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Hi,
I'm working on autonomous quadcopter system and I'm using ROS for my algorithms. What I would like to achieve is to create some watchdogs monitoring all my ROS nodes. I also want it to be able to restart node if it detects it's shutdown (for whatever reason).
But I'm quite lost. Can someone give me an advice or perhaps reference to existing code which does exactly this?
Thank you.
You could use a bond:
#! /usr/bin/python
import rospy
from bondpy import bondpy
def formed():
print "We got a bond"
def broken():
print "SOMEONE DIED"
rospy.init_node("A", anonymous=True)
b = bondpy.Bond("heartbeat_topic_name","bond_name", on_broken=broken, on_formed=formed)
b.start()
if not b.wait_until_formed():
raise Exception('Bond could not be formed')
rospy.spin()
Just start this node twice, wait for the bond to be established and kill one of the nodes. After a short timeout (4 seconds) the other node will notice the missing partner. With this method, you don't need to poll rosnode list or even know the name of the other node, you just have to use the same topic and bond_name to establish the connection and have a callback triggered as soon as one node does not send its heartbeat anymore.
Interesting answer! Didn't know this technique! But how would use bonding with pre-existing nodes?
To be honest, this code was the first time I used a bond :) But yeah, you can bond exactly two processes, so you will have N bonds.
@gstavrinos: you have to change the node, so it won't work with existing nodes.
I know it's a bit late to answer this but I found node_alive to be very helpful in getting the state of the nodes in the system. It publishes a DiagnosticArray on /diagnostics topic with the information about all the nodes visible to rosmaster and their status.
When I want to do something like that, I mainly use two techniques:
e.g.
<node pkg="rospy_tutorials" type="listener" name="listener" respawn="true" />
You can check the official roslaunch wiki page for more info.
e.g.
nodes = os.popen("rosnode list").readlines()
for node in nodes:
# Make your tests here
Not all nodes are removed from the list when they die, especially if they crash (that's the reason why there is 'rosnode cleanup') A node that is listed in 'rosnode list' does not have to be alive!
Asked: 2017-04-05 04:41:12 -0600
Seen: 3,970 times
Last updated: Oct 04 '18
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