SyslogClient for Node.js

A TypeScript implementation of a syslog client for Node.js that sends RFC 5424 formatted messages over TCP or UDP to a syslog server.

Features

• Supports TCP and UDP: Choose between TCP or UDP transport protocols.
• RFC 5424 Compliance: Sends properly formatted syslog messages.
• Customizable Identity: Override default options with custom identity settings.
• EventEmitter Integration: Emits connect, disconnect, and error events.
• Reconnection Logic: Automatic reconnection support for TCP connections.
• TypeScript Support: Fully typed for better development experience.

Installation

Install the package using npm:

npm install syslog-client-ts

Usage

Importing the Module

import {
  Facility,
  Identity,
  Severity,
  SyslogClient,
  TCPOptions,
} from 'syslog-client';

Creating an Identity

Define an Identity object with your desired settings:

const identity: Identity = {
  facility: Facility.LOCAL0,
  severity: Severity.INFORMATIONAL,
  appName: 'SpiderVerse',
  syslogHostname: 'spiderverse.dev',
  // pid is optional and defaults to process.pid
};

Instantiating the Client

Create a new SyslogClient instance:

const client = new SyslogClient({
  hostname: 'syslog-server.example.com',
  port: 514,
  transport: 'tcp', // or udp
  identity: identity,
  {
    timeout: 5000,
    reconnect: true,
    reconnectInterval: 2000,
  },
);

Connecting to the Syslog Server

Connect to the server using the connect method:

client
  .connect()
  .then(() => {
    console.log('Connected to syslog server');
  })
  .catch(err => {
    console.error('Connection error:', err);
  });

Sending a Log Message

Use the log method to send messages:

client
  .log('This is a test message')
  .then(() => {
    console.log('Message sent successfully');
  })
  .catch(err => {
    console.error('Error sending message:', err);
  });

Handling Events

Listen to events emitted by the client:

client.on('connect', () => {
  console.log('Client connected');
});

client.on('disconnect', () => {
  console.log('Client disconnected');
});

client.on('error', err => {
  console.error('An error occurred:', err);
});

Disconnecting

When done, disconnect the client:

client.disconnect();

API Reference

SyslogClient Class

Constructor

new SyslogClient({
  options: SyslogClientOptions,
  defaultIdentity: IIdentity,
  options?: ITCPOptions,
});

• hostname: Syslog server hostname or IP address.
• port: Port number of the syslog server.
• transport: Transport protocol ('tcp' or 'udp').
• identity: Identity object containing facility, severity, appName, etc.
• options: Optional TCP options (only applicable for TCP transport).

Methods

• connect(): Promise<void>: Connects to the syslog server.
• log(message: string, options?: LogOptions): Promise<void>: Sends a log message.
• disconnect(): void: Disconnects from the syslog server.

Events

• connect: Emitted upon successful connection.
• disconnect: Emitted when the connection is closed.
• error: Emitted when an error occurs.

Interfaces

Identity

interface IIdentity {
  facility: FacilityType;
  severity: SeverityType;
  appName: string;
  syslogHostname: string;
  pid?: number;
}

TCP Options

interface ITCPOptions {
  timeout?: number; // Socket timeout in milliseconds
  reconnect?: boolean; // Enable automatic reconnection
  reconnectInterval?: number; // Interval between reconnection attempts in milliseconds
}

Enums

Facility

enum Facility {
  KERNEL = 0,
  USER = 1,
  MAIL = 2,
  SYSTEM = 3,
  DAEMON = 3,
  AUTH = 4,
  SYSLOG = 5,
  LPR = 6,
  NEWS = 7,
  UUCP = 8,
  CRON = 9,
  AUTHPRIV = 10,
  FTP = 11,
  AUDIT = 13,
  ALERT = 14,
  LOCAL0 = 16,
  LOCAL1 = 17,
  LOCAL2 = 18,
  LOCAL3 = 19,
  LOCAL4 = 20,
  LOCAL5 = 21,
  LOCAL6 = 22,
  LOCAL7 = 23,
}

Severity

enum Severity {
  EMERGENCY = 0,
  ALERT = 1,
  CRITICAL = 2,
  ERROR = 3,
  WARNING = 4,
  NOTICE = 5,
  INFORMATIONAL = 6,
  DEBUG = 7,
}

Examples

Sending a Simple Message

await client.log('System started successfully');

Overriding Facility and Severity

await client.log('Disk space low', {
  facility: Facility.SYSTEM,
  severity: Severity.WARNING,
});

Using a Custom Identity

const customIdentity: Identity = {
  facility: Facility.LOCAL1,
  severity: Severity.ERROR,
  appName: 'CustomApp',
  syslogHostname: 'custom-host',
  pid: 12345,
};

await client.log('Custom error message', customIdentity);

Handling Reconnection

Enable automatic reconnection for TCP transport:

const client = new SyslogClient({
  hostname: 'syslog-server.example.com',
  port: 514,
  transport: 'tcp',
  identity: identity,
  {
    reconnect: true,
    reconnectInterval: 5000,
  },
);

Error Handling

Listen for errors to handle exceptions:

client.on('error', err => {
  console.error('Error:', err.message);
});

Best Practices

• TCP vs UDP: Use TCP for reliable delivery, UDP for lower overhead.
• Event Listeners: Listen to error events to catch and handle exceptions.
• Resource Management: Call disconnect() when the client is no longer needed.

Development

Building the Project

Compile the TypeScript code using:

yarn build

Running Tests

yarn test

Contributing

Contributions are welcome! Please follow these steps:

1. Fork the repository.
2. Create a new branch (git checkout -b feature/your-feature).
3. Commit your changes (git commit -am 'Add your feature').
4. Push to the branch (git push origin feature/your-feature).
5. Open a pull request.

License

This project is licensed under the MIT License.

Acknowledgments

• Inspired by the need for a flexible syslog client in Node.js applications.
• Follows the RFC 5424 standard for syslog message formatting.

Contact

For questions or support, please open an issue on the GitHub repository.