Raft Node Presence Manager

A Node.js implementation for managing node presence in a distributed system using the Raft consensus algorithm and MQTT protocol.

Features

• Manages node presence and active nodes in a distributed network using the MQTT protocol.
• Implements the Raft consensus protocol for leader election and state management.
• Provides easy-to-use methods to handle MQTT connections, subscriptions, and messaging.

Installation

Install the package via npm:

npm install node-raft-over-mqtt

Libraries Used

This project makes use of the following libraries:

• node-mqtt-client: MQTT client for managing secure MQTT connections with certificate-based authentication.

Usage

Here's an example of how to use the NodePresenceManager and RaftNode classes:

Initialization

To set up the Raft node, create an instance and set the required properties.

const { MQTTClient, RaftNode } = require('node-raft-over-mqtt');

// Configure the MQTT client
const mqttClient = new MQTTClient();
mqttClient.host = 'broker.fabris.io';
mqttClient.port = 8883;
mqttClient.protocol = MQTTClient.Protocol.MQTTS;
mqttClient.certificateManager.loadCertificates(
  'authority.pem',
  'certificate.pem',
  'key.pem'
);
mqttClient.connect();

// Unique identifier for the node
const uuid = 'node-1';

// Initialize the Raft node
const raftNode = RaftNode.initialize(mqttClient, uuid);

// Set the logging function
raftNode.logFunction = console.log;

// Start the node
raftNode.start();

MQTT Client Configuration

For detailed configuration options and parameters for the MQTTClient, please refer to the official node-mqtt-client documentation.

Configuration Parameters for RaftNode

| Parameter | Type | Description | Default | |-----------------------|------------|---------------------------------------------------------------------|----------------| | electionTimeout | number | The timeout duration in milliseconds for the election process. | 8000 | | heartbeatInterval | number | The interval in milliseconds between heartbeats sent by the leader. | 2000 | | metric | number | The value used as the node's metric for leader elections. Lower values are considered better. |

RaftNode Public Variables

presenceManager (Read-only)

Returns the instance of the NodePresenceManager associated with the node.

• Returns:
  NodePresenceManager - The presence manager instance.

logFunction

Gets or sets the log function.

• Get: Returns the current log function.
  • Returns: Function - The log function.
• Set: Sets a new log function for logging messages.
  • Parameters: func (Function): The new log function.

metric

Gets or sets the metric value used in leader elections.

• Get: Returns the current metric value.

  • Returns: number - The metric value.

• Set: Sets a new metric value.

  • Parameters: value (number): The new metric value.

leaderMetric (Read-only)

Gets the leader's metric value.

• Returns:
  number - The current leader metric.

RaftNode Public Methods

initialize(mqttClient, uuid)

Initializes a new RaftNode instance if it does not exist.

• mqttClient (MQTTClient): The MQTT client instance.

• uuid (string): The unique identifier for the node.

  • Returns:
    RaftNode - The instance of the RaftNode.

log(message)

Logs a message using the provided log function.

• message (string): The message to log.

start()

Starts the Raft node and initializes its state.

isLeader()

Checks if the current node is the leader.

• Returns:
  boolean - true if the node is a leader, otherwise false.

Versioning

We use SemVer for versioning. For the versions available, see the tags on this repository.

Authors

• Paolo Fabris - Initial work - ubyte.it

See also the list of contributors who participated in this project.

License

This project is licensed under the MIT License. See the LICENSE file for details.