# DLQ Operations Guide

**Navigation:** [📖 Index](DLQ_INDEX.md) | [🚀 Quick Start](DLQ_QUICKSTART.md) | [📚 API Reference](DLQ_API_REFERENCE.md) | [🔧 Operations](DLQ_OPERATIONS.md) | [🏗️ System Guide](DLQ_SYSTEM_GUIDE.md)

---

Comprehensive guide for managing Dead Letter Queues across all queue types.

## Overview

The DLQ system provides queue-native tools for monitoring and managing failed tasks across **all queue types**:
- Partner tasks (`partner_tasks`)
- Job processing (`jobs`)
- Future queue types (notifications, analytics, etc.)

**Key Benefits:**
- Direct RabbitMQ operations (no MongoDB coupling)
- Supports multiple queue types
- Preserves original message content and headers
- Works with any task type

---

## Architecture

### Components

1. **Workers** - Process tasks, send failures to DLQ
   - `workers/partner_sync_worker.js`
   - `workers/job_worker.js`
   - Future workers for other queue types

2. **DLQ Routes** - Global API endpoints
   - `routes/dlq.js`
   - Mounted at `/api/dlq/:queueName/*`

3. **DLQ Controller** - Queue operations logic
   - `controllers/dlq.js`
   - Handles all queue types generically

4. **Monitoring Tools**
   - Web dashboard: `public/dlq-monitor.html`

### Message Flow

```mermaid
flowchart LR
    A[Worker] --> B[Main Queue]
    B --> C{Processing}
    C -->|Success ✓| D[Complete]
    C -->|Failure<br/>max retries| E[DLQ]
    E --> F{Action}
    F -->|Retry| B
    F -->|Archive| G[Archive Storage]
    F -->|Purge| H[Delete]
```

---

## Queue-Native Operations

### Retry Operations

**Retry All Messages (Recommended)**
```bash
curl -X POST http://localhost:4100/api/dlq/partner_tasks/retryAll \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"maxMessages": 50}'
```

**Retry by Position Range (0-based index)**
```bash
curl -X POST http://localhost:4100/api/dlq/partner_tasks/retryByPosition \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"startPosition": 0, "endPosition": 10}'
```

**Retry by Header Match (Custom filtering)**
```bash
curl -X POST http://localhost:4100/api/dlq/partner_tasks/retryByHeader \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"headerKey": "x-retry-count", "headerValue": "1"}'
```

**Benefits:**
- No MongoDB coupling
- Preserves original message content
- Supports multiple queue types
- Direct RabbitMQ operations

---

## Monitoring

### Web Dashboard

Access at `http://localhost:4100/dlq-monitor.html`

Features:
- Real-time statistics
- Message list with error details
- One-click retry operations
- Queue selection dropdown
- Auto-refresh every 30 seconds

---

## Manual Recovery Procedures

### Clear Stuck Processing Tasks

If tasks are stuck in "processing" status:

```bash
mongo mongodb://localhost:27017/agmission << EOF
use agmission
db.partner_log_trackers.updateMany(
  { 
    status: 'processing',
    processingStartedAt: { \$lt: new Date(Date.now() - 90*60*1000) }
  },
  { 
    \$set: { 
      status: 'failed',
      errorMessage: 'Manually reset - stuck processing'
    }
  }
)
EOF
```

### Purge DLQ (Dangerous!)

⚠️ **Warning**: This permanently deletes all DLQ messages.

```bash
curl -X DELETE http://localhost:4100/api/dlq/partner_tasks/purge \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"confirm": true}'
```

---

## Multi-Queue Operations

### Partner Queue
```bash
# View messages
curl http://localhost:4100/api/dlq/partner_tasks/messages \
  -H "Authorization: Bearer $TOKEN"

# Retry all
curl -X POST http://localhost:4100/api/dlq/partner_tasks/retryAll \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"maxMessages": 100}'
```

