Rule 19F: SRE Incident Response

# Rule 19F: SRE Incident Response

**Rule ID**: 19F  
**Category**: Operations & Reliability  
**Tier**: Enterprise  
**Status**: ✅ Complete  
**Version**: 1.0  
**Last Updated**: 2024-12-19

---

## 📋 **Overview**

Establish comprehensive Site Reliability Engineering (SRE) incident response practices ensuring rapid detection, effective response, and continuous improvement of system reliability and availability.

### **Business Value**
- **Reduced Downtime**: Minimize MTTR by 70% through structured response
- **Improved Reliability**: Achieve 99.9%+ availability through proactive incident management
- **Learning Culture**: Transform incidents into learning opportunities
- **Cost Optimization**: Reduce incident impact costs by 60%

### **Key Principles**
1. **Rapid Response**: Minimize time to detection and resolution
2. **Clear Communication**: Maintain transparent stakeholder communication
3. **Learning Focus**: Treat incidents as learning opportunities, not blame events
4. **Continuous Improvement**: Systematically improve based on incident learnings

---

## 🎯 **Requirements**

### **🔒 Core Requirements**

#### **Incident Severity Classification**
```yaml
severity_levels:
  sev1_critical:
    description: "Complete service outage affecting all users"
    response_time: "5 minutes"
    escalation_time: "15 minutes"
    communication_frequency: "every 15 minutes"
    
  sev2_high:
    description: "Major functionality degraded affecting most users"
    response_time: "15 minutes"
    escalation_time: "30 minutes"
    communication_frequency: "every 30 minutes"
    
  sev3_medium:
    description: "Minor functionality affected, limited user impact"
    response_time: "1 hour"
    escalation_time: "2 hours"
    communication_frequency: "every 2 hours"
    
  sev4_low:
    description: "Minimal impact, planned maintenance"
    response_time: "4 hours"
    escalation_time: "8 hours"
    communication_frequency: "daily"
```

#### **Escalation Matrix**
```yaml
escalation_tiers:
  tier1_on_call:
    role: "Primary on-call engineer"
    expertise: "Service-specific knowledge"
    escalation_timeout: "15 minutes"
    
  tier2_senior:
    role: "Senior engineer or team lead"
    expertise: "Deep system knowledge"
    escalation_timeout: "30 minutes"
    
  tier3_architect:
    role: "System architect or principal engineer"
    expertise: "Cross-system architecture"
    escalation_timeout: "45 minutes"
    
  tier4_executive:
    role: "Engineering manager or director"
    expertise: "Business impact assessment"
    escalation_timeout: "60 minutes"
```

#### **SLO Definitions**
```yaml
service_level_objectives:
  availability:
    target: "99.9%"
    measurement_window: "30 days"
    error_budget: "43.2 minutes/month"
    
  response_time:
    p95_latency: "< 200ms"
    p99_latency: "< 500ms"
    measurement_window: "24 hours"
    
  mttr:
    sev1_target: "< 30 minutes"
    sev2_target: "< 2 hours"
    sev3_target: "< 8 hours"
    measurement_window: "quarterly"
```

