Alfie Mellor

Alfie Mellor


Using a Java Based Kafka Client in a Node.js Application

A step by step guide for developing a Java based Kafka client in a Node.js application using GraalVM.

The first time I heard about GraalVM, it totally blew my mind. Being able to combine multiple languages in a single application or business logic is an incredibly useful and powerful tool.

A real life need for a polyglot application emerged once we decided to switch from RabbitMQ to Kafka as our messaging system. Most of our RMQ consumers were written in Node.js, and moving to a different messaging system would force us either use a Node.js based library, or rewrite our entire business logic.

While there are several Node.js based Kafka clients, using them poses limitations such as the implemented Kafka API version, or the exposed interfaces and customization options. Using a Native Kafka client while maintaining the Node.js business logic would be a real win for us.

This tutorial builds on this awesome medium post on developing with Java and JavaScript together using GraalVM.

We will be using Docker Compose to build and create our images.

A working example can be found here.

Setting up Docker

The minimal needs of our environment are having GraalVM, Zookeeper and Kafka installed. The quickest way to achieve this is by using Docker and Docker Compose to create a complete running environment:

version: '3.3'
    image: 'confluentinc/cp-zookeeper:5.0.0'
    hostname: zookeeper
      - '2181:2181'
      - zk-data:/var/lib/zookeeper/data
      - zk-log:/var/lib/zookeeper/log
    image: 'confluentinc/cp-kafka:5.0.0'
      - '9092:9092'
      - '9093:9093'
      - 'zookeeper'
      KAFKA_ZOOKEEPER_CONNECT: 'zookeeper:2181'
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://localhost:9092,PLAINTEXT2://kafka-broker:9093
      KAFKA_TOPICS: "test_topic"
    image: 'oracle/graalvm-ce:1.0.0-rc12'
      - 'kafka-broker'
      - ./:/code
      VM: 'graalvm'


docker-compose.yml hosted with ❤ by GitHub

A Docker Compose file containing definitions for zookeeper, Kafka and GraalVM.

Running docker-compose up -d from the containing folder will perform the following:

  1. Download a Zookeeper image and run it on port 2181 along with persistent data and log volumes.
  2. Download a Kafka image containing a Kafka broker, and run it. The broker will connect to a Zookeeper on port 2181, and will allow client connections on ports 9092 and 9093.
  3. Download a GraalVM image. This image will have GraalVM and Node.js installed, and will have a shared volume with the host machine in the ./code folder.

All defined ports will be exposed on the local machine (localhost:port). Also, services will recognize each other based on their server name. Accessing Zookeeper from the broker machine will be using zookeeper:2181 as the host name. Same for kafka-broker:9092 for connecting with the Kafka broker.

Setting up the Java client

We are going to be using Java 1.8 and Maven to compile and run our Java client.

Even though the entire Kafka client will reside in a container, it will be helpful to run and debug our code directly from the host machine, using our favorite IDE. To do that, Maven and Java need to be installed on the host machine. Connection to other containers will be done using localhost as the host name.

Setting up Maven

You can use this tutorial to start a new Maven based Java project, or just use the following pom file:

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="" xmlns:xsi=""


  <!-- FIXME change it to the project's website -->


    <!-- -->
    <!-- -->
    <!-- -->


pom.xml hosted with ❤ by GitHub

The above pom file will create the required Java application file structure, along with all the required dependencies.

Notice the ‘maven-shade-plugin’ we are using to compile a single ‘uber-jar’ for the client and all of its dependencies. This will make it easier for us to add the client to the Node.js application later.

Make sure to change to your desired package name.

Creating a Kafka client

Next step is creating our Kafka client (consumer and producer).

We will implement a basic Kafka producer and then a consumer.

Add a file under /src/main/java/my/group/id:


import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.StringSerializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Iterator;
import org.json.*;
import java.util.Properties;
import java.util.concurrent.ExecutionException;

public class Producer {

    public static void main(String[] args) {
        Producer p = new Producer("{\"bootstrap.servers\": \"localhost:9092\", }");
        try {
            p.put("test_topic", "msgKey", "msgData");
        catch (Exception e) {
            System.out.println("Error Putting" + e);

    private Properties produceProperties;
    private final KafkaProducer<String, String> mProducer;
    private final Logger mLogger = LoggerFactory.getLogger(Producer.class);

    public Producer(String config) {
        mProducer = new KafkaProducer<>(produceProperties);"Producer initialized");

    public void put(String topic, String key, String value) throws ExecutionException, InterruptedException {"Put value: " + value + ", for key: " + key);

