Volttron throws an Attribute error when attempting to publish

Question

I am combining Scapy with Volttron and I want to publish to a topic when a packet comes in and has certain features. However, I keep running into this error:

Traceback (most recent call last): File "sniff.py", line 373, in sys.exit(main()) File "sniff.py", line 342, in main utils.vip_main(sniffer, version=version) File "/home/jenny/workspace/volttron/volttron/platform/agent/utils.py",

line 314, in vip_main version=version, **kwargs) File "sniff.py", line 336, in sniffer Sniffer(**kwargs) File "sniff.py", line 138, in init self.vip.pubsub.publish('pubsub', "some/topic", message="blah")
File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/subsystems/pubsub.py",

line 602, in publish self._save_parameters(result.ident, **kwargs)
File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/subsystems/pubsub.py", line 706, in _save_parameters event = self.core().schedule(end_time, self._cancel_event, result_id)
File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/core.py", line 409, in schedule self._schedule_callback(deadline, event) File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/core.py", line 417, in _schedule_callback self._schedule_event.set()

AttributeError: 'NoneType' object has no attribute 'set'

The closest to a solution I found is here RPC crashes with AttributeError: 'NoneType' object has no attribute 'call'. However, I notice they aren't exactly the same issue and so there isn't much surprise when I tried the solution offered there and it didn't work for me.

My code looks like this:

def sniffer(config_path, **kwargs):

    ''' Initializations '''
    global pkt_counter
    global IP_counter
    # Defined other parameters here

    class Sniffer(Agent):
        def __init__(self, **kwargs):
            super(Sniffer, self).__init__(**kwargs)
            # I am just testing the publish function here
            self.vip.pubsub.publish('pubsub', "some/topic", message="blah")
            sniff(count=0, iface=conf.iface, prn = self.pkt_action, store=0)


        def pkt_action(self, pkt):
            #Process every packet, updates values and rises and alert if necessary 
            # some checks are run here and later a publish is called

Can someone please let me know what I'm doing wrong?

Edit: I didn't add that I want to run this script as I would a simple python script on the terminal (eg. python somescript.py): no installation. The reason I'm trying to do this is that I get an error when I install the agent and start it. The platform doesn't allow Scapy to create and connect to sockets.

score 0 · Accepted Answer · edited Jun 20 '20 at 09:12

0

You are attempting to use the vip module from in a context that isn't expected. The agent's lifecycle doesn't actually start executing until the start agent or configure events are triggered. Try to put the publish within those contexts.

The following excerpt is from the VOLTTRON readthedocs site located: https://volttron.readthedocs.io/en/develop/devguides/agent_development/Agent-Development-Cheatsheet.html#agent-lifecycle-events

Core Agent Functionality These tools volttron.platform.vip.agent module. Try importing

Agent Lifecycle Events Each agent has four events that are triggered at different stages of its life. These > are onsetup, onstart, onstop, and onfinish. Registering callbacks to these events are commonplace in agent development, with onstart being the most frequently used.

The easiest way to register a callback is with a function decorator:


@Core.receiver('onstart')
def function(self, sender, **kwargs):
    function_body

edited Jun 20 '20 at 09:12

Community

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answered Aug 27 '19 at 01:22

Craig

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Thanks for your help Craig. I just noticed I didn't add that I wanted to call this script from the console without installing as you would do the Matlab Standalone agent in windows. When I add Core.receiver('onstart'), I don't get the error but it connects very briefly to the platform and then disconnects without outputting anything at all. – O'Jhene Aug 27 '19 at 13:44
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Thanks a ton Craig! I redid it a couple of times and it failed. Finally I added authentication credentials as you suggested here https://stackoverflow.com/questions/42013280/volttron-platform-vip-agent-core-error-possible-conflicting-identity, put in the 'onstart' method as you suggested and it worked! Previously, I was adding it the wrong way. Cheers! – O'Jhene Aug 28 '19 at 16:11

Volttron throws an Attribute error when attempting to publish

1 Answers1