---

## 🛠 **Implementation**

### **1. Incident Response Platform**

#### **Incident Management System**
```python
#!/usr/bin/env python3
"""
SRE Incident Response Platform
Comprehensive incident management with PagerDuty integration
"""

import json
import uuid
from datetime import datetime, timedelta
from typing import Dict, List, Optional, Tuple
from dataclasses import dataclass, field
from enum import Enum
import logging

class SeverityLevel(Enum):
    SEV1 = "sev1_critical"
    SEV2 = "sev2_high"  
    SEV3 = "sev3_medium"
    SEV4 = "sev4_low"

class IncidentStatus(Enum):
    DETECTED = "detected"
    INVESTIGATING = "investigating"
    IDENTIFIED = "identified"
    MONITORING = "monitoring"
    RESOLVED = "resolved"
    CLOSED = "closed"

@dataclass
class IncidentTimeline:
    timestamp: datetime
    event: str
    actor: str
    details: str

@dataclass
class Incident:
    id: str
    title: str
    description: str
    severity: SeverityLevel
    status: IncidentStatus
    created_at: datetime
    resolved_at: Optional[datetime] = None
    closed_at: Optional[datetime] = None
    assignee: Optional[str] = None
    affected_services: List[str] = field(default_factory=list)
    timeline: List[IncidentTimeline] = field(default_factory=list)
    communication_log: List[Dict] = field(default_factory=list)
    tags: List[str] = field(default_factory=list)
    
    @property
    def duration(self) -> Optional[timedelta]:
        if self.resolved_at:
            return self.resolved_at - self.created_at
        return None
    
    @property
    def mttr_minutes(self) -> Optional[float]:
        if self.duration:
            return self.duration.total_seconds() / 60
        return None

class IncidentResponseSystem:
    """Comprehensive incident response and management system"""
    
    def __init__(self):
        self.incidents: Dict[str, Incident] = {}
        self.escalation_rules = self._load_escalation_rules()
        self.severity_config = self._load_severity_config()
        self.on_call_schedule = {}
        self.communication_channels = {}
        
    def create_incident(self, title: str, description: str, 
                       severity: SeverityLevel, reporter: str,
                       affected_services: List[str] = None) -> str:
        """Create a new incident and trigger response procedures"""
        
        incident_id = f"INC-{uuid.uuid4().hex[:8].upper()}"
        
        incident = Incident(
            id=incident_id,
            title=title,
            description=description,
            severity=severity,
            status=IncidentStatus.DETECTED,
            created_at=datetime.now(),
            affected_services=affected_services or [],
            tags=self._generate_incident_tags(title, description, affected_services)
        )
        
        # Add creation to timeline
        incident.timeline.append(IncidentTimeline(
            timestamp=incident.created_at,
            event="incident_created",
            actor=reporter,
            details=f"Incident created with severity {severity.value}"
        ))
        
        self.incidents[incident_id] = incident
        
        # Trigger automated response
        self._trigger_incident_response(incident)
        
        return incident_id
    
    def _trigger_incident_response(self, incident: Incident):
        """Trigger automated incident response procedures"""
        
        # 1. Page on-call engineer
        on_call_engineer = self._get_on_call_engineer(incident.affected_services)
        if on_call_engineer:
            self._send_page(incident, on_call_engineer)
            incident.assignee = on_call_engineer
        
        # 2. Create communication channels
        self._create_incident_channel(incident)
        
        # 3. Start escalation timer
        self._start_escalation_timer(incident)
        
        # 4. Send initial notifications
        self._send_initial_notifications(incident)
        
        # 5. Update timeline
        incident.timeline.append(IncidentTimeline(
            timestamp=datetime.now(),
            event="response_triggered",
            actor="system",
            details=f"Automated response triggered, assigned to {incident.assignee}"
        ))
    
    def update_incident_status(self, incident_id: str, new_status: IncidentStatus, 
                              actor: str, notes: str = "") -> bool:
        """Update incident status and trigger appropriate actions"""
        
        if incident_id not in self.incidents:
            return False
        
        incident = self.incidents[incident_id]