        ProducerRecord<String, String> record = new ProducerRecord<>(topic, key, value);
        mProducer.send(record, (recordMetadata, e) -> {
        if (e != null) {
            mLogger.error("Error while producing", e);
        }"Received new meta. Topic: " + recordMetadata.topic()
            + "; Partition: " + recordMetadata.partition()
            + "; Offset: " + recordMetadata.offset()
            + "; Timestamp: " + recordMetadata.timestamp());

    void close() {"Closing producer's connection");

    private void extractPropertiesFromJson(String jsonString) {
        produceProperties = new Properties();
        JSONObject jsonObject = new JSONObject(jsonString.trim());
        Iterator<String> keys = jsonObject.keys();
        while(keys.hasNext()) {
            String key =;
            produceProperties.setProperty(key, (String)jsonObject.get(key));
        String deserializer = StringSerializer.class.getName();
        produceProperties.setProperty(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, deserializer);
        produceProperties.setProperty(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, deserializer);
} hosted with ❤ by GitHub

The producer in the example above can receive its configuration in a JSON format, and sends a string type message.

The main function in the Producer is an easy way of running the code and sending a test message.

Add a file in the same folder:


import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.errors.WakeupException;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Properties;
import java.util.Collections;
import java.util.Iterator;
import java.time.Duration;
import java.util.concurrent.CountDownLatch;
import org.json.*;
import java.util.Queue; 

public class Consumer {

    // a concurrent queue shared with Node
    private final Queue<Object> mQueue;     
    private Properties consumProperties;
    private final Logger mLogger = LoggerFactory.getLogger(Consumer.class.getName());
    public Consumer(Queue<Object> queue, String config){
      mQueue = queue;

    public void start() {
        CountDownLatch latch = new CountDownLatch(1);

        ConsumerRunnable consumerRunnable = new ConsumerRunnable(consumProperties, latch, mQueue);
        Thread thread = new Thread(consumerRunnable);
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
  "Caught shutdown hook");

  "Application has exited");

    private void await(CountDownLatch latch) {
        try {
        } catch (InterruptedException e) {
          mLogger.error("Application got interrupted", e);
        } finally {
"Application is closing");
    private void extractPropertiesFromJson(String jsonString) {
        consumProperties = new Properties();
        JSONObject jsonObject = new JSONObject(jsonString.trim());
        Iterator<String> keys = jsonObject.keys();
        while(keys.hasNext()) {
            String key =;
            consumProperties.setProperty(key, (String)jsonObject.get(key));
        String deserializer = StringDeserializer.class.getName();
        consumProperties.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, deserializer);
        consumProperties.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, deserializer);

    private class ConsumerRunnable implements Runnable {

        private KafkaConsumer<String, String> mConsumer;
        private CountDownLatch mLatch;
        private Queue mQueue;

        ConsumerRunnable(Properties config, CountDownLatch latch, Queue queue) {
            mLatch = latch;
            mQueue = queue;
            String topic = (String)config.get("topic");
            mConsumer = new KafkaConsumer<>(config);

        public void run() {
          try {
            while (true) {
              ConsumerRecords<String, String> records = mConsumer.poll(Duration.ofMillis(100));
              for (ConsumerRecord<String, String> record : records) {
      "Key: " + record.key() + ", Value: " + record.value());
      "Partition: " + record.partition() + ", Offset: " + record.offset());
          } catch (WakeupException e) {
  "Received shutdown signal!");
          } finally {

        public void shutdown() {
} hosted with ❤ by GitHub

Same as the producer, this consumer receives its configuration in a JSON format.

After configuring our consumer, we start a new thread that connects to our Kafka broker and polls for messages. Each new message is pushed into a queue which will later be used in our Node.js application.

Compiling the code

Running mvn package form within the root folder, will compile the code into a single jar file named ‘uber-kafka-client-1.0.jar’. This file contains all required java code and dependencies, and will be used as a java library.

Setting up a Node.js Application

Last but not least is our Node.js application.

Add an index.js file under node/services/kafka-user:

const {Worker} = require('worker_threads');

function JavaToJSNotifier() {
    this.queue = new java.util.concurrent.LinkedBlockingDeque();
    this.worker = new Worker(`
        const { workerData, parentPort } = require('worker_threads');
        while (true) {
          // block the worker waiting for the next notification from Java
          var data = workerData.queue.take();
          // notify the main event loop that we got new data 
        { eval: true, workerData: { queue: this.queue }, stdout: true, stderr: true });

const config = {
    "bootstrap.servers": (process.env.VM === 'graalvm') ?'kafka-broker:9093' : 'localhost:9092'

const Consumer = Java.type('');
config.topic = "test_topic";
config[''] = 'Test_Group'

const asyncJavaEvents = new JavaToJSNotifier();
asyncJavaEvents.worker.on('message', (n) => {
    console.log(`Got new data from Java! ${n}`);

const mConsumer = new Consumer(asyncJavaEvents.queue, JSON.stringify(config));

index.js hosted with ❤ by GitHub

The code above creates and configures a new Kafka consumer, and then uses node’s experimental workers to create a new thread that listens to messages from that consumer. The consumer thread notifies the main thread when a new message arrives.

