Query HDFS Data as a SQL Server in Node.js

You can use CData Connect Server to query HDFS data through a SQL Server interface. Follow the procedure below to create a virtual database for HDFS in Connect Server and start querying using Node.js.

CData Connect Server provides a pure SQL Server interface for HDFS, allowing you to easily build reports from live HDFS data in Node.js — without replicating the data to a natively supported database. As you build visualizations, Node.js 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 HDFS, leveraging server-side processing to quickly return the requested HDFS data.

Create a Virtual SQL Server Database for HDFS 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 "HDFS" from Available Data Sources.
3. Enter the necessary authentication properties to connect to HDFS.

   In order to authenticate, set the following connection properties:

   • Host: Set this value to the host of your HDFS installation.
   • Port: Set this value to the port of your HDFS installation. Default port: 50070
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 HDFS data from Node.js.

Query HDFS from Node.js

The following example shows how to define a connection and execute queries to HDFS with the SQL Server module. You will need the following information:

• Host name, or address, and port: The address of your Connect Server instance and the port (1433)
• Username and password: The username and password of a user you authorized on Connect Server
• Database name: The database you configured for HDFS (HDFS1)

Connect to HDFS data and start executing queries with the code below:

const sql = require('mssql');

const config = {
    user: 'your_connect_username', 
    password: 'your_connect_password', 
    server: 'connect_server_url', 
    port: 1433, // optional, defaults to 1433
    database: 'HDFS1',
    authentication: {
        type: 'default'
    },
    options: {
        encrypt: true
    }
}

console.log("Starting...");
connectAndQuery();

async function connectAndQuery() {
    try {
        var poolConnection = await sql.connect(config);

        console.log("Reading rows from the table...");
        var resultSet = await poolConnection.request().query(`SELECT * FROM table_name`);

        console.log(`${resultSet.recordset.length} rows returned.`);

        // output column headers
        var columns = "";
        for (var column in resultSet.recordset.columns) {
            columns += column + ", ";
        }
        console.log("%s	", columns.substring(0, columns.length - 2));

        // ouput row contents from default record set
        resultSet.recordset.forEach(row => {
            console.log("%s	%s", row.CategoryName, row.ProductName);
        });

        // close connection only when we're certain application is finished
        poolConnection.close();
    } catch (err) {
        console.error(err.message);
    }
}

SQL Server Access to HDFS Data from Node.js

You have retrieved live HDFS Data using Node.js. Now, you can easily access data sources and more — all without replicating HDFS data.

To get SQL data access to 200+ SaaS, Big Data, and NoSQL sources directly from your applications, try CData Connect Server.