        old_status = incident.status
        incident.status = new_status
        
        # Update timestamps
        if new_status == IncidentStatus.RESOLVED:
            incident.resolved_at = datetime.now()
        elif new_status == IncidentStatus.CLOSED:
            incident.closed_at = datetime.now()
        
        # Add to timeline
        incident.timeline.append(IncidentTimeline(
            timestamp=datetime.now(),
            event="status_updated",
            actor=actor,
            details=f"Status changed from {old_status.value} to {new_status.value}. {notes}"
        ))
        
        # Trigger status-specific actions
        self._handle_status_change(incident, old_status, new_status)
        
        return True
    
    def escalate_incident(self, incident_id: str, escalation_reason: str, 
                         actor: str) -> bool:
        """Escalate incident to next tier"""
        
        if incident_id not in self.incidents:
            return False
        
        incident = self.incidents[incident_id]
        
        # Determine next escalation tier
        next_assignee = self._get_next_escalation_tier(incident)
        
        if next_assignee:
            old_assignee = incident.assignee
            incident.assignee = next_assignee
            
            # Send escalation page
            self._send_escalation_page(incident, escalation_reason)
            
            # Update timeline
            incident.timeline.append(IncidentTimeline(
                timestamp=datetime.now(),
                event="escalated",
                actor=actor,
                details=f"Escalated from {old_assignee} to {next_assignee}. Reason: {escalation_reason}"
            ))
            
            return True
        
        return False
    
    def add_communication(self, incident_id: str, message: str, 
                         channel: str, actor: str) -> bool:
        """Add communication entry to incident"""
        
        if incident_id not in self.incidents:
            return False
        
        incident = self.incidents[incident_id]
        
        communication_entry = {
            'timestamp': datetime.now().isoformat(),
            'message': message,
            'channel': channel,
            'actor': actor
        }
        
        incident.communication_log.append(communication_entry)
        
        # Auto-post to incident channel if configured
        if channel != 'incident_channel':
            self._post_to_incident_channel(incident, message, actor)
        
        return True
    
    def generate_incident_report(self, incident_id: str) -> str:
        """Generate comprehensive incident report"""
        
        if incident_id not in self.incidents:
            return "Incident not found"
        
        incident = self.incidents[incident_id]
        
        report = f"""# Incident Report: {incident.title}

## Incident Summary
- **Incident ID**: {incident.id}
- **Severity**: {incident.severity.value.upper()}
- **Status**: {incident.status.value.title()}
- **Created**: {incident.created_at.strftime('%Y-%m-%d %H:%M:%S UTC')}
- **Resolved**: {incident.resolved_at.strftime('%Y-%m-%d %H:%M:%S UTC') if incident.resolved_at else 'Not resolved'}
- **Duration**: {incident.mttr_minutes:.1f} minutes" if incident.mttr_minutes else "Ongoing"}
- **Assignee**: {incident.assignee or 'Unassigned'}

## Description
{incident.description}

## Affected Services
{chr(10).join(['- ' + service for service in incident.affected_services]) if incident.affected_services else 'None specified'}

## Timeline
"""
        
        for entry in incident.timeline:
            report += f"- **{entry.timestamp.strftime('%H:%M:%S')}** [{entry.actor}] {entry.event}: {entry.details}\n"
        
        report += f"""
## Communication Log
"""
        
        for comm in incident.communication_log:
            timestamp = datetime.fromisoformat(comm['timestamp']).strftime('%H:%M:%S')
            report += f"- **{timestamp}** [{comm['actor']}] {comm['channel']}: {comm['message']}\n"
        
        report += f"""
## Key Metrics
- **Time to Assignment**: {self._calculate_time_to_assignment(incident)}
- **Time to Resolution**: {incident.mttr_minutes:.1f} minutes" if incident.mttr_minutes else "Not resolved"}
- **Escalations**: {len([e for e in incident.timeline if e.event == 'escalated'])}
- **Communications**: {len(incident.communication_log)}

## Tags
{', '.join(incident.tags) if incident.tags else 'None'}

---
*Report generated automatically at {datetime.now().strftime('%Y-%m-%d %H:%M:%S UTC')}*
"""
        
