TaskCancellation (#7669)

* Smol comment

* WIP, not passing ray.init

* Fixed small problem

* wip

* Pseudo interrupt things

* Basic prototype operational

* correct proc title

* Mostly done

* Cleanup

* cleaner raylet error

* Cleaning up a few loose ends

* Fixing Race Conds

* Prelim testing

* Fixing comments and adding second_check for kill

* Working_new_impl

* demo_ready

* Fixing my english

* Fixing a few problems

* Small problems

* Cleaning up

* Response to changes

* Fixing error passing

* Merged to master

* fixing lock

* Cleaning up print statements

* Format

* Fixing Unit test build failure

* mock_worker fix

* java_fix

* Canel

* Switching to Cancel

* Responding to Review

* FixFormatting

* Lease cancellation

* FInal comments?

* Moving exist check to CoreWorker

* Fix Actor Transport Test

* Fixing task manager test

* chaning clock repr

* Fix build

* fix white space

* lint fix

* Updating to medium size

* Fixing Java test compilation issue

* lengthen bad timeouts

python/ray/worker.py

@@ -1661,12 +1661,33 @@ def kill(actor):
     if not isinstance(actor, ray.actor.ActorHandle):
         raise ValueError("ray.kill() only supported for actors. "
                          "Got: {}.".format(type(actor)))
-
     worker = ray.worker.global_worker
     worker.check_connected()
     worker.core_worker.kill_actor(actor._ray_actor_id, False)
 
 
+def cancel(object_id, force=False):
+    """Kill a task forcefully.
+
+    This will interrupt any running tasks on the actor, causing them to fail
+    immediately. Any atexit handlers installed in the actor will still be run.
+
+    If this actor is reconstructable, it will be attempted to be reconstructed.
+
+    Args:
+        id (ActorHandle or ObjectID): Handle for the actor to kill or ObjectID
+        of the task to kill.
+    """
+    worker = ray.worker.global_worker
+    worker.check_connected()
+
+    if not isinstance(object_id, ray.ObjectID):
+        raise TypeError(
+            "ray.cancel() only supported for non-actor object IDs. "
+            "Got: {}.".format(type(object_id)))
+    return worker.core_worker.cancel_task(object_id, force)
+
+
 def _mode(worker=global_worker):
     """This is a wrapper around worker.mode.