IsScripteExecutionCancelled returns true the program will come out of the loop and will check if the script was cancelled, in which case I will return a default response. If the ExecuteScript completes my program will return the value returned by function ExecuteScript. I am able to get the desired results using this implementation however I would like to get it validated.



Question: Is it the right way to address this problem?










share|improve this question











$endgroup$




In my assignment I am executing a long running NodeJs script from C# using EdgeJs. Since the script may take a long time to execute, I also want to provide user an option to Cancel the script execution in the middle. The cancellation status is maintained in the database and function IsScripteExecutionCancelled returns true if the user decides to cancel the execution.



To achieve this I am executing script in a background thread using Task.Run(). The main thread contains a while loop that runs until the ScriptExecution is over or is cancelled. I can solve this problem using native System.Threading.Thread, but here I am trying to do it using TPL. Here is the code I have put in place:



bool executionStarted = false;
bool taskCompleted = false;
Result returnValue;

CancellationTokenSource tokenSource = new CancellationTokenSource();
CancellationToken token = tokenSource.Token;

Task executionTask;
while (!(taskCompleted || token.IsCancellationRequested))

if (!executionStarted)

executionStarted = true;
executionTask = Task.Run(() =>

returnValue = ExecuteScript();
taskCompleted = true;
, token);

bool taskExecutionCancelled = IsScripteExecutionCancelled();
if (taskExecutionCancelled)

tokenSource.Cancel();



if(token.IsCancellationRequested)
returnValue= GetDefaultValueForCancellation();

return returnValue;


So, if IsScripteExecutionCancelled returns true the program will come out of the loop and will check if the script was cancelled, in which case I will return a default response. If the ExecuteScript completes my program will return the value returned by function ExecuteScript. I am able to get the desired results using this implementation however I would like to get it validated.



Question: Is it the right way to address this problem?







c# task-parallel-library






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Mar 14 '18 at 16:48









Sᴀᴍ Onᴇᴌᴀ

10.3k62168




10.3k62168










asked Mar 13 '18 at 10:33









AashishAashish

1395




1395





bumped to the homepage by Community 12 mins ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.







bumped to the homepage by Community 12 mins ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.









  • 1




    $begingroup$
    You are going to have to provide more context. It is unclear what this code is suppose to be doing.
    $endgroup$
    – Nkosi
    Mar 13 '18 at 11:33










  • $begingroup$
    This question is incomplete. To help reviewers give you better answers, please add sufficient context to your question. The more you tell us about what your code does and what the purpose of doing that is, the easier it will be for reviewers to help you. Questions should include a description of what the code does
    $endgroup$
    – Dannnno
    Mar 13 '18 at 13:57












  • 1




    $begingroup$
    You are going to have to provide more context. It is unclear what this code is suppose to be doing.
    $endgroup$
    – Nkosi
    Mar 13 '18 at 11:33










  • $begingroup$
    This question is incomplete. To help reviewers give you better answers, please add sufficient context to your question. The more you tell us about what your code does and what the purpose of doing that is, the easier it will be for reviewers to help you. Questions should include a description of what the code does
    $endgroup$
    – Dannnno
    Mar 13 '18 at 13:57







1




1




$begingroup$
You are going to have to provide more context. It is unclear what this code is suppose to be doing.
$endgroup$
– Nkosi
Mar 13 '18 at 11:33




$begingroup$
You are going to have to provide more context. It is unclear what this code is suppose to be doing.
$endgroup$
– Nkosi
Mar 13 '18 at 11:33












$begingroup$
This question is incomplete. To help reviewers give you better answers, please add sufficient context to your question. The more you tell us about what your code does and what the purpose of doing that is, the easier it will be for reviewers to help you. Questions should include a description of what the code does
$endgroup$
– Dannnno
Mar 13 '18 at 13:57




$begingroup$
This question is incomplete. To help reviewers give you better answers, please add sufficient context to your question. The more you tell us about what your code does and what the purpose of doing that is, the easier it will be for reviewers to help you. Questions should include a description of what the code does
$endgroup$
– Dannnno
Mar 13 '18 at 13:57










2 Answers
2






active

oldest

votes


















0












$begingroup$


Is there a better way of doing Task cancellation than the one I implemented




There's no task cancellation implemented here. By passing a token to Task.Run you just make the returned task IsCanceled equal to true in case it cancels itself (without, it gets IsFaulted by the OperationCanceledException). But you need (at least) to pass the token to DoSomeWork, because that has to check the token and cancel itself.