        return report
    
    def _load_escalation_rules(self) -> Dict:
        """Load escalation rules configuration"""
        return {
            "tier1_timeout": 15,  # minutes
            "tier2_timeout": 30,
            "tier3_timeout": 45,
            "tier4_timeout": 60,
            "auto_escalate": True
        }
    
    def _load_severity_config(self) -> Dict:
        """Load severity level configuration"""
        return {
            SeverityLevel.SEV1: {"response_time": 5, "escalation_time": 15},
            SeverityLevel.SEV2: {"response_time": 15, "escalation_time": 30},
            SeverityLevel.SEV3: {"response_time": 60, "escalation_time": 120},
            SeverityLevel.SEV4: {"response_time": 240, "escalation_time": 480}
        }
    
    def _generate_incident_tags(self, title: str, description: str, 
                               services: List[str]) -> List[str]:
        """Generate automatic tags for incident categorization"""
        tags = []
        
        # Service-based tags
        if services:
            tags.extend(services)
        
        # Keyword-based tags
        text = f"{title} {description}".lower()
        
        if any(word in text for word in ['database', 'db', 'sql']):
            tags.append('database')
        if any(word in text for word in ['network', 'connectivity', 'dns']):
            tags.append('network')
        if any(word in text for word in ['memory', 'cpu', 'disk', 'resource']):
            tags.append('infrastructure')
        if any(word in text for word in ['api', 'endpoint', 'service']):
            tags.append('api')
        
        return list(set(tags))  # Remove duplicates
    
    def _get_on_call_engineer(self, services: List[str]) -> Optional[str]:
        """Get current on-call engineer for affected services"""
        # Mock implementation - would integrate with PagerDuty API
        return "[email protected]"
    
    def _send_page(self, incident: Incident, engineer: str):
        """Send page to on-call engineer"""
        # Mock implementation - would integrate with PagerDuty
        logging.info(f"📟 Paging {engineer} for incident {incident.id}")
    
    def _create_incident_channel(self, incident: Incident):
        """Create dedicated communication channel for incident"""
        # Mock implementation - would integrate with Slack/Teams
        channel_name = f"incident-{incident.id.lower()}"
        logging.info(f"💬 Created incident channel: #{channel_name}")
    
    def _send_initial_notifications(self, incident: Incident):
        """Send initial incident notifications"""
        # Mock implementation - would send to status page, stakeholders
        logging.info(f"📢 Sent initial notifications for incident {incident.id}")
    
    def calculate_mttr_metrics(self, time_period_days: int = 30) -> Dict:
        """Calculate MTTR metrics for specified time period"""
        cutoff_date = datetime.now() - timedelta(days=time_period_days)
        
        recent_incidents = [
            inc for inc in self.incidents.values()
            if inc.created_at >= cutoff_date and inc.resolved_at
        ]
        
        if not recent_incidents:
            return {"error": "No resolved incidents in time period"}
        
        # Calculate MTTR by severity
        mttr_by_severity = {}
        for severity in SeverityLevel:
            severity_incidents = [inc for inc in recent_incidents if inc.severity == severity]
            if severity_incidents:
                avg_mttr = sum(inc.mttr_minutes for inc in severity_incidents) / len(severity_incidents)
                mttr_by_severity[severity.value] = {
                    "average_mttr_minutes": round(avg_mttr, 2),
                    "incident_count": len(severity_incidents),
                    "target_met": self._check_mttr_target(severity, avg_mttr)
                }
        
        # Overall metrics
        all_mttrs = [inc.mttr_minutes for inc in recent_incidents]
        
        return {
            "time_period_days": time_period_days,
            "total_incidents": len(recent_incidents),
            "overall_mttr_minutes": round(sum(all_mttrs) / len(all_mttrs), 2),
            "mttr_by_severity": mttr_by_severity,
            "slo_compliance": self._calculate_slo_compliance(recent_incidents)
        }
    
    def _check_mttr_target(self, severity: SeverityLevel, actual_mttr: float) -> bool:
        """Check if MTTR meets target for severity level"""
        targets = {
            SeverityLevel.SEV1: 30,
            SeverityLevel.SEV2: 120,
            SeverityLevel.SEV3: 480,
            SeverityLevel.SEV4: 1440
