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How to connect to Kafka Data from Google Apps Script


Use CData Connect Server to access Kafka data in Google Apps Script.

Google Apps Script gives you the ability to create custom functionality within your Google documents, including Google Sheets, Google Docs, and more. With CData Connect Server, you get a SQL Server interface for any of the 200+ sources supported by CData, including Kafka. The SQL Server protocol is natively supported through the JDBC service in Google Apps Script, so by utilizing Connect Server, you gain access to live Kafka data within your Google documents.

This article shows how to create a virtual database for Kafka in Connect Server and provides sample scripting for processing Kafka data in a Google Spreadsheet.

Our script only reads data from a specified table, but you can easily extend the script to incorporate update functionality.

CData Connect Server provides a pure SQL Server interface for Kafka, allowing you to easily build reports from live Kafka data in Apps Script — without replicating the data to a natively supported database. As you build visualizations, Apps Script generates SQL queries to gather data. Using optimized data processing out of the box, CData Connect Server pushes all supported SQL operations (filters, JOINs, etc) directly to Kafka, leveraging server-side processing to quickly return the requested Kafka data.

Create a Virtual SQL Server Database for Kafka Data

CData Connect Server uses a straightforward, point-and-click interface to connect to data sources and generate APIs.

  1. Login to Connect Server and click Connections.
  2. Select "Kafka" from Available Data Sources.
  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.

  4. Click Save Changes
  5. Click Privileges -> Add and add the new user (or an existing user) with the appropriate permissions.

With the virtual database created, you are ready to connect to Kafka data from Apps Script.

Connect to Kafka Data with Apps Script

At this point, you should have configured a virtual database for Kafka in Connect Server. All that is left now is to use Google Apps Script to access Connect Server and work with your Kafka data in Google Sheets.

In this section, you will create a script (with a menu option to call the script) to populate a spreadsheet with Kafka data. We have created a sample script and explained the different parts. You can view the raw script at the end of the article.

1. Create an Empty Script

To create a script for your Google Sheet, click Tools Script editor from the Google Sheets menu:

Open Script Editor

2. Declare Class Variables

Create a handful of class variables to be available for any functions created in the script. 

//replace the variables in this block with real values as needed
var address = 'CONNECT_SERVER_URL:port';
var user = 'CONNECT_USER';
var userPwd = 'CONNECT_PASSWORD';
var db = 'kafkadb';
var serverSslCert = '-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----';
var clientSslCert = '-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----';
var clientSslKey  = '-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----';

var dbUrl = 'jdbc:sqlserver://' + address + '/' + db + '?useSSL=true';

3. Add a Menu Option

This function adds a menu option to your Google Sheet, allowing you to use the UI to call your function.

function onOpen() {
  var spreadsheet = SpreadsheetApp.getActive();
  var menuItems = [
    {name: 'Write data to a sheet', functionName: 'connectToApacheKafkaData'}
  ];
  spreadsheet.addMenu('Kafka Data', menuItems);
}
The newly added Menu option.

4. Write a Helper Function

This function is used to find the first empty row in a spreadsheet.

/*
 * Finds the first empty row in a spreadsheet by scanning an array of columns
 * @return The row number of the first empty row.
 */
function getFirstEmptyRowByColumnArray(spreadSheet, column) {
  var column = spreadSheet.getRange(column + ":" + column);
  var values = column.getValues(); // get all data in one call
  var ct = 0;
  while ( values[ct] && values[ct][0] != "" ) {
    ct++;
  }
  return (ct+1);
}

5. Write a Function to Write Kafka Data to a Spreadsheet

The function below writes the Kafka data, using the Google Apps Script JDBC functionality to connect to Connect Server, SELECT data, and populate a spreadsheet. When the script is run, two input boxes will appear:

The first one asks the user to input the name of a sheet to hold the data (if the spreadsheet does not exist, the function creates it).

Input box for sheet selection.

The second asks the user to input the name of a Kafka table to read. If an invalid table is chosen, an error message appears and the function is exited.

Input box for table selection.

Note, while the function is designed for use as a menu option, you can extend it for use as a spreadsheet formula.

/*
 * Reads data from a specified Kafka 'table' and writes it to the specified sheet.
 *    (If the specified sheet does not exist, it is created.)
 */
function connectToApacheKafkaData() {
  var thisWorkbook = SpreadsheetApp.getActive();

  //select a sheet and create it if it does not exist
  var selectedSheet = Browser.inputBox('Which sheet would you like the data to post to?',Browser.Buttons.OK_CANCEL);
  if (selectedSheet == 'cancel')
    return;

  if (thisWorkbook.getSheetByName(selectedSheet) == null)
    thisWorkbook.insertSheet(selectedSheet);
  var resultSheet = thisWorkbook.getSheetByName(selectedSheet);
  var rowNum = 2;

  //select a Kafka 'table'
  var table = Browser.inputBox('Which table would you like to pull data from?',Browser.Buttons.OK_CANCEL);
  if (table == 'cancel')
    return;

  var conn = Jdbc.getConnection(dbUrl, {
    user: user, 
    password: userPwd, 
    _serverSslCertificate: serverSslCert,
    _clientSslCertificate: clientSslCert,
    _clientSslKey:         clientSslKey
  );

