Query HDFS Data as a SQL Server Database in Node.js

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

CData Connect AI provides a pure MySQL, cloud-to-cloud interface for HDFS, allowing you to easily query live HDFS data in Node.js — without replicating the data to a natively supported database. As you query data in Node.js, CData Connect AI pushes all supported SQL operations (filters, JOINs, etc) directly to HDFS, leveraging server-side processing to quickly return HDFS data.

Configure HDFS Connectivity for NodeJS

Connectivity to HDFS from NodeJS is made possible through CData Connect AI. To work with HDFS data from NodeJS, we start by creating and configuring a HDFS connection.

1. Log into Connect AI, click Sources, and then click Add Connection

2. Select "HDFS" from the Add Connection panel

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 & Test
5. Navigate to the Permissions tab in the Add HDFS Connection page and update the User-based permissions.

Add a Personal Access Token

When connecting to Connect AI through the REST API, the OData API, or the Virtual SQL Server, a Personal Access Token (PAT) is used to authenticate the connection to Connect AI. It is best practice to create a separate PAT for each service to maintain granularity of access.

1. Click on the Gear icon () at the top right of the Connect AI app to open the settings page.
2. On the Settings page, go to the Access Tokens section and click Create PAT.
3. Give the PAT a name and click Create.
4. The personal access token is only visible at creation, so be sure to copy it and store it securely for future use.

With the connection configured and a PAT generated, 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:

• server: tds.cdata.com
• port: 14333
• user: a Connect AI user (e.g. [email protected])
• password: the PAT for the above user
• database: The connection you configured for HDFS (HDFS1)

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

var sql = require('mssql')
var config = {
	server: 'tds.cdata.com',
	port: 14333, 
	user: '[email protected]', //update me
	password: 'CONNECT_USER_PAT', //update me	
	options: {
		encrypt: true,
		database: 'HDFS1'
	}
}

sql.connect(config, err => { 
    if(err){
        throw err ;
    }
    new sql.Request().query('SELECT * FROM Files', (err, result) => {
        console.dir(result)
    })
        
});

sql.on('error', err => {
    console.log("SQL Error: " ,err);
})