I'm trying to write a simple action server using the goal callback method as described in the tutorial in C++ over here, however I'm trying to rewrite it in Python. If it works, I would definitely suggest it as an addition to the actionlib tutorials.
I have put together more or less the whole thing, but clearly I'm missing something essential around the registration of the callbacks. As soon as I call the _as.register_goal_callback(self.goalCB()) the program will attempt to execute the callback immediately and then complain that it doesn't have a goal. The same happens for the _as.register_preempt_callback(self.preemptCB()) which preempts itself immediately. All this happens before the server is even started.
I suppose this is not meant to be happening, but I'm not sure what am I doing wrong.
[ERROR] [1523131943.200392]: Attempting to accept the next goal when a new goal is not available
[INFO] [1523131943.200585]: /averaging : Preempted
[ERROR] [1523131943.200728]: Attempt to get a goal id on an uninitialized ServerGoalHandle
[ERROR] [1523131943.200860]: Attempt to get a goal id on an uninitialized ServerGoalHandle
[ERROR] [1523131943.200988]: Attempt to set status on an uninitialized ServerGoalHandle
#! /usr/bin/env python import rospy import actionlib import actionlib_tutorials.msg from std_msgs.msg import Float32 from math import pow, sqrt, fabs class AveragingAction(object): # create messages that are used to publish feedback/result _feedback = actionlib_tutorials.msg.AveragingActionFeedback() _result = actionlib_tutorials.msg.AveragingActionResult() def __init__(self, name): self._action_name = name self._as = actionlib.SimpleActionServer(name=self._action_name, ActionSpec=actionlib_tutorials.msg.AveragingAction, auto_start=False) self._as.register_goal_callback(self.goalCB()) self._as.register_preempt_callback(self.preemptCB()) self._as.start() rospy.loginfo("Starting an ActionServer") self._sub = rospy.Subscriber("/random_number", Float32, callback=self.analysisCB) self._msg = Float32() def goalCB(self): self._data_count = 0 self._sum = 0 self._sum_sq = 0 self._goal = self._as.accept_new_goal() def preemptCB(self): rospy.loginfo("{} : Preempted".format(self._action_name)) self._as.set_preempted() ... (there is more code, but I don't think that's relevant anymore)
I have gone through the simple_action_callback.py to figure out why it is getting called, but I'm not sure I get what's going on because I'm probably missing out something with the goal registration. All that's written there is this :
## @brief Allows users to register a callback to be invoked when a new goal is available ## @param cb The callback to be invoked def register_goal_callback(self,cb): if self.execute_callback: rospy.logwarn("Cannot call SimpleActionServer.register_goal_callback() because an executeCallback exists. Not going to register it."); else: self.goal_callback = cb; Which would make me think that it would stay registered and activate only when a new goal arrives. But it activates immediately. Moreover a condition if self._as.is_new_goal_available(): comes out False when I place it inside the goalCB() which really confuses me.
I hope this is not too verbose. I can edit it down if needed.
FYI I'm using
- ROS Kinetic distribution
- Ubuntu 16.04 Xenial
- actionlib 1.11.13
- rospy 1.12.13
Originally posted by AdamSorrel on ROS Answers with karma: 65 on 2018-04-08
Post score: 0