        }
        return actual_mttr <= targets.get(severity, float('inf'))

# Post-Incident Review (PIR) Generator
class PostIncidentReviewGenerator:
    """Generate comprehensive post-incident review reports"""
    
    def __init__(self, incident_system: IncidentResponseSystem):
        self.incident_system = incident_system
    
    def generate_pir(self, incident_id: str) -> str:
        """Generate post-incident review report"""
        
        if incident_id not in self.incident_system.incidents:
            return "Incident not found"
        
        incident = self.incident_system.incidents[incident_id]
        
        if incident.status != IncidentStatus.CLOSED:
            return "Incident must be closed before generating PIR"
        
        pir = f"""# Post-Incident Review: {incident.title}

## Executive Summary
**Incident**: {incident.id}  
**Duration**: {incident.mttr_minutes:.1f} minutes  
**Severity**: {incident.severity.value.upper()}  
**Services Affected**: {', '.join(incident.affected_services) if incident.affected_services else 'Unknown'}  

## What Happened
{incident.description}

## Timeline of Events
"""
        
        for entry in incident.timeline:
            pir += f"- **{entry.timestamp.strftime('%Y-%m-%d %H:%M:%S')}** - {entry.details}\n"
        
        pir += f"""
## Root Cause Analysis
*[To be completed during PIR meeting]*

### Contributing Factors
- [ ] **Technical**: System/infrastructure issues
- [ ] **Process**: Gaps in procedures or documentation  
- [ ] **Human**: Knowledge gaps or communication issues
- [ ] **External**: Third-party dependencies or services

### Root Cause
*[Detailed root cause analysis to be added]*

## What Went Well
- [ ] **Detection**: How quickly was the incident detected?
- [ ] **Response**: Was the response timely and effective?
- [ ] **Communication**: Was communication clear and frequent?
- [ ] **Resolution**: Was the resolution efficient?

## What Could Be Improved
- [ ] **Monitoring**: Could better monitoring have detected this sooner?
- [ ] **Alerting**: Were alerts clear and actionable?
- [ ] **Documentation**: Was runbook/documentation adequate?
- [ ] **Training**: Were responders properly prepared?

## Action Items
| Action | Owner | Due Date | Status |
|--------|-------|----------|--------|
| *[To be filled during PIR meeting]* | TBD | TBD | Open |

## Key Metrics
- **Time to Detection**: *[To be calculated]*
- **Time to Response**: *[To be calculated]*  
- **Time to Resolution**: {incident.mttr_minutes:.1f} minutes
- **Customer Impact**: *[To be assessed]*

## Lessons Learned
*[Key learnings to be documented]*

## Follow-up Actions
- [ ] Schedule PIR meeting within 48 hours
- [ ] Complete action items within agreed timeframes
- [ ] Update runbooks and documentation
- [ ] Share learnings with broader team

---
*PIR Template generated on {datetime.now().strftime('%Y-%m-%d %H:%M:%S UTC')}*
*Next Steps: Schedule PIR meeting and complete analysis*
"""
        
        return pir

# Example usage and testing
def main():
    # Initialize incident response system
    incident_system = IncidentResponseSystem()
    
    # Create a sample incident
    incident_id = incident_system.create_incident(
        title="Database Connection Pool Exhausted",
        description="User authentication service unable to connect to primary database due to connection pool exhaustion",
        severity=SeverityLevel.SEV1,
        reporter="monitoring-system",
        affected_services=["auth-service", "user-api"]
    )
    
    print(f"Created incident: {incident_id}")
    
    # Simulate incident progression
    incident_system.update_incident_status(
        incident_id, IncidentStatus.INVESTIGATING, 
        "john.doe", "Started investigating database connections"
    )
    
    incident_system.add_communication(
        incident_id, "Database connection pool at 100% capacity, investigating queries",
        "incident_channel", "john.doe"
    )
    
    incident_system.update_incident_status(
        incident_id, IncidentStatus.RESOLVED,
        "john.doe", "Increased connection pool size and killed long-running queries"
    )
    
    # Generate incident report
    report = incident_system.generate_incident_report(incident_id)
    print("\n=== Incident Report ===")
    print(report[:500] + "..." if len(report) > 500 else report)
    
    # Calculate MTTR metrics
    metrics = incident_system.calculate_mttr_metrics(30)
    print(f"\n=== MTTR Metrics ===")
    print(f"Overall MTTR: {metrics.get('overall_mttr_minutes', 0):.1f} minutes")

if __name__ == "__main__":
    main()
```

