diff --git a/swh/scheduler/celery_backend/runner.py b/swh/scheduler/celery_backend/runner.py
index b6586e4..be37bce 100644
--- a/swh/scheduler/celery_backend/runner.py
+++ b/swh/scheduler/celery_backend/runner.py
@@ -1,115 +1,118 @@
 # Copyright (C) 2015-2018 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import arrow
+import logging
 
 from swh.scheduler import get_scheduler, compute_nb_tasks_from
-from .config import app as main_app
 
 
+logger = logging.getLogger(__name__)
 # Max batch size for tasks
 MAX_NUM_TASKS = 10000
 
 
 def run_ready_tasks(backend, app):
     """Run tasks that are ready
 
     Args:
         backend (Scheduler): backend to read tasks to schedule
         app (App): Celery application to send tasks to
 
     Returns:
         A list of dictionaries::
 
           {
             'task': the scheduler's task id,
             'backend_id': Celery's task id,
             'scheduler': arrow.utcnow()
           }
 
         The result can be used to block-wait for the tasks' results::
 
           backend_tasks = run_ready_tasks(self.scheduler, app)
           for task in backend_tasks:
               AsyncResult(id=task['backend_id']).get()
 
     """
     all_backend_tasks = []
     while True:
         cursor = backend.cursor()
         task_types = {}
         pending_tasks = []
         for task_type in backend.get_task_types(cursor=cursor):
             task_type_name = task_type['type']
             task_types[task_type_name] = task_type
             max_queue_length = task_type['max_queue_length']
             backend_name = task_type['backend_name']
             if max_queue_length:
                 try:
                     queue_length = app.get_queue_length(backend_name)
                 except ValueError:
                     queue_length = None
 
                 if queue_length is None:
                     # Running without RabbitMQ (probably a test env).
                     num_tasks = MAX_NUM_TASKS
                 else:
                     num_tasks = min(max_queue_length - queue_length,
                                     MAX_NUM_TASKS)
             else:
                 num_tasks = MAX_NUM_TASKS
             if num_tasks > 0:
                 num_tasks, num_tasks_priority = compute_nb_tasks_from(
                     num_tasks)
 
-                pending_tasks.extend(
-                    backend.grab_ready_tasks(
+                grabbed_tasks = backend.grab_ready_tasks(
                         task_type_name,
                         num_tasks=num_tasks,
                         num_tasks_priority=num_tasks_priority,
-                        cursor=cursor))
+                        cursor=cursor)
+                if grabbed_tasks:
+                    pending_tasks.extend(grabbed_tasks)
+                    logger.info('Grabbed %s tasks %s',
+                                len(grabbed_tasks), task_type_name)
 
         if not pending_tasks:
             return all_backend_tasks
 
         backend_tasks = []
         for task in pending_tasks:
             args = task['arguments']['args']
             kwargs = task['arguments']['kwargs']
 
             backend_name = task_types[task['type']]['backend_name']
             celery_result = app.send_task(
                 backend_name, args=args, kwargs=kwargs,
             )
-
             data = {
                 'task': task['id'],
                 'backend_id': celery_result.id,
                 'scheduled': arrow.utcnow(),
             }
 
             backend_tasks.append(data)
+        logger.debug('Sent %s celery tasks', len(backend_tasks))
 
         backend.mass_schedule_task_runs(backend_tasks, cursor=cursor)
-
         backend.commit()
-
         all_backend_tasks.extend(backend_tasks)
 
 
 def main():
+    from .config import app as main_app
     for module in main_app.conf.CELERY_IMPORTS:
         __import__(module)
 
     main_backend = get_scheduler('local')
     try:
         run_ready_tasks(main_backend, main_app)
     except Exception:
         main_backend.rollback()
         raise
 
 
 if __name__ == '__main__':
     main()