Distributed Hazelcast Caching with REST API

This project implements a distributed caching system using Hazelcast across multiple servers. The cache is managed by the Hazelcast distributed map, and the servers use REST API endpoints to interact with the cache. The application is designed to be run across 3 servers, each handling cache operations via the REST API.

Project Structure

• ServerAResource.java: The main resource class exposing REST API endpoints.
  • Implements ping to check server status.
  • Implements addToCache to add data to the distributed cache.
  • Implements getFromCache to retrieve data from the distributed cache.
• CacheConfig.java: Contains the Hazelcast configuration setup.
• AsyncCompletionHandler.java: A utility class to handle asynchronous responses.
• ServerResponse.java: A DTO for standardized server responses.

Prerequisites

To run this application, ensure that you have the following:

• Java 21.
• Maven to manage dependencies and build the project.
• 3 servers configured to run the application on different ports.

Running the Application

You can start the application in 3 different server instances. Each server will run on a different port, for example:

• Server 1: http://localhost:8081
• Server 2: http://localhost:8082
• Server 3: http://localhost:8083

Verify Hazelcast Cluster

After starting all the servers, they should join the same Hazelcast cluster.

API Endpoints

1. Ping Server

Endpoint: /api/ping

Method: GET

Description: A simple health check endpoint that returns a "pong" response from the server.

Example Request:

curl -X GET 'http://localhost:8081/api/ping' \
      -H 'Accept: application/json' \
      -H 'Connection: keep-alive' \
      --compressed

Example Response:

{
  "message": "pong from server A !!!"
}

2. Add Data to Cache

Endpoint: /api/cache/{key}/value/{value}

Method: PUT

Description: Adds a key-value pair to the distributed cache.

• {key}: The key to store in the cache.
• {value}: The value to associate with the given key.

Example Request:

curl -X PUT 'http://localhost:8081/api/cache/abc/value/123' \
      -H 'Accept: application/json' \
      -H 'Connection: keep-alive' \
      --compressed

Example Response:

{
  "message": "Value 123 store for key abc"
}

If the key already exists, it will return a message stating that the value is already present.

Example Response for existing key:

{
  "message": "Value 123 already exist for key abc"
}

3. Get Data from Cache

Endpoint: /api/cache/{key}

Method: GET

Description: Retrieves the value associated with the given key from the distributed cache by sending request to different server.

• {key}: The key to retrieve from the cache.

Example Request:

curl -X GET 'http://localhost:8081/api/cache/abc' \
      -H 'Accept: application/json' \
      -H 'Connection: keep-alive' \
      --compressed

Example Response:

{
  "message": "Value 123 store for key abc"
}

If no value exists for the given key, the response will indicate that no value was found.

Example Response when key is not found:

{
  "message": "No value found for key abc"
}