Task cancellation works through cooperation of the to-be-canceled task and has nothing to do with Thread.Abort.






share|improve this answer









$endgroup$




















    0












    $begingroup$

    you create a variable here and use it only once




    bool taskExecutionCancelled = IsScripteExecutionCancelled();
    if (taskExecutionCancelled)

    tokenSource.Cancel();




    I would just use the method in the if statement, like



    if (IsScripteExecutionCancelled())

    tokenSource.Cancel();



    if you were going to use this value somewhere else and didn't want it evaluated again, then you could assign it to a variable, but then you need to keep in mind that calling the variable will not run the method.






    share|improve this answer











    $endgroup$













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      2 Answers
      2






      active

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      2 Answers
      2






      active

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      active

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      active

      oldest

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      0












      $begingroup$


      Is there a better way of doing Task cancellation than the one I implemented




      There's no task cancellation implemented here. By passing a token to Task.Run you just make the returned task IsCanceled equal to true in case it cancels itself (without, it gets IsFaulted by the OperationCanceledException). But you need (at least) to pass the token to DoSomeWork, because that has to check the token and cancel itself.



      Task cancellation works through cooperation of the to-be-canceled task and has nothing to do with Thread.Abort.






      share|improve this answer









      $endgroup$

















        0












        $begingroup$


        Is there a better way of doing Task cancellation than the one I implemented




        There's no task cancellation implemented here. By passing a token to Task.Run you just make the returned task IsCanceled equal to true in case it cancels itself (without, it gets IsFaulted by the OperationCanceledException). But you need (at least) to pass the token to DoSomeWork, because that has to check the token and cancel itself.



        Task cancellation works through cooperation of the to-be-canceled task and has nothing to do with Thread.Abort.






        share|improve this answer









        $endgroup$















          0












          0








          0





          $begingroup$


          Is there a better way of doing Task cancellation than the one I implemented




          There's no task cancellation implemented here. By passing a token to Task.Run you just make the returned task IsCanceled equal to true in case it cancels itself (without, it gets IsFaulted by the OperationCanceledException). But you need (at least) to pass the token to DoSomeWork, because that has to check the token and cancel itself.



          Task cancellation works through cooperation of the to-be-canceled task and has nothing to do with Thread.Abort.






          share|improve this answer









          $endgroup$




          Is there a better way of doing Task cancellation than the one I implemented




          There's no task cancellation implemented here. By passing a token to Task.Run you just make the returned task IsCanceled equal to true in case it cancels itself (without, it gets IsFaulted by the OperationCanceledException). But you need (at least) to pass the token to DoSomeWork, because that has to check the token and cancel itself.



          Task cancellation works through cooperation of the to-be-canceled task and has nothing to do with Thread.Abort.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Mar 13 '18 at 15:36









          HaukingerHaukinger

          1194




          1194























              0












              $begingroup$

              you create a variable here and use it only once




              bool taskExecutionCancelled = IsScripteExecutionCancelled();
              if (taskExecutionCancelled)

              tokenSource.Cancel();




              I would just use the method in the if statement, like



              if (IsScripteExecutionCancelled())

              tokenSource.Cancel();



              if you were going to use this value somewhere else and didn't want it evaluated again, then you could assign it to a variable, but then you need to keep in mind that calling the variable will not run the method.






              share|improve this answer











              $endgroup$

















                0












                $begingroup$

                you create a variable here and use it only once




                bool taskExecutionCancelled = IsScripteExecutionCancelled();
                if (taskExecutionCancelled)

                tokenSource.Cancel();




                I would just use the method in the if statement, like



                if (IsScripteExecutionCancelled())

                tokenSource.Cancel();



                if you were going to use this value somewhere else and didn't want it evaluated again, then you could assign it to a variable, but then you need to keep in mind that calling the variable will not run the method.






                share|improve this answer











                $endgroup$















                  0












                  0








                  0





                  $begingroup$

                  you create a variable here and use it only once




                  bool taskExecutionCancelled = IsScripteExecutionCancelled();
                  if (taskExecutionCancelled)

                  tokenSource.Cancel();




                  I would just use the method in the if statement, like



                  if (IsScripteExecutionCancelled())

                  tokenSource.Cancel();



                  if you were going to use this value somewhere else and didn't want it evaluated again, then you could assign it to a variable, but then you need to keep in mind that calling the variable will not run the method.






                  share|improve this answer











                  $endgroup$



                  you create a variable here and use it only once




                  bool taskExecutionCancelled = IsScripteExecutionCancelled();
                  if (taskExecutionCancelled)

                  tokenSource.Cancel();




                  I would just use the method in the if statement, like



                  if (IsScripteExecutionCancelled())

                  tokenSource.Cancel();



                  if you were going to use this value somewhere else and didn't want it evaluated again, then you could assign it to a variable, but then you need to keep in mind that calling the variable will not run the method.







                  share|improve this answer














                  share|improve this answer



                  share|improve this answer








                  edited Mar 14 '18 at 18:59

























                  answered Mar 14 '18 at 17:45









                  MalachiMalachi

                  25.6k774177




                  25.6k774177



























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