Publish when Subscribers have finished their loop.

edit

I have a ros build that is working quite well. I take a DataFrame of coordinates (x, y, z) and covert them, one at a time, to a list of 4 angles. That list is then published to a single topic and 4 subscriber nodes each take their respective angle from that list. Once the subscribers receive their angles they call a function to move a motor to that angle.

The issue that I'm having (less of an issue and more of a desire) is that I would like the 4 nodes to tell the publisher when they are done and once all four say they are done then the publisher will send the next set of angles. Otherwise I have to allow for the longest possible rotation time even if the operation will take a fraction of that.

I have looked into both services and a publisher/subscriber in one system and can't seem to find a reasonable solution.

I have attached a copy of my publisher and one of my subscribers. Any suggestions?

PUBLISHER:

def motorMaster():
'''
The Master Node defined as a function. Using a multiarray message, the 4 angles are calculated
by the functions brought in from motorControls and then published to a single topic. Each motor
pulls its respective command from that multiarray.
'''
angPub = Publisher('motAngs', Float32MultiArray, queue_size=10)
init_node('master', anonymous=True)
rate = Rate(.5)
while not is_shutdown():
    for i in dataFrame.values:
        angles = genAngles(list(i))
        loginfo(angles)
        angPub.publish(data=angles)
        rate.sleep()
if __name__ == '__main__':
    try:
        motorMaster()
    except ROSInterruptException:
        pass

SUBSCRIBER:

def baseAngCall(data):
'''
Logs the angle calculated by the master and feeds it to the base motor.
'''
loginfo(data.data[0])
baseAng = data.data[0]
baseMotor.moveToAngle(baseAng)

def baseMotNode():
    '''
    Subscriber Node for the base motor.
    '''
    init_node('baseMotor', anonymous=True)
    Subscriber('motAngs', Float32MultiArray, baseAngCall)
    spin()

if __name__ == '__main__':
    gpioInit(11, 12)
    baseMotNode()

NOTE: Many of the functions used are hosted in another python file used as a module to keep the nodes clean.