action_server.py

Go to the documentation of this file.

# Copyright (c) 2009, Willow Garage, Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#     * Redistributions of source code must retain the above copyright
#       notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above copyright
#       notice, this list of conditions and the following disclaimer in the
#       documentation and/or other materials provided with the distribution.
#     * Neither the name of the Willow Garage, Inc. nor the names of its
#       contributors may be used to endorse or promote products derived from
#       this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
# Author: Alexander Sorokin.
# Based on C++ action_server.h by Eitan Marder-Eppstein
import rospy
import threading
 
from actionlib_msgs.msg import GoalID, GoalStatus, GoalStatusArray
 
from actionlib.goal_id_generator import GoalIDGenerator
from actionlib.status_tracker import StatusTracker
 
from actionlib.handle_tracker_deleter import HandleTrackerDeleter
from actionlib.server_goal_handle import ServerGoalHandle
 
from actionlib.exceptions import ActionException
 
 
def nop_cb(goal_handle):
    pass
 
 
 
class ActionServer:
    
    def __init__(self, ns,  ActionSpec, goal_cb, cancel_cb=nop_cb, auto_start=True):
        self.ns = ns
 
        try:
            a = ActionSpec()
 
            self.ActionSpec = ActionSpec
            self.ActionGoal = type(a.action_goal)
            self.ActionResult = type(a.action_result)
            self.ActionResultType = type(a.action_result.result)
            self.ActionFeedback = type(a.action_feedback)
        except AttributeError:
            raise ActionException("Type is not an action spec: %s" % str(ActionSpec))
 
        self.goal_sub = None
        self.cancel_sub = None
        self.status_pub = None
        self.result_pub = None
        self.feedback_pub = None
 
        self.lock = threading.RLock()
 
        self.status_timer = None
 
        self.status_list = []
 
        self.last_cancel = rospy.Time()
        self.status_list_timeout = rospy.Duration()
 
        self.id_generator = GoalIDGenerator()
 
        self.goal_callback = goal_cb
        assert(self.goal_callback)
 
        self.cancel_callback = cancel_cb
        self.auto_start = auto_start
 
        self.started = False
 
        if self.auto_start:
            rospy.logwarn("You've passed in true for auto_start to the python action server, you should always pass "
                          "in false to avoid race conditions.")
            self.start()
 
    
    def register_goal_callback(self, cb):
        self.goal_callback = cb
 
    
    def register_cancel_callback(self, cancel_cb):
        self.cancel_callback = cancel_cb
 
    
    def start(self):
        with self.lock:
            self.initialize()
            self.started = True
            self.publish_status()
 
    
    def stop(self):
        with self.lock:
            self.started = False
            self.status_timer.shutdown()
            self.goal_sub.unregister()
            self.cancel_sub.unregister()
            self.status_pub.unregister()
            self.feedback_pub.unregister()
            self.result_pub.unregister()
 
    
    def initialize(self):
        self.pub_queue_size = rospy.get_param('actionlib_server_pub_queue_size', 50)
        if self.pub_queue_size < 0:
            self.pub_queue_size = 50
        self.status_pub = rospy.Publisher(rospy.remap_name(self.ns)+"/status", GoalStatusArray, latch=True, queue_size=self.pub_queue_size)
        self.result_pub = rospy.Publisher(rospy.remap_name(self.ns)+"/result", self.ActionResult, queue_size=self.pub_queue_size)
        self.feedback_pub = rospy.Publisher(rospy.remap_name(self.ns)+"/feedback", self.ActionFeedback, queue_size=self.pub_queue_size)
 
        self.sub_queue_size = rospy.get_param('actionlib_server_sub_queue_size', -1)
        if self.sub_queue_size < 0:
            self.sub_queue_size = None
        self.goal_sub = rospy.Subscriber(rospy.remap_name(self.ns)+"/goal", self.ActionGoal, callback=self.internal_goal_callback, queue_size=self.sub_queue_size)
 
        self.cancel_sub = rospy.Subscriber(rospy.remap_name(self.ns)+"/cancel", GoalID, callback=self.internal_cancel_callback, queue_size=self.sub_queue_size)
 
        # read the frequency with which to publish status from the parameter server
        # if not specified locally explicitly, use search param to find actionlib_status_frequency
        resolved_status_frequency_name = rospy.remap_name(self.ns)+"/status_frequency"
        if rospy.has_param(resolved_status_frequency_name):
            self.status_frequency = rospy.get_param(resolved_status_frequency_name, 5.0)
            rospy.logwarn("You're using the deprecated status_frequency parameter, please switch to actionlib_status_frequency.")
        else:
            search_status_frequency_name = rospy.search_param("actionlib_status_frequency")
            if search_status_frequency_name is None:
                self.status_frequency = 5.0
            else:
                self.status_frequency = rospy.get_param(search_status_frequency_name, 5.0)
 
        status_list_timeout = rospy.get_param(rospy.remap_name(self.ns)+"/status_list_timeout", 5.0)
        self.status_list_timeout = rospy.Duration(status_list_timeout)
 
        if self.status_frequency > 0.0:
            status_period = rospy.Duration(1.0 / self.status_frequency)
            self.status_timer = rospy.Timer(status_period, self.publish_status_async)
 
    
    def publish_result(self, status, result):
        with self.lock:
            ar = self.ActionResult()
            ar.header.stamp = rospy.Time.now()
            ar.status = status
            ar.result = result
            if not rospy.is_shutdown():
                self.result_pub.publish(ar)
            self.publish_status()
 
    
    def publish_feedback(self, status, feedback):
        with self.lock:
            af = self.ActionFeedback()
            af.header.stamp = rospy.Time.now()
            af.status = status
            af.feedback = feedback
            if not rospy.is_shutdown():
                self.feedback_pub.publish(af)
 
    
    def internal_cancel_callback(self, goal_id):
        with self.lock:
 
