add logging when worker accomplish something

pipelet/worker.py

@@ -119,10 +119,13 @@ class Worker(object):
         try:
             for task in iter(self.scheduler.get_task, None):
                 self.work_dir = self.pipe.get_curr_dir(task.seg)
+                self.logger.info('Processing one task of segment %s'%task.seg)
                 task = self.execute_task(task)
                 if task.status == "done":
+                    self.logger.info('task done')
                     self.scheduler.task_done(task)
                 else:
+                    self.logger.info('task failed')
                     self.scheduler.task_failed(task)
                 n = n+1
             self.task = None