Cancel event in Python Gp tools with arcpy

This isn't an answer, but an elaboration on the question. I've published an asynchronous gp service using the code shown below. If the user cancels, the result object returned does indicate that. However, the loop runs for the full number of seconds. I would like to break out of the loop if user has canceled.

def execute(self, parameters, messages):
    secondstosleep  = int(parameters[0].valueAsText)
    output = parameters[1].valueAsText

    if secondstosleep < 0:
        messages.addErrorMessage("{0} : less than zero.".format(secondstosleep))
        raise arcpy.ExecuteError
    messages.addMessage("starting to sleep for {0} seconds".format(secondstosleep))
    slept = 0
    for t in xrange(0,secondstosleep):
        # would like to break if user has canceled
        # check for cancel here and break
        slept = slept + 1
        time.sleep(1)
    messages.addMessage("slept for {0} seconds".format(slept))
    return

The only way I can think of is the use of Progressor in Arcpy. Using the Progressor, once the user press the cancel button the loop breaks. Then you can check the resulting object to see whether it is canceled by the user. Here is a sample code:

def execute(self, parameters, messages):
    import time
    n=30
    p=1
    arcpy.SetProgressor("step",
                        "Step progressor: Counting from 0 to {0}".format(n),
                        0, n, p)
    loopTime=.3
    for i in range(n):
        if (i % p) == 0:
            ##            # would like to break if user has canceled
            arcpy.SetProgressorLabel("Iteration: {0}".format(i))
            arcpy.SetProgressorPosition(i)
            #print(i)
            time.sleep(loopTime)

    arcpy.SetProgressorLabel("Iteration: {0}".format(i + 1))
    arcpy.SetProgressorPosition(i + 1)
    return

If you use arcmap 10.4 and up, you can set arcpy.env.autoCancelling = False to do the clean up work yourself. Example from official website.

import arcpy
arcpy.env.autoCancelling = False

def my_function(tables, output):
    temp_tables = []
    try:
        for table in tables:
            temp_tables.append(arcpy.CopyRows_management(table, '#')[0])
            # If isCancelled is True this means that the cancel button
            # has been pressed
            if arcpy.env.isCancelled:
               raise RuntimeError('Tool has been cancelled')
            arcpy.Merge_management(tables, output)
     except RuntimeError as err:
         arcpy.AddError(err)
     finally:
        # If tool is cancelled or finishes successfully, clean up intermediate data
        if temp_tables:
            for temp_table in temp_tables:
                arcpy.Delete_management(temp_table)