[entities] CeleryTaskAdapter: revoke child tasks recursively

When a task is revoked, revoke child tasks as well.
Also add a `child_tasks` property on CeleryTaskAdapter to recurse over child
tasks.

entities.py

@@ -130,6 +130,12 @@ class CeleryTask(AnyEntity):
             for ptask in task.parent_tasks:
                 yield ptask
 
+    def child_tasks(self):
+        yield self
+        for task in self.reverse_parent_task:
+            for ctask in task.child_tasks():
+                yield ctask
+
 
 class ICeleryTask(EntityAdapter):
     __regid__ = 'ICeleryTask'
@@ -251,6 +257,11 @@ class CeleryTaskAdapter(ICeleryTask):
     def task_name(self):
         return self.entity.task_name
 
+    def revoke(self, terminate=True, signal='SIGKILL'):
+        to_revoke = set([e.task_id for e in self.entity.child_tasks()])
+        return celery.task.control.revoke(
+            list(to_revoke), terminate=terminate, signal=signal)
+
     def attach_result(self, result):
         def tree(result, seen=None):
             if seen is None:

test/test_celerytask.py

@@ -232,6 +232,37 @@ class CeleryTaskTC(BaseCeleryTaskTC):
             revoke.assert_called_once_with([task.task_id], signal='SIGKILL',
                                            terminate=True)
 
+    def test_multi_revoke(self):
+        with self.admin_access.cnx() as cnx:
+            s = celery.signature
+            task_ids = []
+
+            def success():
+                task = s("success")
+                task_ids.append(task.freeze().task_id)
+                return task
+
+            def group(*tasks):
+                g = celery.group(*tasks)
+                task_ids.append(g.freeze().id)
+                return g
+
+            graph = group(
+                group(success(), success()),
+                group(success(), success()),
+                success())
+            task = start_async_task(cnx, graph)
+            cnx.commit()
+            self.assertEqual(set(task_ids), set([
+                t.task_id for t in task.child_tasks()]))
+            with mock.patch('celery.app.control.Control.revoke') as revoke:
+                task.cw_adapt_to('ICeleryTask').revoke()
+            self.assertEqual(revoke.call_count, 1)
+            args, kwargs = revoke.call_args
+            self.assertEqual(len(args), 1)
+            self.assertEqual(set(task_ids), set(args[0]))
+            self.assertEqual({'terminate': True, 'signal': 'SIGKILL'}, kwargs)
+
 
 if __name__ == '__main__':
     from unittest import main