How to make singleton connection in cassandra database in node js

Question

I am using cassandra db so currently every request is creating new connection instance to db. I want if a connection is already establish than skip to create new one. and using a node dependency for connection (cassandra-driver)

Node js 18x

cassendra 3.11.9

cassandra-driver 4.6.4

Current code for create Cassandra connection

 const cassClient = new cassandra.Client({
        contactPoints: ['yourip'],
        pooling: {
          coreConnectionsPerHost: {
            HostDistance:{LOCAL : 2,REMOTE : 1}
          },
          maxRequestsPerConnection: 32768
        },
        localDataCenter: 'ap-south-1',
        keyspace: 'test',
        credentials: { username: 'admin', password: 'admin' }
      });

don't want to create new connection if already a connection is established. want as a singleton pattern connection

Answer 1

A "Singleton" is a simple pattern where you store an instance of an object and your getter create it only if necessary.

You could implement it like this:

var cassandraDatabaseManager = (function () {
    var cassClient;

    function createInstance() {
        return new cassandra.Client({
        contactPoints: ['yourip'],
        pooling: {
          coreConnectionsPerHost: {
            HostDistance:{LOCAL : 2,REMOTE : 1}
          },
          maxRequestsPerConnection: 32768
        },
        localDataCenter: 'ap-south-1',
        keyspace: 'test',
        credentials: { username: 'admin', password: 'admin' }
      });
    }

    return {
        getInstance: function () {
            if (!cassClient) {
                cassClient= createInstance();
            }
            return cassClient;
        }
    };
})();

And you can just use it like this:

const instance = cassandraDatabaseManager.getInstance();