Working with Custom Actions

MindMeld 4.3 provides the ability for external applications to integrate custom dialogue management logic with MindMeld applications.

Why Custom Actions?

Suppose that a team is working to build a MindMeld application and integrate it the rest of their microservices. Since the microservices are written in Java, the developers want to reuse as much logic as possible. Since the MindMeld application is in Python, they would have to re-implement their Java code to Python code.

With Custom Actions, the developers can now shift the responsibility of fulfilling business logic to services that are outside of MindMeld applications, and these services can be implemented in any language. The developers can specify the exact conditions (for example, matching a certain domain or intent) to execute the custom actions and the MindMeld application will interact with the custom action servers through http(s) requests.

OpenAPI Specification for client-server interaction

Our client – server protocol is documented here. For easy viewing you can check out Swagger UI, which can also help to render OpenAPI protocol into client and server stubs in a variety of languages.

Each request to the Custom Action Server includes two fields: request and responder. The request field encapsulates information from the Request object (text, NLP information, etc.) and the responder field the Responder object (directives, frame, slots, params).

In a normal MindMeld application, each object is passed into the application handler for processing.

def handle_intent(request, responder):
    # normal MindMeld application logic goes here

In an analogous process to @app.handle, when we invoke the custom action, we are serializing the request and responder and passing them into the body of the http request to the server. In the response, we simply expect it to contain all the fields of the Responder object which will be deserialized and processed before returning to the end client.

Configure Custom Actions for your MindMeld application

You can specify custom action configuration in with the url field:


Currently MindMeld also supports SSL encryption by specifying the following fields in the CUSTOM_ACTION_CONFIG: cert, public_key and private_key. Each field is the path to the local location of the certificate, public and private key.

In your Dialogue Manager, you can access the application's custom action config by referencing the application's property app.custom_action_config.

A Sample Custom Action Server

To understand the behavior of Custom Actions, let's take a look at example of a Custom Action Server. We have added a sample server for Python 3.6+ in the github directory under examples/custom_action/example_server. This server is adapted from the sample server that is auto-generated from our OpenAPI protocol using the Swagger Online Editor.

To setup the sample server, you can run the following command in the terminal:

pip install mindmeld[examples]

# optionally, to view the MindMeld API in the local browser:
pip install "connexion[swagger-ui]"

git clone

cd mindmeld/examples/custom_action/example_server

# to run the server
python -m swagger_server

The server will run locally at address

In this example, the server simply returns a reply directive for each action request that includes the name of the action.

import connexion

from import Data
from ..models.responder import Responder
from ..models.directive import Directive

def invoke_action(body):
    """Invoke an action

    This API accepts the serialized MindMeld Request and Responder and returns a serialized Responder

    :param body:
    :type body: dict | bytes

    :rtype: Responder
    directives = []
    if connexion.request.is_json:
        data = Data.from_dict(body)

        msg = "Invoking {action} on custom server.".format(action=data.action)

        reply = Directive(name="reply", payload={"text": msg}, type="view")
    responder = Responder(directives=directives, frame={})
    return responder

To test the server, you can run the following code snippet:

from mindmeld.components.custom_action import CustomAction
action_config = {'url': 'http://localhost:8080/action'}

action = CustomAction(name='action_call_people', config=action_config)
from mindmeld.components.request import Request
from mindmeld.components.dialogue import DialogueResponder

# should get 400 since the request fields are missing
action.invoke(Request(), DialogueResponder())

# synchronous case
request = Request(text='some text', domain='some domain', intent='some intent')
responder = DialogueResponder()

# we should see a successful request and one reply directive
action.invoke(request, responder)
print('Directives:', responder.directives)

You can explore the implementation of the Request and Responder data objects in our sample server to return different fields of MindMeld.

Using Custom Actions with MindMeld applications

Add a call to a custom action as follows:

app = Application(__name__)
app.custom_action(intent='deny', action='action_restart')

In the above example, we are specifying that when deny intent is reached, the application should make a call for action_restart to the URL specified in CUSTOM_ACTION_CONFIG.

In our response, we should see one reply directive with the message: Invoking action_restart on custom server.

If your application is asynchronous, you can specify the custom action to be executed asynchronously with the async_mode flag.

app = Application(__name__, async_mode=True)
app.custom_action(intent='deny', action='action_restart', async_mode=True)

If there are more than one custom action server, you can also choose to specify the server by passing the custom action config directly into the application.

config = {"url": ""}
app.custom_action(intent='deny', action='action_restart', config=config)

If you want to execute a sequence of custom actions, you can pass the list of actions into the actions field.

app.custom_action(intent='ask_help', actions=['action_help', 'action_restart'])

In our response, we should see two replies: Invoking action_help on custom server, Invoking action_restart on custom server.

The default behavior for executing a sequence of custom actions is to merge all of their fields in the final responder. If we set the merge flag to be False, we will only keep the result of the last action.

app.custom_action(intent='ask_help', actions=['action_help', 'action_restart'], merge=False)

Here, in the final response, we will see only one reply: "Invoking action_restart on custom server".

Calling Individual Custom Actions inside a MindMeld application

You can invoke individual custom actions by calling the CustomAction object directly. You can access the current application's custom action configuration from the application's property app.custom_action_config.

def action_check_out(request, responder):
    from mindmeld.components import CustomAction
    CustomAction(name='action_restart', config=app.custom_action_config).invoke(request, responder)

Alternatively, you can define a new application's config and pass it directly into the CustomAction.

config = {"url": ""}
CustomAction(name='action_restart', config=config).invoke(request, responder)

The advantage of invoking a custom action manually is that you can further refine and process the results from the custom actions. Here the resulting fields are merged into the responder object.

Similarly to the custom_action handler, we can pass the merge flag into the CustomAction object to set its behavior for handling the fields of the returned Responder.

def action_check_out(request, responder):
    CustomAction(name='action_restart', config=config, merge=True).invoke(request, responder)

You can also invoke the CustomAction asynchronously as well:

async def action_check_out(request, responder):
    await CustomAction(name='action_restart', config=config).invoke(request, responder, async_mode=True)

We can pipe multiple custom actions easily in a sequence and mix this sequence with any operation by the responder.

def handle_ask_help(request, responder):
    responder.reply('I can help you')
    CustomAction(name='action_help', config=config).invoke(request, responder)
    CustomAction(name='action_restart', config=config).invoke(request, responder)

In the example above, first we choose to add a reply first, and then invoke two custom actions in sequence.

In the final result, we should see three replies: I can help you, Invoking action_help on custom server, Invoking action_restart on custom server.

Instead of calling individual CustomAction in sequence, you can also use the CustomActionSequence class.

def handle_ask_help(request, responder):
    from mindmeld.components import CustomActionSequence

    responder.reply('I can help you')
    CustomActionSequence(actions=['action_help', 'action_restart'], config=config).invoke(request, responder)

For your convenience, we also provide helper functions (invoke_custom_action, invoke_custom_action_async) which wrap around the CustomAction class.

def action_check_out(request, responder):
    from mindmeld.components import invoke_custom_action
    invoke_custom_action('action_restart', config, request, responder)