# Disaster Recovery Procedures and Business Continuity

## Overview

This document establishes comprehensive disaster recovery (DR) procedures and business continuity plans to ensure rapid recovery from system failures, natural disasters, and other catastrophic events.

## Disaster Recovery Strategy

### Recovery Objectives

**Recovery Time Objective (RTO):**
- Critical Systems: 1 hour
- Important Systems: 4 hours  
- Standard Systems: 24 hours

**Recovery Point Objective (RPO):**
- Critical Data: 15 minutes
- Important Data: 1 hour
- Standard Data: 24 hours

### DR Site Architecture

**Multi-Region Setup:**
```yaml
# Primary Region: us-east-1
primary_region:
  region: us-east-1
  availability_zones: [us-east-1a, us-east-1b, us-east-1c]
  services:
    - application_servers
    - databases
    - load_balancers
    - storage_systems

# DR Region: us-west-2  
dr_region:
  region: us-west-2
  availability_zones: [us-west-2a, us-west-2b, us-west-2c]
  services:
    - standby_application_servers
    - database_replicas
    - load_balancers
    - replicated_storage
```

## Backup Strategies

### Database Backup Procedures

**Automated Backup Configuration:**
```sql
-- PostgreSQL backup configuration
-- Continuous archiving setup
archive_mode = on
archive_command = 'aws s3 cp %p s3://db-backups/wal/%f'
wal_level = replica

-- Point-in-time recovery setup
SELECT pg_start_backup('daily_backup');
-- File system backup occurs here
SELECT pg_stop_backup();
```

**Backup Automation Script:**
```bash
#!/bin/bash
# scripts/automated-backup.sh

set -e

BACKUP_DATE=$(date +%Y%m%d_%H%M%S)
S3_BUCKET="company-backups"
RETENTION_DAYS=30

# Database backup
echo "Starting database backup..."
pg_dump -h $DB_HOST -U $DB_USER -d $DB_NAME | \
  gzip > "db_backup_${BACKUP_DATE}.sql.gz"

# Upload to S3
aws s3 cp "db_backup_${BACKUP_DATE}.sql.gz" \
  "s3://${S3_BUCKET}/database/db_backup_${BACKUP_DATE}.sql.gz"

# Application data backup
echo "Backing up application data..."
tar -czf "app_data_${BACKUP_DATE}.tar.gz" /var/app/data/
aws s3 cp "app_data_${BACKUP_DATE}.tar.gz" \
  "s3://${S3_BUCKET}/application/app_data_${BACKUP_DATE}.tar.gz"

# Configuration backup
echo "Backing up configurations..."
kubectl get configmaps -o yaml > "configs_${BACKUP_DATE}.yaml"
kubectl get secrets -o yaml > "secrets_${BACKUP_DATE}.yaml"
aws s3 cp "configs_${BACKUP_DATE}.yaml" \
  "s3://${S3_BUCKET}/configs/configs_${BACKUP_DATE}.yaml"

# Cleanup old backups
aws s3 ls "s3://${S3_BUCKET}/database/" | \
  awk '$1 < "'$(date -d "$RETENTION_DAYS days ago" +%Y-%m-%d)'" {print $4}' | \
  xargs -I {} aws s3 rm "s3://${S3_BUCKET}/database/{}"

echo "Backup completed successfully"
```

### Cross-Region Replication

**S3 Cross-Region Replication:**
```json
{
  "Role": "arn:aws:iam::123456789012:role/replication-role",
  "Rules": [
    {
      "ID": "ReplicateToWest",
      "Status": "Enabled",
      "Priority": 1,
      "Filter": {
        "Prefix": "critical-data/"
      },
      "Destination": {
        "Bucket": "arn:aws:s3:::backup-bucket-west",
        "StorageClass": "STANDARD_IA"
      }
    }
  ]
}
```

**Database Replication Setup:**
```bash
# PostgreSQL streaming replication
# On primary server
echo "host replication replica_user 10.0.2.0/24 md5" >> pg_hba.conf

# On replica server
pg_basebackup -h primary_host -D /var/lib/postgresql/data -U replica_user -v -P -W

# recovery.conf on replica
standby_mode = 'on'
primary_conninfo = 'host=primary_host port=5432 user=replica_user'
trigger_file = '/tmp/postgresql.trigger'
```

