Creating a Custom Logger as a Jovo Plugin

by Kaan Kilic on Sep 17, 2018

Tutorial: Using Google Spreadsheets for your Alexa Skills and Google Actions

Learn how to write your own Jovo Plugin. In this tutorial, we are creating a custom logger plugin for voice apps built with the Jovo Framework.

You can find the full code example of this tutorial here: jovo-templates/tutorials/plugin.

Or download it using the Jovo CLI:

Introduction to Jovo Plugins

We added the Jovo Plugin feature in order to allow our users to customize the framework to their needs as well as to build features, which other members of our community can benefit from.

Plugins allow you to easily extend the Jovo Framework without having to mess with its core code and architecture. You can, for example, integrate your own analytics API or create a custom logger.

See example plugins here.

How Jovo Plugins Work

The plugins work with middlewares, which all combined handle the complete request execution. As soon as the execution reaches the middleware your plugin is connected to, it will run your specified function. Learn more about the Jovo framework architecture here.

Middleware Description
setup First initialization of app object with first incoming request. Is executed once as long as app is alive
request Raw JSON request from platform gets processed. Can be used for authentication middlewares.
platform.init Determines which platform (e.g. Alexa, GoogleAssistant) sent the request. Initialization of abstracted jovo (this) object.
platform.nlu' Natural language understanding (NLU) information gets extracted for built-in NLUs (e.g. Alexa). Intents and inputs are set.
nlu Request gets routed through external NLU (e.g. Dialogflow standalone). Intents and inputs are set.
user.load Initialization of user object. User data is retrieved from database.
router Request and NLU data (intent, input, state) is passed to router. intentMap and inputMap are executed. Handler path is generated.
handler Handler logic is executed. Output object is created and finalized. User gets finalized, DB operations.
platform.output Platform response JSON gets created from output object.
response Response gets sent back to platform.
fail Errors get handled if applicable.

Creating a Custom Logger

Since plugins feature is tailored for more advanced users, I will skip the creation of a Jovo project and jump right into the code example. The plugin we're going to create will be a simple logger to track Google's Default Fallback Intent.

The plugin I will show you here will be very small and written in JavaScript. To see a more fleshed out example check out the jovo-integrations folder, which are all plugins as well:

To build our own plugin we have to create a class:

Inside that class we will add a constructor, which will be empty for now:

Next up is the core part of the plugin. The install() method is the place, where you connect to the middlewares:

Save Response

The first middleware we want to connect to, is the platform.output middleware, to log our app's response as well as the state prior to the utterance of our user, which triggered the Default Fallback Intent. Every time the request execution gets to the platform.output middleware, our saveOutput() function will be executed as well.

Our function will have a single input, the handleRequest object, which every function connected to a middleware will get. It has the following interface:

We will need the jovo object, which is the same object we access using this inside we handler.

The first thing we will check for is, if the request came from the GoogleAction platform.

After that we get both the speech and, if it exists, the reprompt string and delete their speak tags:

After that we also save the state and add everything to the output string, which we will add to the constructor:

That's all we need to do here. Next up, is to check the incoming requests for the Default Fallback Intent and log our saved output with the user's utterance.

Log the Default Fallback Intent

To do that we connect our plugin to the platform.nlu middleware, which will execute the log() function.

Inside the log() function we check for the platform, the Default Fallback Intent,add the user's utterance to the output, log the whole string and reset it back to and empty string.

At the end our plugin looks like this:

Enable Plugin

Last but not least, we add the plugin to our app using the app.use() function, which we can find at the top of our ./src/app.js file:

You can test the plugin either locally, where it will we logged to your console, or on Lambda, which stores the logs on Cloudwatch. Here's an example how the logs might look like:

We at Jovo are really excited to see, which kind of plugins our community comes up with. By the way, the first ever Jovo plugin was created by Cellular.

Any questions? Please let us know in the comments below 👇. You can also reach us on Twitter or Slack.

Kaan Kilic

Technical Content Marketing Associate at Jovo

Comments and Questions

Any specific questions? Just drop them below or join the Jovo Community Forum.

Join Our Newsletter

Be the first to get our free tutorials, courses, and other resources for voice app developers.