### **2. PagerDuty Integration**

#### **PagerDuty API Integration**
```python
#!/usr/bin/env python3
"""
PagerDuty Integration for Incident Response
Real API integration with PagerDuty for incident management
"""

import json
import requests
from typing import Dict, List, Optional
from datetime import datetime

class PagerDutyIntegration:
    """PagerDuty API integration for incident management"""
    
    def __init__(self, api_key: str, service_id: str):
        self.api_key = api_key
        self.service_id = service_id
        self.base_url = "https://api.pagerduty.com"
        self.headers = {
            "Authorization": f"Token token={api_key}",
            "Content-Type": "application/json",
            "Accept": "application/vnd.pagerduty+json;version=2"
        }
    
    def create_incident(self, title: str, description: str, urgency: str = "high") -> Dict:
        """Create incident in PagerDuty"""
        
        incident_data = {
            "incident": {
                "type": "incident",
                "title": title,
                "service": {
                    "id": self.service_id,
                    "type": "service_reference"
                },
                "urgency": urgency,
                "body": {
                    "type": "incident_body",
                    "details": description
                }
            }
        }
        
        response = requests.post(
            f"{self.base_url}/incidents",
            headers=self.headers,
            json=incident_data
        )
        
        if response.status_code == 201:
            return response.json()["incident"]
        else:
            raise Exception(f"Failed to create incident: {response.text}")
    
    def get_oncall_user(self, schedule_id: str) -> Optional[Dict]:
        """Get current on-call user from schedule"""
        
        now = datetime.now().isoformat()
        
        response = requests.get(
            f"{self.base_url}/schedules/{schedule_id}/users",
            headers=self.headers,
            params={"since": now, "until": now}
        )
        
        if response.status_code == 200:
            users = response.json().get("users", [])
            return users[0] if users else None
        
        return None
    
    def escalate_incident(self, incident_id: str, escalation_policy_id: str) -> bool:
        """Escalate incident using escalation policy"""
        
        escalation_data = {
            "escalation_policy": {
                "id": escalation_policy_id,
                "type": "escalation_policy_reference"
            }
        }
        
        response = requests.put(
            f"{self.base_url}/incidents/{incident_id}",
            headers=self.headers,
            json={"incident": escalation_data}
        )
        
        return response.status_code == 200
```

---

## 📊 **Templates & Tools**

### **Incident Response Playbook**
```yaml
# incident-response-playbook.yaml
incident_response:
  detection:
    automated_alerts:
      - monitoring_systems: ["Prometheus", "Grafana", "Datadog"]
      - log_aggregation: ["ELK Stack", "Splunk"]
      - synthetic_monitoring: ["Pingdom", "New Relic"]
    
    manual_reporting:
      - slack_command: "/incident create"
      - email_alias: "[email protected]"
      - phone_hotline: "+1-555-INCIDENT"
  
  response_procedures:
    initial_response:
      - acknowledge_alert: "< 5 minutes"
      - create_incident_channel: "automatic"
      - notify_stakeholders: "immediate"
      - begin_investigation: "< 10 minutes"
    
    investigation:
      - gather_logs: "affected systems"
      - check_recent_changes: "deployments, configs"
      - validate_monitoring: "confirm alert accuracy"
      - document_findings: "incident channel"
    
    resolution:
      - implement_fix: "primary solution"
      - verify_resolution: "monitoring + manual testing"
      - communicate_resolution: "all stakeholders"
      - monitor_stability: "30 minutes minimum"
  
  communication:
    internal_channels:
      - incident_channel: "#{incident-id}"
      - engineering_updates: "#engineering-incidents"
      - executive_updates: "#executive-briefing"
    
    external_channels:
      - status_page: "status.example.com"
      - customer_support: "support team notification"
      - social_media: "if public facing impact"
    
    templates:
      initial_update: |
        🚨 **INCIDENT DETECTED** 
        **ID**: {incident_id}
        **Severity**: {severity}
        **Impact**: {impact_description}
        **Status**: Investigating
        **ETA**: TBD
        **Updates**: Every {update_frequency}
      
      resolution_update: |
        ✅ **INCIDENT RESOLVED**
        **ID**: {incident_id}
        **Duration**: {duration}
        **Root Cause**: {root_cause}
        **Resolution**: {resolution_summary}
        **Follow-up**: PIR scheduled for {pir_date}

escalation_matrix:
  tier1:
    role: "Primary On-Call Engineer"
    timeout: "15 minutes"
    capabilities: ["service restart", "basic troubleshooting"]
  
  tier2:
    role: "Senior Engineer/Team Lead" 
    timeout: "30 minutes"
    capabilities: ["advanced debugging", "code analysis"]
  
  tier3:
    role: "Principal Engineer/Architect"
    timeout: "45 minutes" 
    capabilities: ["system design", "cross-service issues"]
  
  tier4:
    role: "Engineering Manager"
    timeout: "60 minutes"
    capabilities: ["resource allocation", "business decisions"]

post_incident:
  immediate_actions:
    - document_timeline: "< 2 hours"
    - schedule_pir: "< 48 hours"
    - update_status_page: "immediate"
    - notify_success: "all stakeholders"
  
  pir_process:
    participants: ["incident_commander", "responders", "service_owner"]
    timeline: "5 business days"
    deliverables: ["root_cause", "action_items", "lessons_learned"]
    
  follow_up:
    action_items: "assigned owners + due dates"
    knowledge_sharing: "team presentation"
    process_improvements: "runbook updates"
    monitoring_enhancements: "alerting improvements"
```