## Failover Procedures

### Automated Failover

**DNS-Based Failover:**
```yaml
# Route 53 health check configuration
health_check:
  type: HTTPS
  resource_path: /health
  fqdn: api.example.com
  port: 443
  request_interval: 30
  failure_threshold: 3

# Failover routing policy
routing_policy:
  type: FAILOVER
  primary:
    record: api.example.com
    value: 1.2.3.4
    health_check_id: primary_health_check
  
  secondary:
    record: api.example.com  
    value: 5.6.7.8
    health_check_id: secondary_health_check
```

**Application-Level Failover:**
```python
# Circuit breaker pattern for failover
import time
from enum import Enum

class CircuitState(Enum):
    CLOSED = 1
    OPEN = 2
    HALF_OPEN = 3

class CircuitBreaker:
    def __init__(self, failure_threshold=5, timeout=60):
        self.failure_threshold = failure_threshold
        self.timeout = timeout
        self.failure_count = 0
        self.last_failure_time = None
        self.state = CircuitState.CLOSED
    
    def call(self, func, *args, **kwargs):
        if self.state == CircuitState.OPEN:
            if time.time() - self.last_failure_time > self.timeout:
                self.state = CircuitState.HALF_OPEN
            else:
                raise Exception("Circuit breaker is OPEN")
        
        try:
            result = func(*args, **kwargs)
            self.reset()
            return result
        except Exception as e:
            self.record_failure()
            raise e
    
    def record_failure(self):
        self.failure_count += 1
        self.last_failure_time = time.time()
        
        if self.failure_count >= self.failure_threshold:
            self.state = CircuitState.OPEN
    
    def reset(self):
        self.failure_count = 0
        self.state = CircuitState.CLOSED
```

### Manual Failover Procedures

**Emergency Failover Runbook:**
```bash
#!/bin/bash
# scripts/emergency-failover.sh

FAILOVER_REASON=${1:-"Manual failover initiated"}
DR_REGION="us-west-2"

echo "Initiating emergency failover to $DR_REGION"
echo "Reason: $FAILOVER_REASON"

# 1. Notify stakeholders
./scripts/send-emergency-notification.sh "FAILOVER_INITIATED" "$FAILOVER_REASON"

# 2. Stop traffic to primary region
echo "Stopping traffic to primary region..."
aws route53 change-resource-record-sets \
  --hosted-zone-id $HOSTED_ZONE_ID \
  --change-batch file://failover-dns-change.json

# 3. Promote DR database to primary
echo "Promoting DR database..."
aws rds promote-read-replica \
  --db-instance-identifier myapp-db-replica-west

# 4. Update application configuration
echo "Updating application configuration..."
kubectl patch configmap app-config -p '{"data":{"DB_HOST":"myapp-db-west.region.rds.amazonaws.com"}}'

# 5. Scale up DR region resources
echo "Scaling up DR region resources..."
kubectl scale deployment myapp-deployment --replicas=10

# 6. Verify failover success
if ./scripts/verify-dr-health.sh; then
    echo "✓ Failover completed successfully"
    ./scripts/send-emergency-notification.sh "FAILOVER_SUCCESS" "Failover to $DR_REGION completed"
else
    echo "✗ Failover verification failed"
    ./scripts/send-emergency-notification.sh "FAILOVER_FAILED" "Failover verification failed - manual intervention required"
    exit 1
fi

echo "Emergency failover procedure completed"
```

## Recovery Procedures

### System Recovery Steps

**Infrastructure Recovery:**
```bash
#!/bin/bash
# scripts/infrastructure-recovery.sh

RECOVERY_TYPE=${1:-"full"}  # full, partial, data-only

echo "Starting $RECOVERY_TYPE recovery procedure..."

case $RECOVERY_TYPE in
    "full")
        # 1. Restore infrastructure from IaC
        cd terraform/environments/prod
        terraform init
        terraform plan -out=recovery.tfplan
        terraform apply recovery.tfplan
        
        # 2. Restore Kubernetes cluster
        kubectl apply -f k8s/namespace.yaml
        kubectl apply -f k8s/configmaps/
        kubectl apply -f k8s/secrets/
        kubectl apply -f k8s/deployments/
        kubectl apply -f k8s/services/
        ;;
        
    "partial")
        # Restore specific components
        kubectl apply -f k8s/deployments/app-deployment.yaml
        kubectl rollout status deployment/myapp-deployment
        ;;
        
    "data-only")
        # Restore data only
        ./scripts/restore-database.sh
        ./scripts/restore-application-data.sh
        ;;
esac

echo "$RECOVERY_TYPE recovery completed"
```

