QuestDB Node.js Client

Requirements

The client requires Node.js v16 or newer version.

Installation

npm i -s @questdb/nodejs-client

Examples

Basic API usage

const { Sender } = require('@questdb/nodejs-client');

async function run() {
    const sender = new Sender();

    // connect to QuestDB
    // host and port are required in connect options
    await sender.connect({port: 9009, host: 'localhost'});

    // add rows to the buffer of the sender
    sender.table('prices').symbol('instrument', 'EURUSD')
        .floatColumn('bid', 1.0195).floatColumn('ask', 1.0221)
        .at(Date.now(), 'ms');
    sender.table('prices').symbol('instrument', 'GBPUSD')
        .floatColumn('bid', 1.2076).floatColumn('ask', 1.2082)
        .at(Date.now(), 'ms');

    // flush the buffer of the sender, sending the data to QuestDB
    // the buffer is cleared after the data is sent and the sender is ready to accept new data
    await sender.flush();

    // add rows to the buffer again and send it to the server
    sender.table('prices').symbol('instrument', 'EURUSD')
        .floatColumn('bid', 1.0197).floatColumn('ask', 1.0224)
        .at(Date.now(), 'ms');
    await sender.flush();

    // close the connection after all rows ingested
    await sender.close();
    return new Promise(resolve => resolve(0));
}

run()
    .then(console.log)
    .catch(console.error);

Authentication and secure connection

const { Sender } = require('@questdb/nodejs-client');

async function run() {
    // authentication details
    const CLIENT_ID = 'testapp';
    const PRIVATE_KEY = '9b9x5WhJywDEuo1KGQWSPNxtX-6X6R2BRCKhYMMY6n8';
    const AUTH = {
        keyId: CLIENT_ID,
        token: PRIVATE_KEY
    };

    // pass the authentication details to the sender
    const sender = new Sender({auth: AUTH});

    // connect() takes an optional second argument
    // if 'true' passed the connection is secured with TLS encryption
    await sender.connect({port: 9009, host: 'localhost'}, true);

    // send the data over the authenticated and secure connection
    sender.table('prices').symbol('instrument', 'EURUSD')
        .floatColumn('bid', 1.0197).floatColumn('ask', 1.0224)
        .at(Date.now(), 'ms');
    await sender.flush();

    // close the connection after all rows ingested
    await sender.close();
}

run().catch(console.error);

TypeScript example

import { Sender } from '@questdb/nodejs-client';

async function run(): Promise<number> {
    // authentication details
    const CLIENT_ID: string = 'testapp';
    const PRIVATE_KEY: string = '9b9x5WhJywDEuo1KGQWSPNxtX-6X6R2BRCKhYMMY6n8';
    const AUTH: { kid: string, d: string } = {
        keyId: CLIENT_ID,
        token: PRIVATE_KEY
    };

    // pass the authentication details to the sender
    const sender: Sender = new Sender({auth: AUTH});

    // connect() takes an optional second argument
    // if 'true' passed the connection is secured with TLS encryption
    await sender.connect({port: 9009, host: 'localhost'}, true);

    // send the data over the authenticated and secure connection
    sender.table('prices').symbol('instrument', 'EURUSD')
        .floatColumn('bid', 1.0197).floatColumn('ask', 1.0224).at(Date.now(), 'ms');
    await sender.flush();

    // close the connection after all rows ingested
    await sender.close();
}

run().catch(console.error);

Worker threads example

const { Sender } = require('@questdb/nodejs-client');
const { Worker, isMainThread, parentPort, workerData } = require('worker_threads');

// fake venue
// generates random prices for a ticker for max 5 seconds, then the feed closes
function* venue(ticker) {
    let end = false;
    setTimeout(() => { end = true; }, rndInt(5000));
    while (!end) {
        yield {'ticker': ticker, 'price': Math.random()};
    }
}

// market data feed simulator
// uses the fake venue to deliver price updates to the feed handler (onTick() callback)
async function subscribe(ticker, onTick) {
    const feed = venue(workerData.ticker);
    let tick;
    while (tick = feed.next().value) {
        await onTick(tick);
        await sleep(rndInt(30));
    }
}

async function run() {
    if (isMainThread) {
        const tickers = ['t1', 't2', 't3', 't4'];
        // main thread to start a worker thread for each ticker
        for (let ticker in tickers) {
            const worker = new Worker(__filename, { workerData: { ticker: ticker } })
                .on('error', (err) => { throw err; })
                .on('exit', () => { console.log(`${ticker} thread exiting...`); })
                .on('message', (msg) => {
                    console.log(`Ingested ${msg.count} prices for ticker ${msg.ticker}`);
                });
        }
    } else {
        // it is important that each worker has a dedicated sender object
        // threads cannot share the sender because they would write into the same buffer
        const sender = new Sender();
        await sender.connect({ port: 9009, host: 'localhost' });

        // subscribe for the market data of the ticker assigned to the worker
        // ingest each price update into the database using the sender
        let count = 0;
        await subscribe(workerData.ticker, async (tick) => {
            sender
                .table('prices')
                .symbol('ticker', tick.ticker)
                .floatColumn('price', tick.price)
                .at(Date.now(), 'ms');
            await sender.flush();
            count++;
        });

        // let the main thread know how many prices were ingested
        parentPort.postMessage({'ticker': workerData.ticker, 'count': count});

        // close the connection to the database
        await sender.close();
    }
}

function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

function rndInt(limit) {
    return Math.floor((Math.random() * limit) + 1);
}

run()
    .then(console.log)
    .catch(console.error);