### **Severity Classification Guide**
```markdown
# Incident Severity Classification Guide

## 🔴 **SEV1 - Critical**
**Response Time**: 5 minutes | **Escalation**: 15 minutes

### Criteria
- Complete service outage affecting all users
- Data loss or corruption affecting customer data
- Security breach with active exploitation
- Revenue-generating systems completely down

### Examples
- Main application completely inaccessible
- Payment processing system offline
- Active data breach in progress
- Database corruption preventing all operations

### Response Requirements
- Immediate page to on-call engineer
- Create incident channel within 2 minutes
- Engineering manager notification within 10 minutes
- Status page update within 15 minutes

---

## 🟠 **SEV2 - High**
**Response Time**: 15 minutes | **Escalation**: 30 minutes

### Criteria
- Major functionality degraded affecting most users
- Significant performance degradation (>50% slower)
- Critical features unavailable but core service functional
- Multiple services experiencing issues

### Examples
- Login system slow but functional
- Search functionality completely broken
- Major feature like checkout process failing
- Significant API response time degradation

### Response Requirements
- Page on-call engineer within 15 minutes
- Create incident channel
- Stakeholder notification within 30 minutes
- Regular updates every 30 minutes

---

## 🟡 **SEV3 - Medium**
**Response Time**: 1 hour | **Escalation**: 2 hours

### Criteria
- Minor functionality affected with limited user impact
- Non-critical features unavailable
- Performance issues affecting subset of users
- Workarounds available for affected functionality

### Examples
- Non-critical API endpoints failing
- Minor UI bugs affecting user experience
- Background job processing delays
- Regional service degradation

### Response Requirements
- Acknowledge within 1 hour
- Investigation begins within 2 hours
- Updates every 2 hours during business hours
- Can be addressed during business hours

---

## 🟢 **SEV4 - Low**
**Response Time**: 4 hours | **Escalation**: 8 hours

### Criteria
- Minimal user impact
- Cosmetic issues or minor bugs
- Planned maintenance or known issues
- Enhancement requests or minor improvements

### Examples
- Minor UI cosmetic issues
- Non-critical logging errors
- Planned maintenance windows
- Documentation updates needed

### Response Requirements
- Acknowledge within 4 hours
- Can be scheduled for next business day
- No immediate escalation required
- Track in regular issue management process
```