**Database Recovery:**
```bash
#!/bin/bash
# scripts/restore-database.sh

BACKUP_FILE=${1:-"latest"}
RECOVERY_TARGET=${2:-"latest"}

echo "Starting database recovery..."

# 1. Stop application connections
kubectl scale deployment myapp-deployment --replicas=0

# 2. Restore from backup
if [ "$BACKUP_FILE" = "latest" ]; then
    BACKUP_FILE=$(aws s3 ls s3://company-backups/database/ | sort | tail -n 1 | awk '{print $4}')
fi

echo "Restoring from backup: $BACKUP_FILE"
aws s3 cp "s3://company-backups/database/$BACKUP_FILE" ./
gunzip "$BACKUP_FILE"

# 3. Perform restore
psql -h $DB_HOST -U $DB_USER -d $DB_NAME < "${BACKUP_FILE%.gz}"

# 4. Apply WAL files for point-in-time recovery
if [ "$RECOVERY_TARGET" != "latest" ]; then
    echo "Applying WAL files up to $RECOVERY_TARGET"
    # Point-in-time recovery logic here
fi

# 5. Verify database integrity
./scripts/verify-database-integrity.sh

# 6. Restart applications
kubectl scale deployment myapp-deployment --replicas=3

echo "Database recovery completed"
```

## Testing and Validation

### DR Testing Schedule

**Regular DR Tests:**
- **Monthly**: Backup restoration tests
- **Quarterly**: Partial failover tests  
- **Annually**: Full DR simulation

**DR Test Procedures:**
```bash
#!/bin/bash
# scripts/dr-test.sh

TEST_TYPE=${1:-"backup-restore"}
TEST_DATE=$(date +%Y%m%d_%H%M%S)

echo "Starting DR test: $TEST_TYPE at $TEST_DATE"

case $TEST_TYPE in
    "backup-restore")
        # Test backup restoration in isolated environment
        ./scripts/create-test-environment.sh
        ./scripts/restore-database.sh "test-backup"
        ./scripts/validate-data-integrity.sh
        ./scripts/cleanup-test-environment.sh
        ;;
        
    "failover-simulation")
        # Simulate failover to DR region
        echo "Simulating primary region failure..."
        ./scripts/simulate-region-failure.sh
        ./scripts/emergency-failover.sh "DR Test"
        ./scripts/validate-dr-functionality.sh
        ./scripts/failback-to-primary.sh
        ;;
        
    "full-dr-exercise")
        # Complete DR exercise with all teams
        ./scripts/coordinate-dr-exercise.sh
        ;;
esac

# Generate test report
./scripts/generate-dr-test-report.sh "$TEST_TYPE" "$TEST_DATE"

echo "DR test completed: $TEST_TYPE"
```

### Recovery Validation

**Validation Checklist:**
```bash
#!/bin/bash
# scripts/validate-recovery.sh

echo "Validating recovery procedures..."

# 1. Application health checks
validate_application_health() {
    local endpoints=("https://api.example.com/health" "https://app.example.com/health")
    
    for endpoint in "${endpoints[@]}"; do
        if curl -f -s "$endpoint" > /dev/null; then
            echo "✓ Application healthy: $endpoint"
        else
            echo "✗ Application unhealthy: $endpoint"
            return 1
        fi
    done
}

# 2. Database connectivity and integrity
validate_database() {
    echo "Validating database..."
    
    # Connection test
    if pg_isready -h "$DB_HOST" -p "$DB_PORT" -U "$DB_USER"; then
        echo "✓ Database connectivity verified"
    else
        echo "✗ Database connectivity failed"
        return 1
    fi
    
    # Data integrity test
    local row_count=$(psql -h "$DB_HOST" -U "$DB_USER" -d "$DB_NAME" -t -c "SELECT COUNT(*) FROM users;")
    if [ "$row_count" -gt 0 ]; then
        echo "✓ Database data integrity verified ($row_count users)"
    else
        echo "✗ Database data integrity check failed"
        return 1
    fi
}

# 3. Performance validation
validate_performance() {
    echo "Validating performance..."
    
    # Load test
    local response_time=$(curl -o /dev/null -s -w '%{time_total}' https://api.example.com/health)
    
    if (( $(echo "$response_time < 1.0" | bc -l) )); then
        echo "✓ Performance within acceptable limits: ${response_time}s"
    else
        echo "✗ Performance degraded: ${response_time}s"
        return 1
    fi
}

# Execute validation steps
validate_application_health
validate_database  
validate_performance

echo "✅ Recovery validation completed successfully"
```

