Flask application dies after first POST request

asked 2019-01-02 04:22:48 -0500

stevemartin gravatar image

I am using Flask application to accept user goals for my robot. The problem occurs when I call the service. Here is the code:

from flask import Flask, jsonify, request
from flask_pymongo import PyMongo
import json
import rospy
from path_caller import PathCaller
from tf import TransformListener
from geometry_msgs.msg import PoseStamped
from nav_msgs.srv import GetPlan

app = Flask(__name__)
#app.config['MONGO_DBNAME'] = 'prge'
app.config["MONGO_URI"] = "mongodb://user:pass@ds04505.mlab.com:29345/prge"

mongo = PyMongo(app)

@App.route('/goal', methods=['POST'])
def add_goal():
    goal = mongo.db.goal
    position = request.json['position']
    orientation = request.json['orientation']
    goal_id = goal.insert({'position' : position, 'orientation' : orientation})
    new_goal = goal.find_one({'_id' : goal_id})
    output = {'position' : new_goal['position'], 'orientation' : new_goal['orientation']}
    position_x = json.loads(position['x'])
    position_y = json.loads(position['y'])
    #call_service(position_x, position_y)

    return jsonify(output)

def create_pose_stamped(x,y,th_x,th_y):
    pose = PoseStamped()
    pose.header.stamp = rospy.Time.now()
    pose.header.frame_id = "map"
    pose.pose.position.x = x
    pose.pose.position.y = y
    pose.pose.position.z = 0.0
    pose.pose.orientation.x = 0
    pose.pose.orientation.y = 0
    pose.pose.orientation.z = th_x
    pose.pose.orientation.w = th_y
    return pose

def get_start_position():
    tf = TransformListener()
    if tf.frameExists("base_footprint") and tf.frameExists("odom"):
        print "Frames exist"
        t = tf.getLatestCommonTime("/base_link", "/map")
        p,q = tf.lookupTransform("/odom", "/base_footprint", t)
        print p
    x = 1
    y = 5.9
    z = 0
    w = 1
    return [x,y,z,w]

def call_service(x,y):
    start_vars = get_start_position()
    start = create_pose_stamped(start_vars[0], start_vars[1], start_vars[2], start_vars[3])
    end = create_pose_stamped(x,y,0,1.0)
    rospy.loginfo("The start x: %.2f, y: %.2f, the end x: %.2f, y: %.2f", start.pose.position.x, start.pose.position.y, end.pose.position.x, end.pose.position.y)
    gp_service = rospy.ServiceProxy('/move_base/make_plan', GetPlan)
        response = gp_service(start, end, 1.0)
        rospy.loginfo("The path is %s", response.plan.poses)
    except rospy.ServiceException as e:
        print "Service did not process request " + str(e)

if __name__ == '__main__':

After I POST a goal first time, everything works as expected. But when I POST the goal second time I get this error:

Exception happened during processing of request from ('', 53198)
Traceback (most recent call last):
  File "/usr/lib/python2.7/SocketServer.py", line 596, in process_request_thread
    self.finish_request(request, client_address)
  File "/usr/lib/python2.7/SocketServer.py", line 331, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python2.7/SocketServer.py", line 652, in __init__
  File "/home/ikhsanov/.local/lib/python2.7/site-packages/werkzeug/serving.py", line 293, in handle
    rv = BaseHTTPRequestHandler.handle(self)
  File "/usr/lib/python2.7/BaseHTTPServer.py", line 340, in handle
  File "/home/ikhsanov/.local/lib/python2.7/site-packages/werkzeug/serving.py", line 324, in handle_one_request
    self.raw_requestline = self.rfile.readline()
IOError: [Errno 11] Resource temporarily unavailable

This is definately due to the service call as if I comment out the service call, everything works as expected. Also, when I call it for ... (more)

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When I have added time.sleep(1) right after the tf declaration, the problem has been solved. No idea why.

stevemartin gravatar image stevemartin  ( 2019-01-03 07:17:05 -0500 )edit

I don't know anything about flask I'm afraid. Although looking at your get_start_position function, it will return the default value (which is an invalid rotation quaternion) always since there is not return inside the if statement. Don't know if that's related.

PeteBlackerThe3rd gravatar image PeteBlackerThe3rd  ( 2019-01-03 07:41:53 -0500 )edit