Notice the this.queue = new java.util.concurrent.LinkedBlockingDeque()on line 4. This is possible due to using the GraalVM image. This queue will be a shared instance with the Java consumer we previously defined.

Also, notice the const Consumer = Java.type('')in line 20. Again this is possible due to GraalVM, and will hold a reference to our Java based Kafka consumer.

Running the code

The previously installed GraalVM image already contains node and GraalVM setup. If one wishes to run the node application on the host machine instead, installing and configuring GraalVM is required (instructions).

To run our code inside the container, open a terminal from the root folder and type docker-compose run graalvm sh.

This will open a shell within the GraalVM image.

Due to our configuration all of our compiled code and scripts will be located under the ./code folder.

Run the following command:

node --polyglot --jvm --jvm.cp=code/target/uber-kafka-client-1.0.jar -- experimental-worker code/node/services/kafka-user/index.js

This command will run our node application as a polyglot application in a JVM. Notice the — jvm.cp parameter that tells JVM where to find our Java based Kafka client.

Trying it out

Keep the terminal open, go back to the Java IDE, and run the Producer.main procedure.

You should now see the following printed in you terminal:



GraalVM makes writing polyglot applications easy. Adding a docker infrastructure, makes it even easier to develop and run cross-language applications just about anywhere.

The possibilities are virtually endless.

I hope this helps some of you and maybe inspires you to create some cross-language solutions to a real life problem you are facing.

#java #node-js

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Using a Java Based Kafka Client in a Node.js Application

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Aria Barnes

Aria Barnes


Why use Node.js for Web Development? Benefits and Examples of Apps

Front-end web development has been overwhelmed by JavaScript highlights for quite a long time. Google, Facebook, Wikipedia, and most of all online pages use JS for customer side activities. As of late, it additionally made a shift to cross-platform mobile development as a main technology in React Native, Nativescript, Apache Cordova, and other crossover devices. 

Throughout the most recent couple of years, Node.js moved to backend development as well. Designers need to utilize a similar tech stack for the whole web project without learning another language for server-side development. Node.js is a device that adjusts JS usefulness and syntax to the backend. 

What is Node.js? 

Node.js isn’t a language, or library, or system. It’s a runtime situation: commonly JavaScript needs a program to work, however Node.js makes appropriate settings for JS to run outside of the program. It’s based on a JavaScript V8 motor that can run in Chrome, different programs, or independently. 

The extent of V8 is to change JS program situated code into machine code — so JS turns into a broadly useful language and can be perceived by servers. This is one of the advantages of utilizing Node.js in web application development: it expands the usefulness of JavaScript, permitting designers to coordinate the language with APIs, different languages, and outside libraries.

What Are the Advantages of Node.js Web Application Development? 

Of late, organizations have been effectively changing from their backend tech stacks to Node.js. LinkedIn picked Node.js over Ruby on Rails since it took care of expanding responsibility better and decreased the quantity of servers by multiple times. PayPal and Netflix did something comparative, just they had a goal to change their design to microservices. We should investigate the motivations to pick Node.JS for web application development and when we are planning to hire node js developers. 

Amazing Tech Stack for Web Development 

The principal thing that makes Node.js a go-to environment for web development is its JavaScript legacy. It’s the most well known language right now with a great many free devices and a functioning local area. Node.js, because of its association with JS, immediately rose in ubiquity — presently it has in excess of 368 million downloads and a great many free tools in the bundle module. 

Alongside prevalence, Node.js additionally acquired the fundamental JS benefits: 

  • quick execution and information preparing; 
  • exceptionally reusable code; 
  • the code is not difficult to learn, compose, read, and keep up; 
  • tremendous asset library, a huge number of free aides, and a functioning local area. 

In addition, it’s a piece of a well known MEAN tech stack (the blend of MongoDB, Express.js, Angular, and Node.js — four tools that handle all vital parts of web application development). 