  //confirm that var table is a valid table/view
  var dbMetaData = conn.getMetaData();
  var tableSet = dbMetaData.getTables(null, null, table, null);
  var validTable = false;
  while (tableSet.next()) {
    var tempTable = tableSet.getString(3);
    if (table.toUpperCase() == tempTable.toUpperCase()){
      table = tempTable;
      validTable = true;
      break;
    }
  } 
  tableSet.close();
  if (!validTable) {
    Browser.msgBox("Invalid table name: " + table, Browser.Buttons.OK);
    return;
  }

  var stmt = conn.createStatement();

  var results = stmt.executeQuery('SELECT * FROM ' + table);
  var rsmd = results.getMetaData();
  var numCols = rsmd.getColumnCount();

  //if the sheet is empty, populate the first row with the headers
  var firstEmptyRow = getFirstEmptyRowByColumnArray(resultSheet, "A");
  if (firstEmptyRow == 1) {
    //collect column names
    var headers = new Array(new Array(numCols));
    for (var col = 0; col < numCols; col++){
      headers[0][col] = rsmd.getColumnName(col+1);
    }
    resultSheet.getRange(1, 1, headers.length, headers[0].length).setValues(headers);
  } else {
    rowNum = firstEmptyRow;
  }

  //write rows of Kafka data to the sheet
  var values = new Array(new Array(numCols));
  while (results.next()) {
    for (var col = 0; col < numCols; col++) {
      values[0][col] = results.getString(col + 1);
    }
    resultSheet.getRange(rowNum, 1, 1, numCols).setValues(values);
    rowNum++;
  }

  results.close();
  stmt.close();
}

When the function is completed, you have a spreadsheet populated with your Kafka data, and you can now leverage all of the calculating, graphing, and charting functionality of Google Sheets anywhere you have access to the Internet.

Complete Google Apps Script

//replace the variables in this block with real values as needed
var address = 'CONNECT_SERVER_URL:port';
var user = 'CONNECT_USER';
var userPwd = 'CONNECT_PASSWORD';
var db = 'kafkadb';
var serverSslCert = '-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----';
var clientSslCert = '-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----';
var clientSslKey  = '-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----';

var dbUrl = 'jdbc:sqlserver://' + address + '/' + db + '?useSSL=true';

function onOpen() {
  var spreadsheet = SpreadsheetApp.getActive();
  var menuItems = [
    {name: 'Write table data to a sheet', functionName: 'connectToApacheKafkaData'}
  ];
  spreadsheet.addMenu('Kafka Data', menuItems);
}

/*
 * Finds the first empty row in a spreadsheet by scanning an array of columns
 * @return The row number of the first empty row.
 */
function getFirstEmptyRowByColumnArray(spreadSheet, column) {
  var column = spreadSheet.getRange(column + ":" + column);
  var values = column.getValues(); // get all data in one call
  var ct = 0;
  while ( values[ct] && values[ct][0] != "" ) {
    ct++;
  }
  return (ct+1);
}

/*
 * Reads data from a specified 'table' and writes it to the specified sheet.
 *    (If the specified sheet does not exist, it is created.)
 */
function connectToApacheKafkaData() {
  var thisWorkbook = SpreadsheetApp.getActive();

  //select a sheet and create it if it does not exist
  var selectedSheet = Browser.inputBox('Which sheet would you like the data to post to?',Browser.Buttons.OK_CANCEL);
  if (selectedSheet == 'cancel')
    return;

  if (thisWorkbook.getSheetByName(selectedSheet) == null)
    thisWorkbook.insertSheet(selectedSheet);
  var resultSheet = thisWorkbook.getSheetByName(selectedSheet);
  var rowNum = 2;

  //select a Kafka 'table'
  var table = Browser.inputBox('Which table would you like to pull data from?',Browser.Buttons.OK_CANCEL);
  if (table == 'cancel')
    return;

  var conn = Jdbc.getConnection(dbUrl, {
    user: user, 
    password: userPwd, 
    _serverSslCertificate: serverSslCert,
    _clientSslCertificate: clientSslCert,
    _clientSslKey:         clientSslKey
  );

  //confirm that var table is a valid table/view
  var dbMetaData = conn.getMetaData();
  var tableSet = dbMetaData.getTables(null, null, table, null);
  var validTable = false;
  while (tableSet.next()) {
    var tempTable = tableSet.getString(3);
    if (table.toUpperCase() == tempTable.toUpperCase()){
      table = tempTable;
      validTable = true;
      break;
    }
  } 
  tableSet.close();
  if (!validTable) {
    Browser.msgBox("Invalid table name: " + table, Browser.Buttons.OK);
    return;
  }

  var stmt = conn.createStatement();

  var results = stmt.executeQuery('SELECT * FROM ' + table);
  var rsmd = results.getMetaData();
  var numCols = rsmd.getColumnCount();

  //if the sheet is empty, populate the first row with the headers
  var firstEmptyRow = getFirstEmptyRowByColumnArray(resultSheet, "A");
  if (firstEmptyRow == 1) {
    //collect column names
    var headers = new Array(new Array(numCols));
    for (var col = 0; col < numCols; col++){
      headers[0][col] = rsmd.getColumnName(col+1);
    }
    resultSheet.getRange(1, 1, headers.length, headers[0].length).setValues(headers);
  } else {
    rowNum = firstEmptyRow;
  }

  //write rows of Kafka data to the sheet
  var values = new Array(new Array(numCols));
  while (results.next()) {
    for (var col = 0; col < numCols; col++) {
      values[0][col] = results.getString(col + 1);
    }
    resultSheet.getRange(rowNum, 1, 1, numCols).setValues(values);
    rowNum++;
  }

  results.close();
  stmt.close();
}