            # if we're not started... then we're not actually going to do anything
            if not self.started:
                return
 
            # we need to handle a cancel for the user
            rospy.logdebug("The action server has received a new cancel request")
 
            goal_id_found = False
            for st in self.status_list[:]:
                # check if the goal id is zero or if it is equal to the goal id of
                # the iterator or if the time of the iterator warrants a cancel
 
                cancel_everything = (goal_id.id == "" and goal_id.stamp == rospy.Time())   # rospy::Time()) #id and stamp 0 --> cancel everything
                cancel_this_one = (goal_id.id == st.status.goal_id.id)   # ids match... cancel that goal
                cancel_before_stamp = (goal_id.stamp != rospy.Time() and st.status.goal_id.stamp <= goal_id.stamp)  # //stamp != 0 --> cancel everything before stamp
 
                if cancel_everything or cancel_this_one or cancel_before_stamp:
                    # we need to check if we need to store this cancel request for later
                    if goal_id.id == st.status.goal_id.id:
                        goal_id_found = True
 
                    # attempt to get the handle_tracker for the list item if it exists
                    handle_tracker = st.handle_tracker
 
                    if handle_tracker is None:
                        # if the handle tracker is expired, then we need to create a new one
                        handle_tracker = HandleTrackerDeleter(self, st)
                        st.handle_tracker = handle_tracker
 
                        # we also need to reset the time that the status is supposed to be removed from the list
                        st.handle_destruction_time = rospy.Time.now()
 
                    # set the status of the goal to PREEMPTING or RECALLING as appropriate
                    # and check if the request should be passed on to the user
                    gh = ServerGoalHandle(st, self, handle_tracker)
                    if gh.set_cancel_requested():
                        # call the user's cancel callback on the relevant goal
                        self.cancel_callback(gh)
 
            # if the requested goal_id was not found, and it is non-zero, then we need to store the cancel request
            if goal_id.id != "" and not goal_id_found:
                tracker = StatusTracker(goal_id, GoalStatus.RECALLING)
                self.status_list.append(tracker)
                # start the timer for how long the status will live in the list without a goal handle to it
                tracker.handle_destruction_time = rospy.Time.now()
 
            # make sure to set last_cancel_ based on the stamp associated with this cancel request
            if goal_id.stamp > self.last_cancel:
                self.last_cancel = goal_id.stamp
 
    
    def internal_goal_callback(self, goal):
        with self.lock:
            # if we're not started... then we're not actually going to do anything
            if not self.started:
                return
 
            rospy.logdebug("The action server has received a new goal request")
 
            # we need to check if this goal already lives in the status list
            for st in self.status_list[:]:
                if goal.goal_id.id == st.status.goal_id.id:
                    rospy.logdebug("Goal %s was already in the status list with status %i" % (goal.goal_id.id, st.status.status))
                    # Goal could already be in recalling state if a cancel came in before the goal
                    if st.status.status == GoalStatus.RECALLING:
                        st.status.status = GoalStatus.RECALLED
                        self.publish_result(st.status, self.ActionResultType())
 
                    # if this is a request for a goal that has no active handles left,
                    # we'll bump how long it stays in the list
                    if st.handle_tracker is None:
                        st.handle_destruction_time = rospy.Time.now()
 
                    # make sure not to call any user callbacks or add duplicate status onto the list
                    return
 
            # if the goal is not in our list, we need to create a StatusTracker associated with this goal and push it on
            st = StatusTracker(None, None, goal)
            self.status_list.append(st)
 
            # we need to create a handle tracker for the incoming goal and update the StatusTracker
            handle_tracker = HandleTrackerDeleter(self, st)
 
            st.handle_tracker = handle_tracker
 
            # check if this goal has already been canceled based on its timestamp
            gh = ServerGoalHandle(st, self, handle_tracker)
            if goal.goal_id.stamp != rospy.Time() and goal.goal_id.stamp <= self.last_cancel:
                # if it has... just create a GoalHandle for it and setCanceled
                gh.set_canceled(None, "This goal handle was canceled by the action server because its timestamp is before the timestamp of the last cancel request")
            else:
                # now, we need to create a goal handle and call the user's callback
                self.goal_callback(gh)
 
    
    def publish_status_async(self, event):
        with self.lock:
            # we won't publish status unless we've been started
            if not self.started:
                return
            self.publish_status()
 
    
    def publish_status(self):
        with self.lock:
            # build a status array
            status_array = GoalStatusArray()
 
            # status_array.set_status_list_size(len(self.status_list));
 
            i = 0
            while i < len(self.status_list):
                st = self.status_list[i]
                # check if the item is due for deletion from the status list
                if st.handle_destruction_time != rospy.Time() and st.handle_destruction_time + self.status_list_timeout < rospy.Time.now():
                    rospy.logdebug("Item %s with destruction time of %.3f being removed from list.  Now = %.3f" %
                                   (st.status.goal_id, st.handle_destruction_time.to_sec(), rospy.Time.now().to_sec()))
                    del self.status_list[i]
                else:
                    status_array.status_list.append(st.status)
                    i += 1
 
            status_array.header.stamp = rospy.Time.now()
            if not rospy.is_shutdown():
                self.status_pub.publish(status_array)