Designers Can Utilize JavaScript for the Whole Undertaking 

This is perhaps the most clear advantage of Node.js web application development. JavaScript is an unquestionable requirement for web development. Regardless of whether you construct a multi-page or single-page application, you need to know JS well. On the off chance that you are now OK with JavaScript, learning Node.js won’t be an issue. Grammar, fundamental usefulness, primary standards — every one of these things are comparable. 

In the event that you have JS designers in your group, it will be simpler for them to learn JS-based Node than a totally new dialect. What’s more, the front-end and back-end codebase will be basically the same, simple to peruse, and keep up — in light of the fact that they are both JS-based. 

A Quick Environment for Microservice Development 

There’s another motivation behind why Node.js got famous so rapidly. The environment suits well the idea of microservice development (spilling stone monument usefulness into handfuls or many more modest administrations). 

Microservices need to speak with one another rapidly — and Node.js is probably the quickest device in information handling. Among the fundamental Node.js benefits for programming development are its non-obstructing algorithms.

Node.js measures a few demands all at once without trusting that the first will be concluded. Many microservices can send messages to one another, and they will be gotten and addressed all the while. 

Versatile Web Application Development 

Node.js was worked in view of adaptability — its name really says it. The environment permits numerous hubs to run all the while and speak with one another. Here’s the reason Node.js adaptability is better than other web backend development arrangements. 

Node.js has a module that is liable for load adjusting for each running CPU center. This is one of numerous Node.js module benefits: you can run various hubs all at once, and the environment will naturally adjust the responsibility. 

Node.js permits even apportioning: you can part your application into various situations. You show various forms of the application to different clients, in light of their age, interests, area, language, and so on. This builds personalization and diminishes responsibility. Hub accomplishes this with kid measures — tasks that rapidly speak with one another and share a similar root. 

What’s more, Node’s non-hindering solicitation handling framework adds to fast, letting applications measure a great many solicitations. 

Control Stream Highlights

Numerous designers consider nonconcurrent to be one of the two impediments and benefits of Node.js web application development. In Node, at whatever point the capacity is executed, the code consequently sends a callback. As the quantity of capacities develops, so does the number of callbacks — and you end up in a circumstance known as the callback damnation. 

In any case, Node.js offers an exit plan. You can utilize systems that will plan capacities and sort through callbacks. Systems will associate comparable capacities consequently — so you can track down an essential component via search or in an envelope. At that point, there’s no compelling reason to look through callbacks.


Final Words

So, these are some of the top benefits of Nodejs in web application development. This is how Nodejs is contributing a lot to the field of web application development. 

I hope now you are totally aware of the whole process of how Nodejs is really important for your web project. If you are looking to hire a node js development company in India then I would suggest that you take a little consultancy too whenever you call. 

Good Luck!

Original Source

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Tyrique  Littel

Tyrique Littel


How to Install OpenJDK 11 on CentOS 8

What is OpenJDK?

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.

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sophia tondon

sophia tondon


Top 10 NodeJs app Development Companies- ValueCoders

Node.js is a prominent tech trend in the space of web and mobile application development. It has been proven very efficient and useful for a variety of application development. Thus, all business owners are eager to leverage this technology for creating their applications.

Are you striving to develop an application using Node.js? But can’t decide which company to hire for NodeJS app development? Well! Don’t stress over it, as the following list of NodeJS app development companies is going to help you find the best partner.

Let’s take a glance at top NodeJS application development companies to hire developers in 2021 for developing a mind-blowing application solution.

Before enlisting companies, I would like to say that every company has a foundation on which they thrive. Their end goals, qualities, and excellence define their competence. Thus, I prepared this list by considering a number of aspects. While making this list, I have considered the following aspects:

  • Review and rating
  • Enlisted by software peer & forums
  • Hourly price
  • Offered services
  • Year of experience (Average 8+ years)
  • Credibility & Excellence
  • Served clients and more

I believe this list will help you out in choosing the best NodeJS service provider company. So, now let’s explore the top NodeJS developer companies to choose from in 2021.

#1. JSGuru

JSGuru is a top-rated NodeJS app development company with an innovative team of dedicated NodeJS developers engaged in catering best-class UI/UX design, software products, and AWS professional services.

It is a team of one of the most talented developers to hire for all types of innovative solution development, including social media, dating, enterprise, and business-oriented solutions. The company has worked for years with a number of startups and launched a variety of products by collaborating with big-name corporations like T-systems.

If you want to hire NodeJS developers to secure an outstanding application, I would definitely suggest them. They serve in the area of eLearning, FinTech, eCommerce, Telecommunications, Mobile Device Management, and more.

  • Ratings: 4.9/5.0

  • Founded: 2006

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  • Price: Starting from $50/hour

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