Cannot remove an Ended Task (windowed scheduler)

[IzabellaRaulin]

What happened:

An "Ended" task cannot be removed - neither directly removing nor after prior stopping

This happens for a windowed schedule for which stop_timestamp is defined. That means that after this time the task is ended - this is related to changing the status from "Running" to "Ended" in line pkg/schedule/windowed_schedule.go#L101.

Steps to reproduce it

1. Run an exemplary task manifest with window schedule, for example:

  "version": 1,
  "schedule": {
    "type": "windowed",
    "interval": "3s",
    "start_timestamp": "2017-02-15T13:20:56+01:00",
    "stop_timestamp": "2017-02-15T13:48:35+01:00"
  },
  "workflow": {
   [...]
}

2. After a time stop_timestamp the state of task should be "Ended"

$ snaptel task list
ID                                       NAME                                            STATE           HIT     MISS    FAIL    CREATED                 LAST FAILURE
5db259f7-3403-421d-896a-78aa15031c80     Task-5db259f7-3403-421d-896a-78aa15031c80       Ended           38      0       0       1:46PM 2-15-2017

3. Try to remove the task:

$ snaptel task remove 5db259f7-3403-421d-896a-78aa15031c80

Error stopping task:
Task must be stopped

4. So, let's stop the task at first and then try to remove it once again:

$ snaptel task stop 5db259f7-3403-421d-896a-78aa15031c80
Task stopped:
ID: 5db259f7-3403-421d-896a-78aa15031c80

Notice that even stop command looks like be executed successfully, the state of task does NOT change to Stopped (it is still Ended)

snaptel task list
ID                                       NAME                                            STATE           HIT     MISS    FAIL    CREATED                 LAST FAILURE
5db259f7-3403-421d-896a-78aa15031c80     Task-5db259f7-3403-421d-896a-78aa15031c80       Ended           38      0       0       1:46PM 2-15-2017

Still, cannot remove this task even after trying to stop it a prior:

$ snaptel task remove 5db259f7-3403-421d-896a-78aa15031c80
Error stopping task:
Task must be stopped

It looks like a standstill.

[andrzej-k]

Ended state should also probably be described here: https://github.com/intelsdi-x/snap/blob/master/docs/TASKS.md#task-states

[IzabellaRaulin]

What can be added, ideally an Ended Task should be something that can be removed without having to stop, so it would be similar what has been done for Disabled Task in #1043.