Extend Google Sheets with Kafka Data

Interact with Kafka data from Google Sheets through macros, custom functions, and add-ons. The CData API Server enables connectivity to Kafka data from cloud-based and mobile applications like Google Sheets. The API Server is a lightweight Web application that produces OData services for Kafka.

Google Apps Script can consume these OData services in the JSON format. This article shows how to create a simple add-on that populates a Google Spreadsheet with SampleTable_1 data and, as you make changes, executes updates to Kafka data.

Set Up the API Server

If you have not already done so, download the CData API Server. Once you have installed the API Server, follow the steps below to begin producing secure Kafka OData services:

Connect to Kafka

To work with Kafka data from Google Sheets, we start by creating and configuring a Kafka connection. Follow the steps below to configure the API Server to connect to Kafka data:

1. First, navigate to the Connections page.
2. Click Add Connection and then search for and select the Kafka connection. 👁 Selecting a data source (SQLite is shown)
   
3. Enter the necessary authentication properties to connect to Kafka.

   Set BootstrapServers and the Topic properties to specify the address of your Apache Kafka server, as well as the topic you would like to interact with.

   Authorization Mechanisms

   • SASL Plain: The User and Password properties should be specified. AuthScheme should be set to 'Plain'.
   • SASL SSL: The User and Password properties should be specified. AuthScheme should be set to 'Scram'. UseSSL should be set to true.
   • SSL: The SSLCert and SSLCertPassword properties should be specified. UseSSL should be set to true.
   • Kerberos: The User and Password properties should be specified. AuthScheme should be set to 'Kerberos'.

   You may be required to trust the server certificate. In such cases, specify the TrustStorePath and the TrustStorePassword if necessary.

   👁 Connecting to a datasource (SQLite is shown)
   
4. After configuring the connection, click Save & Test to confirm a successful connection.

Configure API Server Users

Next, create a user to access your Kafka data through the API Server. You can add and configure users on the Users page. Follow the steps below to configure and create a user:

1. On the Users page, click Add User to open the Add User dialog.
2. Next, set the Role, Username, and Privileges properties and then click Add User. 👁 Configure a new user
   
3. An Authtoken is then generated for the user. You can find the Authtoken and other information for each user on the Users page: 👁 API Server user settings
   

Creating API Endpoints for Kafka

Having created a user, you are ready to create API endpoints for the Kafka tables:

1. First, navigate to the API page and then click Add Table . 👁 Add tables
   
2. Select the connection you wish to access and click Next. 👁 Select the connection (SQLite is shown)
   
3. With the connection selected, create endpoints by selecting each table and then clicking Confirm. 👁 Adding tables from the connection (SQLite is shown)
   

Gather the OData Url

Having configured a connection to Kafka data, created a user, and added resources to the API Server, you now have an easily accessible REST API based on the OData protocol for those resources. From the API page in API Server, you can view and copy the API Endpoints for the API:

👁 API Endpoints

Retrieve Kafka Data

Open the Script Editor from your spreadsheet by clicking Tools -> Script Editor. In the Script Editor, add the following function to populate a spreadsheet with the results of an OData query:

function retrieve(){
 var url = "https://MyUrl/api.rsc/SampleTable_1?select=Id,Id,Column1,Column2";
 var response = UrlFetchApp.fetch(url,{
 headers: {"Authorization": "Basic " + Utilities.base64Encode("MyUser:MyAuthtoken")}
 }); 
 var json = response.getContentText();
 var sheet = SpreadsheetApp.getActiveSheet();
 var a1 = sheet.getRange('a1');
 var index=1;
 var sampletable_1 = JSON.parse(json).value;

 var cols = [["Id","Id","Column1","Column2"]]; 
 sheet.getRange(1,1,1,4).setValues(cols);

 row=2;
 for(var i in sampletable_1){
 for (var j in sampletable_1[i]) {
 switch (j) {
 case "Id":
 a1.offset(row,0).setValue(account[i][j]);
 break;
 case "Id":
 a1.offset(row,1).setValue(account[i][j]);
 break;
 case "Column1":
 a1.offset(row,2).setValue(account[i][j]);
 break;
 case "Column2":
 a1.offset(row,3).setValue(account[i][j]);
 break;
 } 
 }
 row++;
 }
}

Follow the steps below to add an installable trigger to populate the spreadsheet when opened:

1. Click Resources -> Current Project's Triggers -> Add a New Trigger.
2. Select retrieve in the Run menu.
3. Select From Spreadsheet.
4. Select On open.

After closing the dialog, you are prompted to allow access to the application.

Post Changes to Kafka Data

Add the following function to post changes to cells back to the API Server:

function buildReq(e){
 var sheet = SpreadsheetApp.getActiveSheet();
 var changes = e.range;
 var id = sheet.getRange(changes.getRow(),1).getValue();
 var col = sheet.getRange(1,changes.getColumn()).getValue();
 
 var url = "http://MyServer/api.rsc/SampleTable_1("+id+")";
 var putdata = "{\"@odata.type\" : \"CDataAPI.SampleTable_1\", \""+col+"\": \""+changes.getValue()+"\"}";;
 UrlFetchApp.fetch(url,{
 method: "put",
 contentType: "application/json",
 payload: putdata,
 headers: {"Authorization": "Basic " + Utilities.base64Encode("MyUser:MyAuthtoken")}
 });

}

Follow the steps below to add the update trigger:

1. Click Resources -> Current Project's Triggers.
2. Select buildReq in the Run menu.
3. Select From Spreadsheet.
4. Select On edit.

You can test the script by clicking Publish -> Test as Add-On. Select the version, installation type, and spreadsheet to create a test configuration. You can then select and run the test configuration.

As you make changes to cells, the API Server executes updates to Kafka data.