Agent Creation Walkthrough

The VOLTTRON platfrom now has utilities to speed the creation and installation of new agents. To use these utilities the VOLTTRON environment must be activated.

From the project directory, activate the VOLTTRON environment with:

. env/bin/activate

Create Agent Code

Run the following command to start the Agent Creation Wizard:

vpkg init TestAgent tester

TestAgent is the directory that the agent code will be placed in. The directory must not exist when the command is run.

tester is the name of the agent module created by wizard.

The Wizard will promt for the following information:

Agent version number: [0.1]: 0.5
Agent author: []: VOLTTRON Team
Author's email address: []:
Agent homepage: []:
Short description of the agent: []: Agent development tutorial.

Once the last question is answered the following will print to the console:

2018-08-02 12:20:56,604 () volttron.platform.packaging INFO: Creating TestAgent
2018-08-02 12:20:56,604 () volttron.platform.packaging INFO: Creating TestAgent/tester
2018-08-02 12:20:56,604 () volttron.platform.packaging INFO: Creating TestAgent/
2018-08-02 12:20:56,604 () volttron.platform.packaging INFO: Creating TestAgent/config
2018-08-02 12:20:56,604 () volttron.platform.packaging INFO: Creating TestAgent/tester/
2018-08-02 12:20:56,604 () volttron.platform.packaging INFO: Creating TestAgent/tester/

The TestAgent directory is created with the new Agent inside.

Agent Directory

At this point, the contents of the TestAgent directory should look like:

├── config
└── tester

Examine the Agent Code

The resulting code is well documented with comments and documentation strings. It gives examples of how to do common tasks in VOLTTRON Agents.

The main agent code is found in tester/

Here we will cover the highlights.

Parse Packaged Configuration and Create Agent Instance

The code to parse a configuration file packaged and installed with the agent is found in the tester function:

def tester(config_path, **kwargs):
    """Parses the Agent configuration and returns an instance of
    the agent created using that configuration.

    :param config_path: Path to a configuration file.

    :type config_path: str
    :returns: Tester
    :rtype: Tester
        config = utils.load_config(config_path)
    except StandardError:
        config = {}

    if not config:"Using Agent defaults for starting configuration.")

    setting1 = int(config.get('setting1', 1))
    setting2 = config.get('setting2', "some/random/topic")

    return Tester(setting1,

The configuration is parsed with the utils.load_config function and the results are stored in the config variable.

An instance of the Agent is created from the parsed values and is returned.

Initialization and Configuration Store Support

The configuration store is a powerful feature introduced in VOLTTRON 4. The agent template provides a simple example of setting up default configuration store values and setting up a configuration handler.

class Tester(Agent):
    Document agent constructor here.

    def __init__(self, setting1=1, setting2="some/random/topic",
        super(Tester, self).__init__(**kwargs)
        _log.debug("vip_identity: " + self.core.identity)

        self.setting1 = setting1
        self.setting2 = setting2

        self.default_config = {"setting1": setting1,
                               "setting2": setting2}

        #Set a default configuration to ensure that self.configure is called immediately to setup
        #the agent."config", self.default_config)
        #Hook self.configure up to changes to the configuration file "config"., actions=["NEW", "UPDATE"], pattern="config")

    def configure(self, config_name, action, contents):
        Called after the Agent has connected to the message bus. If a configuration exists at startup
        this will be called before onstart.

        Is called every time the configuration in the store changes.
        config = self.default_config.copy()

        _log.debug("Configuring Agent")

            setting1 = int(config["setting1"])
            setting2 = str(config["setting2"])
        except ValueError as e:
            _log.error("ERROR PROCESSING CONFIGURATION: {}".format(e))

        self.setting1 = setting1
        self.setting2 = setting2


Values in the default config can be built into the agent or come from the packaged configuration file. The subscribe method tells our agent which function to call whenever there is a new or updated config file. For more information on using the configuration store see Agent Configuration Store

_create_subscriptions (convered in the next section) will use the value in self.setting2 to create a new subscription.

Setting up a Subscription

The Agent creates a subscription using the value of self.setting2 in the method _create_subscription. The messages for this subscription hare handeled with the _handle_publish method:

def _create_subscriptions(self, topic):
    #Unsubscribe from everything."pubsub", None, None)'pubsub',

def _handle_publish(self, peer, sender, bus, topic, headers,

Agent Lifecycle Events

Methods may be setup to be called at agent startup and shudown:

def onstart(self, sender, **kwargs):
    This is method is called once the Agent has successfully connected to the platform.
    This is a good place to setup subscriptions if they are not dynamic or
    do any other startup activities that require a connection to the message bus.
    Called after any configurations methods that are called at startup.

