Unable to Delete Job from CustomJobFilterAttribute

question
1

In my custom JobFilterAttribute, i am implementing IElectStateFilter. I am trying to delete any duplicate jobs with that method name that are already running. In effect, I only want one instance of the job running at a time.

I would like to handle this without having to have a single worker server

Using MSMQ and SqlServer and Hangfire 1.4.1.

When a job is queued to run, i store the current jobId to my Tasks table

if (context.CandidateState is EnqueuedState)
{
    var e = (EnqueuedState)context.CandidateState;
    if (e.Reason != null && e.Reason.Contains("scheduler"))
    {
        task.RunningJobId = context.JobId;
        task.CurrentStatus = (byte)ScheduledTaskStatus.Queued;
        _repo.Save(task, ref tran);
    }
}

When a Task is triggered manually, I also store the JobId in the database (either using this same code using RecurringJob.Trigger(code) or BackgroundJob.Enqueue().

So in the case where the user manually runs a task and while it is still either enqueued or processing, the scheduler triggers it to run, I want to delete that scheduler triggered execution of the Task:

public void OnStateElection(ElectStateContext context)
{
  var task = GetTask(context.JobId, ref tran); // get the Task from the database
  if (!(string.IsNullOrEmpty(task.RunningJobId)) && task.RunningJobId != context.JobId) //do not allow multiple jobs to run for the same scheduled task                                        
  {      
    BackgroundJob.Delete(context.JobId);                      
  }                        
  else
  {
    // status update code
  }
}

When I try to delete the job, I get a SQL timeout with the blocking statement being:

(@id nvarchar(4000))select InvocationData, StateName, Arguments, CreatedAt from HangFire.Job where Id = @id

I’m not sure if there’s some sort of transactional lock on the OnStateElection method or what is happening.

If you have any suggestions for how to handle this or how i can delete the job, please let me know.

2

Instead of calling the Delete method

change the CandidateState property:

context.CandidateState = new DeletedState();
3

This worked, any reason why calling the delete method didn’t work in this instance? Is the method for ElectStateFilter in a transaction within Hangfire?