## Communication and Coordination

### Emergency Communication Plan

**Communication Tree:**
```yaml
emergency_contacts:
  incident_commander:
    primary: "John Doe <john@example.com> +1-555-0101"
    backup: "Jane Smith <jane@example.com> +1-555-0102"
  
  technical_leads:
    infrastructure: "Bob Wilson <bob@example.com> +1-555-0103"
    application: "Alice Johnson <alice@example.com> +1-555-0104"
    database: "Charlie Brown <charlie@example.com> +1-555-0105"
  
  business_stakeholders:
    ceo: "CEO <ceo@example.com> +1-555-0106"
    cto: "CTO <cto@example.com> +1-555-0107"
    
communication_channels:
  primary: "#incident-response"
  backup: "#emergency-backup"
  executive: "#executive-updates"
```

**Status Page Updates:**
```bash
#!/bin/bash
# scripts/update-status-page.sh

STATUS=${1:-"investigating"}  # investigating, identified, monitoring, resolved
MESSAGE=${2:-"We are investigating reports of service issues"}

curl -X POST "https://api.statuspage.io/v1/pages/$PAGE_ID/incidents" \
  -H "Authorization: OAuth $STATUSPAGE_TOKEN" \
  -d "incident[name]=Service Disruption" \
  -d "incident[status]=$STATUS" \
  -d "incident[message]=$MESSAGE" \
  -d "incident[component_ids][]=$COMPONENT_ID"
```

## Business Continuity Planning

### Critical Business Functions

**Business Impact Analysis:**
```yaml
business_functions:
  customer_orders:
    criticality: high
    rto: 1h
    rpo: 15m
    dependencies: [payment_system, inventory_system]
  
  user_authentication:
    criticality: high  
    rto: 30m
    rpo: 5m
    dependencies: [user_database, session_store]
  
  reporting_system:
    criticality: medium
    rto: 4h
    rpo: 1h
    dependencies: [analytics_database]
```

### Vendor and Supplier Coordination

**Third-Party Dependencies:**
```yaml
critical_vendors:
  aws:
    contact: "AWS Support <support@aws.amazon.com>"
    escalation: "TAM <tam@aws.amazon.com>"
    sla: "99.99% uptime"
  
  payment_processor:
    contact: "Stripe Support <support@stripe.com>"
    escalation: "Account Manager <am@stripe.com>"
    sla: "99.95% uptime"
    
  cdn_provider:
    contact: "CloudFlare Support <support@cloudflare.com>"
    escalation: "Enterprise Support <enterprise@cloudflare.com>"
    sla: "100% uptime"
```

## Compliance and Documentation

### Regulatory Requirements

**Compliance Considerations:**
- SOC 2 Type II audit requirements
- GDPR data protection regulations
- PCI DSS for payment processing
- HIPAA for healthcare data (if applicable)

### Documentation Requirements

**Required DR Documentation:**
- Recovery procedures and runbooks
- Contact lists and escalation procedures
- Business impact analysis
- Risk assessment and mitigation strategies
- Test results and lessons learned

**Documentation Maintenance:**
```bash
#!/bin/bash
# scripts/update-dr-documentation.sh

# Generate current infrastructure inventory
terraform output -json > infrastructure-inventory.json
kubectl get all --all-namespaces -o yaml > kubernetes-inventory.yaml

# Update contact information
./scripts/validate-contact-list.sh
./scripts/update-emergency-contacts.sh

# Review and update procedures
echo "DR documentation updated on $(date)" >> dr-documentation-log.txt

echo "DR documentation update completed"
```
