Force render appended lines?

multi.py

#!/usr/bin/env python

import vtk
import Queue
from multiprocessing import Process, Queue
from datetime import datetime
import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print("MQTT connected with result code "+str(rc))
    client.subscribe("hello/world")

def on_message(client, userdata, msg):
    data = msg.payload.split(' ')
    x = float(data[0])
    y = float(data[1])
    z = float(data[2])
    point = [x, y, z]
    q.put(point)

def mqtt_client(q):
    client = mqtt.Client()
    client.on_connect = on_connect
    client.on_message = on_message
    client.connect("localhost", 1883, 60)
    print "Started mqtt client ..."
    client.loop_forever()

class vtkTimerCallback():
    def __init__(self, q, pts, lines):
        self.q = q
        self.timer_count = 0
        self.pts = pts
        self.lines = lines
        
    def execute(self, obj, event):
        if not self.q.empty():
            item = self.q.get()

            m = self.actor.GetMapper()
            linesPolyData = m.GetInput()
            l = linesPolyData.GetLines()
            number_of_lines = int(l.GetNumberOfCells())
            
            self.pts.InsertNextPoint(item)

            print item, number_of_lines, self.q.qsize()
            line2 = vtk.vtkLine()
            line2.GetPointIds().SetId(0, number_of_lines)
            line2.GetPointIds().SetId(1, number_of_lines + 1)
            self.lines.InsertNextCell(line2)

            linesPolyData.SetPoints(self.pts)
            linesPolyData.SetLines(self.lines)
        else:
            print "No data"

        if self.timer_count % 1 == 0:
            self.actor.GetProperty().SetColor(0,1,1)
        else:
            self.actor.GetPropert().SetColor(1,0,1)
        
        iren = obj
        iren.GetRenderWindow().Render()
        self.timer_count += 1
    
def vtk_main(q):
    origin = [0.0, 0.0, 0.0]
    p0 = [1.0, 0.0, 0.0]
    p1 = [0.0, 1.0, 0.0]

    pts = vtk.vtkPoints()
    pts.InsertNextPoint(origin)
    pts.InsertNextPoint(p0)
    pts.InsertNextPoint(p1)
 
    line0 = vtk.vtkLine()
    line0.GetPointIds().SetId(0,0) # the second 0 is the index of the Origin in the vtkPoints
    line0.GetPointIds().SetId(1,1) # the second 1 is the index of P0 in the vtkPoints

    line1 = vtk.vtkLine()
    line1.GetPointIds().SetId(0,0) # the second 0 is the index of the Origin in the vtkPoints
    line1.GetPointIds().SetId(1,2) # 2 is the index of P1 in the vtkPoints

    lines = vtk.vtkCellArray()
    lines.InsertNextCell(line0)
    lines.InsertNextCell(line1)
 
    linesPolyData = vtk.vtkPolyData()

    linesPolyData.SetPoints(pts)
    linesPolyData.SetLines(lines)

    mapper = vtk.vtkPolyDataMapper()
    mapper.SetInputData(linesPolyData)
 
    actor = vtk.vtkActor()
    actor.SetMapper(mapper)
 
    renderer = vtk.vtkRenderer()
    renderWindow = vtk.vtkRenderWindow()
    renderWindow.AddRenderer(renderer)
    renderWindowInteractor = vtk.vtkRenderWindowInteractor()
    renderWindowInteractor.SetRenderWindow(renderWindow)
    renderer.AddActor(actor)
 
    renderWindow.Render()

    cb = vtkTimerCallback(q, pts, lines)
    cb.actor = actor
    renderWindowInteractor.AddObserver('TimerEvent', cb.execute)
    timerId = renderWindowInteractor.CreateRepeatingTimer(3000);

    renderWindowInteractor.Start()

if __name__ == '__main__':
    q = Queue()
    mqtt_client = Process(name='mqtt', target=mqtt_client, args=(q,))
    vtk_client = Process(name='vtk', target=vtk_main, args=(q,))

    mqtt_client.start()
    vtk_client.start()