[entities] improve workflow management of CeleryTasks (by celery-monitor)...

[entities] improve workflow management of CeleryTasks (by celery-monitor) robustness (related to #16640842)

the transition may fail (if for some race-like reasons it has already been fired).

Also ensure some CeleryTask changes are commited (celery-monitor)
since the transaction may be rolled back during the WF management part of the
on_event() method.

entities.py

@@ -22,6 +22,7 @@ import warnings
 import celery
 from celery.result import AsyncResult, from_serializable
 
+from cubicweb import ValidationError
 from cubicweb.entities import AnyEntity, fetch_config
 from cubicweb.view import EntityAdapter
 from cubicweb.predicates import is_instance
@@ -329,6 +330,7 @@ class CeleryTaskAdapter(ICeleryTask):
                 CeleryTaskAdapter.info('set %s name to %s', entity.task_id,
                                        event['name'])
                 entity.cw_set(task_name=event['name'])
+            cnx.commit()
 
         elif event['type'] == 'task-succeeded':
             rset = cnx.find('CeleryTask', task_id=event['uuid'])
@@ -339,6 +341,7 @@ class CeleryTaskAdapter(ICeleryTask):
                     event['uuid'], asresult.result, event['result'])
                 root = rset.one()
                 root.cw_adapt_to('ICeleryTask').attach_result(asresult)
+                cnx.commit()
             else:
                 CeleryTaskAdapter.warning(
                     'Cannot find a cw entity for %s', event['uuid'])
@@ -355,10 +358,17 @@ class CeleryTaskAdapter(ICeleryTask):
                 return
             entity = rset.one()
             transition = tr_map[event['type']]
-            entity.cw_adapt_to('IWorkflowable').fire_transition(
-                transition, event.get('exception'))
-            CeleryTaskAdapter.info('<CeleryTask %s (task_id %s)> %s',
-                                   entity.eid, entity.task_id, transition)
+            try:
+                entity.cw_adapt_to('IWorkflowable').fire_transition(
+                    transition, event.get('exception'))
+                CeleryTaskAdapter.info('<CeleryTask %s (task_id %s)> %s',
+                                       entity.eid, entity.task_id, transition)
+                cnx.commit()
+            except ValidationError as exc:
+                CeleryTaskAdapter.warning(
+                    '<CeleryTask %s (task_id %s)> faild to fire %s:\n%s',
+                    entity.eid, entity.task_id, transition, exc)
+                cnx.rollback()
 
     @staticmethod
     def on_monitor_start(cnx):