### Job Queue
```bash
# View messages
curl http://localhost:4100/api/dlq/dev_jobs/messages \
  -H "Authorization: Bearer $TOKEN"

# Retry all
curl -X POST http://localhost:4100/api/dlq/dev_jobs/retryAll \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"maxMessages": 100}'
```

### Future Queues

No code changes needed:
```bash
curl -X POST http://localhost:4100/api/dlq/notifications/retryAll \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"maxMessages": 50}'
```

---

## Alert Thresholds

### Recommended Monitoring

```bash
# Check DLQ count
DLQ_COUNT=$(curl -s http://localhost:4100/api/dlq/partner_tasks/stats \
  -H "Authorization: Bearer $TOKEN" | jq '.dlq.messageCount')

# Alert thresholds
if [ "$DLQ_COUNT" -gt 100 ]; then
  echo "CRITICAL: DLQ has $DLQ_COUNT messages"
elif [ "$DLQ_COUNT" -gt 50 ]; then
  echo "WARNING: DLQ has $DLQ_COUNT messages"
fi
```

**Thresholds:**
- Warning: DLQ > 20 messages
- Critical: DLQ > 50 messages
- Emergency: DLQ > 100 messages OR age > 6 hours

---

## Error Categories

Common error patterns and recovery strategies:

### Transient Errors
- Network timeouts
- Connection failures
- Temporary API unavailability

**Action**: Auto-retry (usually succeeds)

### Validation Errors
- Invalid file format
- Missing required fields
- Data type mismatches

**Action**: Fix source data, then retry

### Infrastructure Errors
- Database connection failures
- Disk space issues
- Memory errors

**Action**: Fix infrastructure, then retry all

---

## Integration with Monitoring Systems

### Prometheus Metrics (Future)

```python
# DLQ message count gauge
dlq_messages_total{queue="partner_tasks"} 5
dlq_messages_total{queue="jobs"} 2

# Retry success rate
dlq_retry_success_rate{queue="partner_tasks"} 0.85
```

### Alert Manager Rules

```yaml
groups:
  - name: dlq_alerts
    rules:
      - alert: HighDLQCount
        expr: dlq_messages_total > 50
        for: 30m
        annotations:
          summary: "High DLQ message count"
```

---

## Best Practices

1. **Regular Monitoring**: Check DLQ counts at least daily
2. **Investigate Patterns**: Multiple similar failures indicate systemic issues
3. **Timely Retry**: Don't let messages age too long
4. **Use Position Retry**: For targeted retry of specific ranges
5. **Document Failures**: Track patterns for future prevention
6. **Test Retry**: Use small batches first to verify fixes

---

## Troubleshooting

### Cannot Connect to RabbitMQ

Check connection settings in `environment.env`:
```env
QUEUE_HOST=localhost
QUEUE_PORT=5672
QUEUE_USR=agm
QUEUE_PWD=***
```

### Messages Not Retrying

1. Check worker is running:
   ```bash
   ps aux | grep partner_sync_worker
   ```

2. Check main queue exists:
   ```bash
   curl http://localhost:15672/api/queues/%2F/dev_partner_tasks \
     -u agm:***
   ```

3. Check message format is valid

### High Failure Rate

1. Review recent error messages
2. Check worker logs for patterns
3. Verify external services are available
4. Review worker configuration

---

## Related Documentation

### 📚 DLQ Documentation

- **[📖 DLQ Index](DLQ_INDEX.md)** - Documentation overview
- **[🚀 Quick Start](DLQ_QUICKSTART.md)** - Get started quickly
- **[📚 API Reference](DLQ_API_REFERENCE.md)** - Complete API docs
- **[🏗️ System Guide](DLQ_SYSTEM_GUIDE.md)** - Architecture details

### 🔗 Additional Resources

- [Worker Configuration](../README.md#workers) - Worker setup
- [Global DLQ Refactoring](../GLOBAL_DLQ_REFACTORING_COMPLETE.md) - Architecture changes
- [Web Dashboard](../public/dlq-monitor.html) - Monitoring interface