NLdoc Base Worker for TypeScript

A foundational worker implementation for TypeScript projects in the NLdoc ecosystem. This library provides a robust base class for creating workers that handle AMQP message processing with built-in file storage capabilities.

Overview

The Base Worker provides a complete foundation for building distributed document processing workers. It handles:

• AMQP Connection Management: Automatic connection setup, health monitoring, and graceful reconnection
• Message Queue Processing: Structured job processing with configurable prefetch limits
• File Storage Integration: Built-in MinIO integration for handling document assets
• Worker Discovery: Automatic worker registration and health reporting
• Error Handling: Comprehensive error types and graceful failure handling
• Logging Integration: Built-in structured logging with the NLdoc logger

Getting Started

Prerequisites

• Node.js >= 22.0.0
• npm >= 10.0.0
• Access to an AMQP broker (RabbitMQ)
• Optional: MinIO instance for file storage

Installation

Install the package via npm:

npm install @nldoc/baseworker

Or using yarn:

yarn add @nldoc/baseworker

Basic Usage

import { logger } from '@nldoc/logger'
import { Worker, WorkerConfig, WorkerMessageHandler } from '@nldoc/baseworker'

try {
    if (!process.env.EXCHANGE) {
        throw new Error('No exchange prefix defined')
    }

    const config: WorkerConfig = {
        name: 'your-awesome-worker-name',
        amqpHost: process.env.AMQP_HOST ?? 'localhost',
        amqpPass: process.env.AMQP_PASS,
        amqpPort: process.env.AMQP_PORT ?? '5672',
        amqpProtocol: process.env.AMQP_PROTOCOL ?? 'amqp',
        amqpUser: process.env.AMQP_USER,
        exchangePrefix: process.env.EXCHANGE,
        workerInstanceName: process.env.HOSTNAME ?? '',
        prefetchLimit: 10,
    }

    const handler: WorkerMessageHandler = async ({ job, storage }) => {
        // Get files from storage
        const fileBuffer = await storage.getFileBuffer({
            bucketName: job.bucketName,
            filePath: job.filePath
        })

        // Process the document
        // Your document processing logic here...

        return {
            success: true,
            result: 'Processing completed successfully',
            confidence: 100,
        }
    }

    const worker = new Worker({
        logger,
        messageHandler: handler,
        config,
    })

    await worker.start()
} catch (error) {
    if (error instanceof Error) {
        logger.error('Worker failed to start', { error: error.message })
    }
    throw error
}

Configuration

Worker Configuration

For all available configuration options, see the WorkerConfig type definition in src/types/WorkerConfig.ts.

Environment Variables

Common environment variables for configuration:

AMQP_HOST=localhost
AMQP_PORT=5672
AMQP_PROTOCOL=amqp
AMQP_USER=guest
AMQP_PASS=guest
EXCHANGE=your-exchange-prefix
HOSTNAME=worker-instance-01

Message Handler

Your message handler receives a context object with:

• job: The parsed job data (type: WorkerJob)
• storage: File storage interface for accessing assets
• logger: Structured logger instance

const handler: WorkerMessageHandler = async ({ job, storage, logger }) => {
    logger.info('Processing job', { jobId: job.id })

    // Access job properties
    const { bucketName, filePath, metadata } = job

    // Get file from storage
    const fileBuffer = await storage.getFileBuffer({ bucketName, filePath })

    // Process and return result
    return {
        success: true,
        result: { processedData: 'example' },
        confidence: 95,
        metadata: { processingTime: Date.now() }
    }
}

Worker Features

Automatic Health Monitoring

Workers automatically report their availability status and handle graceful shutdowns.

File Storage Integration

Built-in MinIO integration provides seamless file access:

// Get file as buffer
const buffer = await storage.getFileBuffer({ bucketName, filePath })

// Store result files
await storage.putFile({ bucketName: 'output', filePath: 'result.json', data: resultBuffer })

Error Handling

The library includes comprehensive error types:

• ConnectionError: AMQP connection issues
• InvalidJob: Malformed job data
• WorkerError: General worker errors
• ExternalFileStorageNotReadyError: Storage unavailable

Development

Local Setup

1. Clone the repository:

   git clone https://gitlab.com/logius/nldoc/lib/typescript/baseworker.git
   cd baseworker

2. Install dependencies:

   npm install

3. Build the project:

   npm run build

Available Scripts

• npm run test - Run the test suite with Vitest
• npm run build - Build TypeScript to JavaScript
• npm run check - Type check without emitting files
• npm run lint - Lint the codebase using ESLint
• npm run format - Format code using Prettier
• npm run format:check - Check code formatting
• npm run fix - Auto-fix linting and formatting issues

Testing

Run the test suite:

npm test

Contributing

We welcome contributions! Please ensure:

1. All tests pass (npm test)
2. Code is properly formatted (npm run format:check)
3. Linting rules are followed (npm run lint)
4. Type checking passes (npm run check)

License

This project is licensed under the European Union Public License 1.2 - see LICENSE for details.

Acknowledgements

• Built on AMQP for reliable message queuing
• Integrates with MinIO for object storage