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Use the API in Atlas App Services to Analyze Sentiment

Now you want to start linking the Natural Language API with Atlas App Services so you can use it from within our app. Before starting this section, make sure you have the Atlas App Services Bakery application open in your browser.

Create a Value for the NL API URL and Key

You want to store some values from Google Cloud, including your new API key, inside App Services values, so they can be accessed from within multiple services, including Functions and Triggers.

  1. Select Values from the left menu under the Build heading.

  2. Click Create New Value.

  3. Enter the following details in the form that appears:

    • Give Your Value a Name: gcpAPIKey.
    • Choose a Type: Secret.
    • Add Content: Insert your API key you copied from Google Cloud in the last section.
    • Click Save Value.
  4. By its very nature, a secret is a secret. So in order to access it, you need to define an additional value that points to our secret that you can then call from our function later. Click Create a New Value and add the following:

    • Give Your Value a Name: gcpAPIKey.
    • Choose a Type: Value.
    • Add Content: Link to Secret.
    • gcpAPIKey.
    • Click Save Value.
  5. You now need to create a second Value, so click Create New Value in the top right and add the following:

  6. Click Review & Deploy Draft to apply the changes.

Create Atlas Functions to Analyze Sentiment

Now that you have the values saved and available to reference, it’s time to write the functions that will fetch the new document and also call the Natural Language API.

  1. Select Functions from the left and click Create New Function.

  2. Enter the following details:

    • Name: analyzeCommentSentiment.
    • Authentication: System.
    • Leave the rest as default and click Save Draft.
  3. This will open the Function Editor, so replace the default code with the following:

    exports = async function(comment) {
    const URL = context.values.get("gcpSentimentAnalyzeURL");
    const gcpAPIKey = context.values.get("gcpAPIKey");

    const response = await{
    url: `${URL}?key=${gcpAPIKey}`,
    body: {
    "document": {
    "type": "PLAIN_TEXT",
    "language": "en-US",
    "content": comment
    encodeBodyAsJSON: true

    // The response body is a BSON.Binary object. Parse it and return.
    return JSON.parse(response.body.text());
  4. Click Save Draft and then Review Draft & Deploy again to share our changes.

    This function is fairly simple. It takes in a comment object, then assigns the values you saved earlier in Values as local variables. It then sends our comment to the API via a POST request, parses the response to text, and returns it.

  5. Click Create New Function from inside Functions again.

  6. Enter the following details:

    • Name: getCommentAndAnalyzeSentiment.
    • Authentication: System.
    • Leave the rest as default and click Save Draft.
  7. In the Function Editor, replace the existing code with the following:

    exports = async function (changeEvent) {
    const commentDocument = changeEvent.fullDocument;
    const sentiment = await context.functions.execute("analyzeCommentSentiment", commentDocument.text);

    const commentsCollection ="mongodb-atlas").db("Bakery").collection("comments");
    await commentsCollection.updateOne(
    _id: commentDocument._id
    }, {
    $set: { sentiment }

Hit Save Draft to persist your changes.

This function gets the document from the changeEvent and then calls the analyzeCommentSentiment function, passing the comment text as an argument. You then call another MongoDB Query API function, updateOne, which will update our existing document with a new sentiment field with the details you get back from the Natural Language API.

Set up a Trigger to Run the Function on a New Comment

In the last section, you set up two functions to help us call out to the Natural Language API, but now you want to create a trigger that can be called when a new comment is created, calling out to that function to request the analysis.

  1. Select Triggers from the left side.

  2. Click Add a Trigger and add the following before hitting Save:

    • Trigger Type: Database
    • Name: getCommentAndAnalyzeSentiment
    • Cluster Name: Workshop-Bakery
    • Database Name: Bakery
    • Collection Name: comments
    • Operation Type: Insert
    • Full Document: Enabled
    • Select An Event Type: Function
    • Function: getCommentAndAnalyzeSentiment
  3. Click Review Draft & Deploy to deploy the changes.

Testing it all together

Woo! You now have all the pieces in place, so it’s time to start seeing your hard work in action.

  1. Go back to your StackBlitz tab which is still running the bakery application.

  2. Click into one of your existing cakes and add a comment. You will see it added to the page under the comments section.

  3. Head back to Atlas and click Browse Collections like you learned about in the first chapter when you inserted your first documents.

  4. Click into the comments collection inside the Bakery database and have a look at the document for the comment you just wrote.

    • You will see a new field called sentiment with the Object type.
    • Expand this object and then expand the documentSentiment field (also an object), and you will see the sentiment score for your comment. Hooray!