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Hazelcast Node.js Client

NOTE: This project is currently in active development.

Join the chat at https://gitter.im/hazelcast-incubator/hazelcast-nodejs-client

This document explains Node.js client for Hazelcast which uses Hazelcast's Open Client Protocol 1.0. This client works with Hazelcast 3.6 and higher.

Hazelcast is a clustering and highly scalable data distribution platform. With its various distributed data structures, distributed caching capabilities, elastic nature and more importantly with so many happy users, Hazelcast is a feature-rich, enterprise-ready and developer-friendly in-memory data grid solution.


Hazelcast Node.js client supports the following data structures and features:

  • Map (including entry processors and PartitionAware keys) and MultiMap
  • ReplicatedMap
  • Near Cache support for Map
  • Queue, Set, and List
  • Lock
  • Smart Client
  • Hazelcast Native Serialization
  • Distributed Object Listener
  • Lifecycle Service
  • Ringbuffer
  • Reliable Topic
  • Semaphore
  • Replicated Map
  • Atomic Long
  • SSL connection support (requires enterprise server)

Installing the Client

Following command installs Hazelcast Node.js client:

npm install hazelcast-client --save

Using the Client

Following script illustrates a basic example in which a map is created in Hazelcast Node.js client and an entry is added to that map:

var HazelcastClient = require('hazelcast-client').Client;
var person = {
    firstName: "Joe",
    lastName: "Doe",
    age: 42
var map;
HazelcastClient.newHazelcastClient().then(function (hazelcastClient) {
    map = hazelcastClient.getMap("personMap");
    map.put(1, person).then(function (val) {
        // prints previous value for key `1`
    map.get(1).then(function (value) {

Please see Hazelcast Node.js code samples for more examples.

You can also refer to Hazelcast Node.js API Documentation.

Serialization Considerations

Hazelcast needs to serialize objects in order to be able to keep them in the server memory. For primitive types, it uses Hazelcast native serialization. For other complex types (e.g. JS objects), it uses JSON serialization.

For example, when you try to query your data using predicates, this querying is handled on the server side so Hazelcast does not have to bring all data to the client but only the relevant entries. Otherwise, there would be a lot of unneccessary data traffic between the client and the server and the performance would severely drop. Because predicates run on the server side, the server should be able to reason about your objects. That is why you need to implement serialization on the server side.

The same applies to MapStore. The server should be able to deserialize your objects in order to store them in MapStore.

Regarding arrays in a serializable object, you can use methods like writeIntArray if the array is of a primitive type.

If you have nested objects, these nested objects also need to be serializable. Register the serializers for nested objects and the method writeObject will not have any problem with finding a suitable serializer for and writing/reading the nested object.

If you have arrays of custom objects, you can serialize/deserialize them like the following:

writeData(dataOutput) {
    this.arrayOfCustomObjects.forEach(function(element) {

readData(dataInput) {
    var arrayOfCustomObjects = [];
    var lenOfArray = dataInput.readInt();
    for (i=0;i<lenOfArray;i++) {
    this.arrayOfCustomObjects = arrayOfCustomObjects;


Building And Installing from Sources

Follow the below steps to build and install Hazelcast Node.js client from its source:

  • Clone the GitHub repository https://github.com/hazelcast/hazelcast-nodejs-client.git.
  • Install the dependencies using the command npm install.
  • Compile TypeScript using the command npm run compile.
  • Link the package locally using the command npm link.
  • Run static analysis tool using the command npm run lint

Using Locally Installed Package

  • Change directory to the project directory.
  • Use a locally linked module: npm link hazelcast-client.
  • Tryout the example shown in Using the Client section.


Testing Prerequisites

  • Java 6+
  • Maven

      Maven automatically downloads hazelcast-remote-controller and hazelcast from maven repository.

Running the Tests

Following command starts the tests:

npm test

Release Notes

You can see the release notes for each release on the Releases page.

Mail Group

Please join the mail group if you are interested in using or developing Hazelcast.



Hazelcast is available under the Apache 2 License. Please see the Licensing appendix for more information.


Copyright (c) 2008-2016, Hazelcast, Inc. All Rights Reserved.

Visit www.hazelcast.com for more information.

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