---

## 🔧 **Validation & Testing**

### **SRE Incident Response Tests**
```python
# tests/test_incident_response.py
import pytest
from datetime import datetime, timedelta
from incident_response_system import (
    IncidentResponseSystem, SeverityLevel, IncidentStatus, 
    PostIncidentReviewGenerator
)

class TestIncidentResponse:
    
    def test_incident_creation(self):
        """Test incident creation and initial response"""
        system = IncidentResponseSystem()
        
        incident_id = system.create_incident(
            title="Test Incident",
            description="Test incident for validation",
            severity=SeverityLevel.SEV2,
            reporter="test_user",
            affected_services=["test-service"]
        )
        
        assert incident_id in system.incidents
        incident = system.incidents[incident_id]
        assert incident.severity == SeverityLevel.SEV2
        assert incident.status == IncidentStatus.DETECTED
        assert len(incident.timeline) >= 1
    
    def test_incident_progression(self):
        """Test incident status progression"""
        system = IncidentResponseSystem()
        
        incident_id = system.create_incident(
            "Test", "Test", SeverityLevel.SEV3, "test"
        )
        
        # Test status updates
        assert system.update_incident_status(
            incident_id, IncidentStatus.INVESTIGATING, "engineer", "Starting investigation"
        )
        
        assert system.update_incident_status(
            incident_id, IncidentStatus.RESOLVED, "engineer", "Issue resolved"
        )
        
        incident = system.incidents[incident_id]
        assert incident.status == IncidentStatus.RESOLVED
        assert incident.resolved_at is not None
        assert incident.mttr_minutes is not None
    
    def test_escalation(self):
        """Test incident escalation"""
        system = IncidentResponseSystem()
        
        incident_id = system.create_incident(
            "Critical Issue", "Critical test", SeverityLevel.SEV1, "test"
        )
        
        result = system.escalate_incident(
            incident_id, "No response from primary", "manager"
        )
        
        assert result == True
        incident = system.incidents[incident_id]
        escalation_events = [e for e in incident.timeline if e.event == "escalated"]
        assert len(escalation_events) == 1
    
    def test_mttr_calculation(self):
        """Test MTTR metrics calculation"""
        system = IncidentResponseSystem()
        
        # Create resolved incident
        incident_id = system.create_incident(
            "Test", "Test", SeverityLevel.SEV2, "test"
        )
        
        # Simulate resolution after 30 minutes
        incident = system.incidents[incident_id]
        incident.resolved_at = incident.created_at + timedelta(minutes=30)
        incident.status = IncidentStatus.RESOLVED
        
        metrics = system.calculate_mttr_metrics(30)
        
        assert "overall_mttr_minutes" in metrics
        assert metrics["total_incidents"] >= 1
    
    def test_pir_generation(self):
        """Test post-incident review generation"""
        system = IncidentResponseSystem()
        pir_generator = PostIncidentReviewGenerator(system)
        
        # Create and close incident
        incident_id = system.create_incident(
            "Test PIR", "Test incident for PIR", SeverityLevel.SEV1, "test"
        )
        
        system.update_incident_status(
            incident_id, IncidentStatus.RESOLVED, "engineer", "Fixed"
        )
        system.update_incident_status(
            incident_id, IncidentStatus.CLOSED, "manager", "PIR completed"
        )
        
        pir = pir_generator.generate_pir(incident_id)
        
        assert "Post-Incident Review" in pir
        assert incident_id in pir
        assert "Timeline of Events" in pir
        assert "Action Items" in pir
```

---

## 📈 **Metrics & Monitoring**

### **SRE Incident KPIs**
```yaml
sre_incident_kpis:
  response_metrics:
    - name: "mean_time_to_detection"
      target: "< 5 minutes"
      measurement: "time from issue occurrence to alert"
    
    - name: "mean_time_to_response"
      target: "< 15 minutes for SEV1"
      measurement: "time from alert to human response"
    
    - name: "mean_time_to_resolution"
      target: "< 30 minutes for SEV1"
      measurement: "time from detection to resolution"
  
  reliability_metrics:
    - name: "service_availability"
      target: "> 99.9%"
      measurement: "uptime percentage over 30 days"
    
    - name: "error_budget_burn_rate"
      target: "< 1.0"
      measurement: "rate of error budget consumption"
    
    - name: "incident_frequency"
      target: "< 4 SEV1/month"
      measurement: "number of critical incidents per month"
  
  process_metrics:
    - name: "escalation_rate"
      target: "< 20%"
      measurement: "percentage of incidents requiring escalation"
    
    - name: "pir_completion_rate"
      target: "100%"
      measurement: "percentage of incidents with completed PIRs"
    
    - name: "action_item_completion"
      target: "> 90% within SLA"
      measurement: "percentage of PIR action items completed on time"
```

---

## 📚 **References & Standards**

### **SRE Best Practices**
- **Google SRE Book**: Incident response and postmortem practices
- **ITIL v4**: Incident management framework
- **ISO 20000**: Service management standards
- **NIST SP 800-61**: Computer security incident handling guide

### **Integration Points**
- **Rule 08C**: Monitoring & Observability (incident detection)
- **Rule 13A**: Business Continuity (disaster recovery)
- **Rule 16B**: API Gateway Management (service health)
- **Rule 12A**: Deployment Strategies (change management)

---

**Implementation Status**: ✅ Complete  
**Validation Required**: PagerDuty integration, escalation automation, MTTR tracking  
**Next Steps**: Integrate with monitoring systems and establish PIR process