jobs-monorepo/MIGRATION_SUMMARY.md

NATS to RabbitMQ Migration Summary

Migration Overview

Successfully migrated the jobs-scraper project from NATS JetStream to RabbitMQ message queue system.

Changes Made

1. Dependencies Updated

• Removed: github.com/nats-io/nats.go v1.46.1
• Added: github.com/rabbitmq/amqp091-go v1.10.0
• Cleaned up: Removed NATS-related indirect dependencies (nats-io/nkeys, nats-io/nuid)

2. Infrastructure Changes

• Directory: Renamed infrastructure/nats/ → infrastructure/rabbitmq/
• File: Renamed nats.go → rabbitmq.go
• Client: NatsClient → RabbitMQClient

3. RabbitMQ Implementation Features

Message Queue Architecture

• Main Exchange: scraper_exchange (topic exchange)
• Dead Letter Exchange: scraper_dlx (direct exchange)
• Queues:
  • scraper.linkedin
  • scraper.indeed
  • scraper.bayt
  • scraper.tokyodev
  • scraper.japandev
• Dead Letter Queues: Each queue has corresponding _dlq for failed messages

Production-Ready Features

• Durable Queues: Messages persist across server restarts
• Message Persistence: DeliveryMode: amqp.Persistent
• Manual Acknowledgment: Messages only removed after successful processing
• Dead Letter Exchange: Failed messages routed to DLX after max retries
• Message TTL: 24-hour expiration to prevent queue buildup
• QoS Control: Prefetch count of 1 for controlled message delivery
• Retry Logic: Up to 3 delivery attempts before DLX routing

4. Code Changes

Files Modified

1. api/main.go

   • Import: infrastructure/nats → infrastructure/rabbitmq
   • Client: nats.NewNatsClient() → rabbitmq.NewRabbitMQClient()
   • Variable: nc → rmq

2. api/app/app.go

   • Import: infrastructure/nats → infrastructure/rabbitmq
   • Parameter: *nats.NatsClient → *rabbitmq.RabbitMQClient
   • Variable: nc → rmq

3. api/commands/job/create-job.go

   • Import: infrastructure/nats → infrastructure/rabbitmq
   • Struct field: nc *nats.NatsClient → rmq *rabbitmq.RabbitMQClient
   • Method call: nats.LinkedInSubTopic → rabbitmq.LinkedInQueue

4. scraper/main.go

   • Import: infrastructure/nats → infrastructure/rabbitmq
   • Removed: github.com/nats-io/nats.go import
   • Client: NewNatsClient() → NewRabbitMQClient()
   • Subscribe method: Changed from NATS message handler to RabbitMQ message handler
   • Handler signature: func(msg *nats.Msg) → func(data []byte) error

5. inspect_nats.go → inspect_rabbitmq.go

   • Complete rewrite for RabbitMQ queue inspection
   • Features: Queue status, message counts, dead letter queue monitoring

6. Makefile

   • Target: nats-server → rabbitmq-server
   • Command: NATS Docker command → RabbitMQ Docker command

5. Handler Interface Changes

NATS Handler (Old)

func(msg *nats.Msg) {
    // Process msg.Data
    msg.Ack() // or msg.Nak()
}

RabbitMQ Handler (New)

func(data []byte) error {
    // Process data
    return nil // or return error for retry
}

6. Configuration Changes

Environment Variables

• Added: RABBITMQ_URL=amqp://guest:guest@localhost:5672/
• Default: Falls back to localhost if not set

Connection Settings

• Retry Logic: 5 connection attempts with 5-second delays
• Auto-reconnect: Built into RabbitMQ client
• Channel Management: Single channel per client instance

Migration Benefits

1. Enhanced Reliability

• Message Persistence: Messages survive server restarts
• Dead Letter Exchange: Failed messages captured for analysis
• Durable Queues: Queue definitions persist across restarts
• Manual Acknowledgment: Prevents message loss

2. Better Monitoring

• Management UI: Web interface at http://localhost:15672
• Queue Metrics: Message counts, consumer counts, processing rates
• Dead Letter Monitoring: Track failed message patterns
• Custom Inspection Tool: inspect_rabbitmq.go for queue status

3. Production Readiness

• Horizontal Scaling: Multiple consumers per queue
• Load Balancing: Round-robin message distribution
• Backpressure Control: QoS prefetch limits
• Message TTL: Prevents infinite queue growth

4. Operational Improvements

• Industry Standard: RabbitMQ is widely adopted
• Rich Ecosystem: Extensive tooling and monitoring
• Documentation: Comprehensive official documentation
• Community Support: Large community and resources

Testing Verification

✅ Build Tests: All components compile successfully

• go build ./api/... - ✅ Success
• go build ./scraper - ✅ Success
• go build ./inspect_rabbitmq.go - ✅ Success

✅ Dependency Management: go mod tidy completed without errors

✅ Import Resolution: All RabbitMQ imports resolve correctly

Usage Instructions

1. Start RabbitMQ

make rabbitmq-server
# OR
docker run --rm -p 5672:5672 -p 15672:15672 rabbitmq:3-management

2. Start API Server

cd api && go run main.go

3. Start Scraper Worker

cd scraper && go run main.go

4. Monitor Queues

go run inspect_rabbitmq.go
# OR visit http://localhost:15672 (guest/guest)

Rollback Plan

If rollback is needed:

1. Revert go.mod changes
2. Restore infrastructure/nats/ directory
3. Revert all import statements
4. Restore NATS-specific handler signatures
5. Run go mod tidy

Next Steps

1. Test with RabbitMQ: Start RabbitMQ server and test message flow
2. Monitor Performance: Compare performance with previous NATS implementation
3. Configure Production: Set up RabbitMQ cluster for production deployment
4. Update Documentation: Ensure all documentation reflects RabbitMQ usage
5. Team Training: Brief team on RabbitMQ management and monitoring

Migration Status: ✅ COMPLETE

The migration from NATS to RabbitMQ has been successfully completed. All code compiles, dependencies are resolved, and the system is ready for testing with RabbitMQ.