    Usually not needed if using the configuration store.
    #Example publish to pubsub'pubsub', "some/random/topic", message="HI!")

    #Exmaple RPC call"some_agent", "some_method", arg1, arg2)

def onstop(self, sender, **kwargs):
    This method is called when the Agent is about to shutdown, but before it disconnects from
    the message bus.

As the comment mentions. With the new configuration store feature onstart methods are mostly unneeded. However this code does include an example of how to do a Remote Proceedure Call to another agent.

Agent Remote Proceedure Calls

An agent may receive commands from other agents via a Remote Proceedure Call or RPC for short. This is done with the @RPC.export decorattor:

def rpc_method(self, arg1, arg2, kwarg1=None, kwarg2=None):
    RPC method

    May be called from another agent via """
    return self.setting1 + arg1 - arg2

Packaging Configuration

The wizard will automatically create a file. This file sets up the name, version, required packages, method to execute, etc. for the agent based on your answers to the wizard. The packaging process will also use this information to name the resulting file.

from setuptools import setup, find_packages

MAIN_MODULE = 'agent'

# Find the agent package that contains the main module
packages = find_packages('.')
agent_package = 'tester'

# Find the version number from the main module
agent_module = agent_package + '.' + MAIN_MODULE
_temp = __import__(agent_module, globals(), locals(), ['__version__'], -1)
__version__ = _temp.__version__

# Setup
    name=agent_package + 'agent',
    description="Agent development tutorial.",
    author="VOLTTRON Team",
        'setuptools.installation': [
            'eggsecutable = ' + agent_module + ':main',

Launch Configuration

In TestAgent, the wizard will automatically create a file called “config”. It contains configuration information for the agent. This file contains examples every datatype supported by the configuration system:

  # VOLTTRON config files are JSON with support for python style comments.
  "setting1": 2, #Integers
  "setting2": "some/random/topic2", #strings
  "setting3": true, #Booleans: remember that in JSON true and false are not capitalized.
  "setting4": false,
  "setting5": 5.1, #Floating point numbers.
  "setting6": [1,2,3,4], # Lists
  "setting7": {"setting7a": "a", "setting7b": "b"} #Objects

Packaging and Installing the Agent

To install the agent the platform must be running. Start the platform with the command:

volttron -l volttron.log -vv&

Now we must install it into the platform. Use the following command to install it and add a tag for easily referring to the agent. From the project directory, run the following command:

python scripts/ -s TestAgent/ -c TestAgent/config -t testagent

To verify it has been installed, use the following command: volttron-ctl list

This will result in output similar to the following:

  AGENT                    IDENTITY           TAG       STATUS          HEALTH
e testeragent-0.5          testeragent-0.5_1  testagent

Where the number or letter is the unique portion of the full uuid for the agent. AGENT is the “name” of the agent based on the contents of its class name and the version in its IDENTITY is the agent’s identity in the platform. This is automatically assigned based on class name and instance number. This agent’s ID is _1 because it is the first instance. TAG is the name we assigned in the command above. HEALTH is the current health of the agent as reported by the agents health subsystem.

When using lifecycle commands on agents, they can be referred to be UUID (default) or AGENT (name) or TAG.

Testing the Agent

From the Command Line

To test the agent, we will start the platform (if not already running), launch the agent, and check the log file.

  • With the VOLTTRON environment activated, start the platform by running (if needed):

volttron -l volttron.log -vv&

  • Launch the agent by <uuid> using the result of the list command:

vctl start <uuid>

  • Launch the agent by name with:

vctl start --name testeragent-0.1

  • Launch the agent by tag with:

volttron-ctl start --tag testagent

volttron-ctl status

  • Start the ListenerAgent as in Building VOLTTRON
  • Check the log file for messages indicating the TestAgent is receiving the ListenerAgents messages:

Automated Test cases and documentation

Before contributing a new agent to the VOLTTRON source code repository, please consider adding two other essential elements.

  1. Integration and unit test cases

2. README file that includes details of pre-requisite software, agent setup details (such as setting up databases, permissions, etc.)and sample configuration

VOLTTRON uses py.test as a framework for executing tests. All unit tests should be based on py.test framework. py.test is not installed with the distribution by default. To install py.test and it’s dependencies execute the following:

python --testing


There are other options for different agent requirements. To see all of the options use:

python --help

in the Extra Package Options section.

To run a single test module, use the command

pytest <>

To run all of the tests in the volttron repository execute the following in the root directory using an activated command prompt: