Node.js Drivers

• YugabyteDB node-postgres Smart Driver
• PostgreSQL node-postgres Driver

YugabyteDB node-postgres smart driver is a Node.js driver for YSQL built on the PostgreSQL node-postgres driver, with additional connection load balancing features.

For more information on the YugabyteDB node-postgres smart driver, see the following:

• YugabyteDB smart drivers for YSQL
• CRUD operations
• GitHub repository
• Smart Driver architecture

Download the driver dependency

Download and install the YugabyteDB node-postgres smart driver using the following command (you need to have Node.js installed on your system):

npm install @yugabytedb/pg

The driver requires YugabyteDB version 2.7.2.0 or higher.

You can start using the driver in your code.

Fundamentals

Learn how to perform the common tasks required for Node.js application development using the YugabyteDB node-postgres smart driver.

Load balancing connection properties

The following connection properties need to be added to enable load balancing:

• loadBalance - enable cluster-aware load balancing by setting this property to true; disabled by default.
• topologyKeys - provide comma-separated geo-location values to enable topology-aware load balancing. Geo-locations can be provided as cloud.region.zone. Specify all zones in a region as cloud.region.*. To designate fallback locations for when the primary location is unreachable, specify a priority in the form :n, where n is the order of precedence. For example, cloud1.datacenter1.rack1:1,cloud1.datacenter1.rack2:2.

By default, the driver refreshes the list of nodes every 300 seconds (5 minutes). You can change this value by including the ybServersRefreshInterval parameter.

Use the driver

To use the driver, do the following:

• Pass new connection properties for load balancing in the connection URL.

  To enable uniform load balancing across all servers, set the loadBalance property to true in the URL, as per the following connection string:

  const connectionString = "postgresql://user:password@localhost:port/database?loadBalance=true"
  const client = new Client(connectionString);
  client.connect()
  

  After the driver establishes the initial connection, it fetches the list of available servers from the universe and performs load balancing of subsequent connection requests across these servers.

• To specify topology keys, set the topologyKeys property to comma separated values, as per the following connection string:

  const connectionString = "postgresql://user:password@localhost:port/database?loadBalance=true&topologyKeys=cloud1.datacenter1.rack1,cloud1.datacenter1.rack2"
  const client = new Client(connectionString);
  client.conn
  

• To configure a basic connection pool of maximum 100 connections using Pool, specify load balance as follows:

  let pool = new Pool({
      user: 'yugabyte',
      password: 'yugabyte',
      host: 'localhost',
      port: 5433,
      loadBalance: true,
      database: 'yugabyte',
      max: 100
  })
  

Try it out

This tutorial shows how to use the YugabyteDB node-postgres smart driver with YugabyteDB. It starts by creating a three-node cluster with a replication factor of 3. This tutorial uses the yb-ctl utility.

Next, you use a Node.js application to demonstrate the driver's load balancing features.

Create a local cluster

Create a universe with a 3-node RF-3 cluster with some fictitious geo-locations assigned. The placement values used are just tokens and have nothing to do with actual AWS cloud regions and zones.

cd <path-to-yugabytedb-installation>

./bin/yb-ctl create --rf 3 --placement_info "aws.us-west.us-west-2a,aws.us-west.us-west-2a,aws.us-west.us-west-2b"

Check uniform load balancing

To check uniform load balancing, do the following:

1. Create a Node.js file to run the example:

   touch example.js
   

2. Add the following code in example.js file.

   const pg = require('@yugabytedb/pg');
   
   async function createConnection(){
       const yburl = "postgresql://yugabyte:yugabyte@localhost:5433/yugabyte?loadBalance=true"
       let client = new pg.Client(yburl);
       client.on('error', () => {
           // ignore the error and handle exiting
       })
       await client.connect()
       client.connection.on('error', () => {
           // ignore the error and handle exiting
       })
       return client;
   }
   
   async function createNumConnections(numConnections) {
       let clientArray = []
       for (let i=0; i<numConnections; i++) {
           if(i&1){
                clientArray.push(await createConnection())
           }else  {
               setTimeout(async() => {
                   clientArray.push(await createConnection())
               }, 1000)
           }
       }
       return clientArray
   }
   
   (async () => {
       let clientArray = []
       let numConnections = 30
       clientArray = await createNumConnections(numConnections)
   
       setTimeout(async () => {
           console.log('Node connection counts after making connections: \n\n \t\t', pg.Client.connectionMap, '\n')
       }, 2000)
   
   })();
   

3. Run the example:

   node example.js
   

   The application creates 30 connections and displays a key value pair map where the keys are the host and the values are the number of connections on them (This is the client side perspective of the number of connections). Each node should have 10 connections.

Check topology-aware load balancing

For topology-aware load balancing, run the application with the topologyKeys property set to aws.us-west.us-west-2a; only two nodes will be used in this case.

const pg = require('@yugabytedb/pg');

async function createConnection(){
    const yburl = "postgresql://yugabyte:yugabyte@localhost:5433/yugabyte?loadBalance=true&&topologyKey=aws.us-west.us-west-2a"
    let client = new pg.Client(yburl);
    client.on('error', () => {
        // ignore the error and handle exiting
    })
    await client.connect()
    client.connection.on('error', () => {
        // ignore the error and handle exiting
    })
    return client;
}

async function createNumConnections(numConnections) {
    let clientArray = []
    for (let i=0; i<numConnections; i++) {
        if(i&1){
             clientArray.push(await createConnection())
        }else  {
            setTimeout(async() => {
                clientArray.push(await createConnection())
            }, 1000)
        }
    }
    return clientArray
}

(async () => {
    let clientArray = []
    let numConnections = 30
    clientArray = await createNumConnections(numConnections)

    setTimeout(async () => {
        console.log('Node connection counts after making connections: \n\n \t\t', pg.Client.connectionMap, '\n')
    }, 2000)

})();

To verify the behavior, wait for the app to create connections and then navigate to http://<host>:13000/rpcz. The first two nodes should have 15 connections each, and the third node should have zero connections.

Clean up

When you're done experimenting, run the following command to destroy the local cluster:

./bin/yb-ctl destroy