📧 Complete Notification Channels Implementation for Production Alerting

# 📧 Complete Notification Channels Implementation for Production Alerting

## Problem Statement

The alerting system has comprehensive structure but **missing critical notification implementations**:

**Current State in `mcp-logging/src/alerting.rs`:**
- Line 623: `// TODO: Implement webhook sending`
- Line 627: `// TODO: Implement email sending`  
- Line 631: `// TODO: Implement Slack notification`
- Line 635: `// TODO: Implement PagerDuty notification`
- Line 432: `// TODO: Support custom metrics`
- Line 552: `// TODO: Implement resolution logic based on metrics`

**Impact:**
- Alerting system is non-functional for production deployments
- No way to receive notifications when issues occur  
- Framework appears incomplete for enterprise usage
- Monitoring capabilities are severely limited

## Motivation

### Production Requirements
- **Enterprise deployments** require multiple notification channels
- **SRE teams** need PagerDuty integration for on-call management
- **Development teams** need Slack/email for immediate awareness
- **Automation systems** need webhook callbacks for self-healing

### Industry Standards
Based on 2025 monitoring best practices:
- **Multi-channel alerting** is required for production systems
- **Alert routing** based on severity levels
- **Escalation policies** for critical incidents
- **Alert de-duplication** to prevent noise

## Solution Design

### 1. Notification Channel Implementations

#### Webhook Notifications
```rust
#[async_trait]
impl NotificationChannel for WebhookChannel {
    async fn send_alert(&self, alert: &Alert) -> Result<(), NotificationError> {
        let payload = serde_json::json!({
            "alert_id": alert.id,
            "severity": alert.severity,
            "message": alert.message,
            "timestamp": alert.timestamp,
            "metadata": alert.metadata
        });
        
        let response = self.client
            .post(&self.webhook_url)
            .header("Content-Type", "application/json")
            .header("User-Agent", "PulseEngine-MCP-Alert/1.0")
            .json(&payload)
            .send()
            .await?;
            
        if !response.status().is_success() {
            return Err(NotificationError::WebhookFailed(response.status()));
        }
        
        Ok(())
    }
}
```

#### Email Notifications
```rust
impl EmailChannel {
    async fn send_alert(&self, alert: &Alert) -> Result<(), NotificationError> {
        let subject = format!("[{}] Alert: {}", 
            alert.severity.to_string().to_uppercase(),
            alert.rule_name
        );
        
        let body = format!(
            "Alert Details:\n\nSeverity: {:?}\nMessage: {}\nTime: {}\nServer: {}\n\nMetadata:\n{:#?}",
            alert.severity,
            alert.message, 
            alert.timestamp,
            alert.server_info.name,
            alert.metadata
        );
        
        self.smtp_client
            .send_email(&self.to_addresses, &subject, &body)
            .await?;
            
        Ok(())
    }
}
```

#### Slack Integration  
```rust
impl SlackChannel {
    async fn send_alert(&self, alert: &Alert) -> Result<(), NotificationError> {
        let color = match alert.severity {
            AlertSeverity::Critical => "#FF0000",  // Red
            AlertSeverity::High => "#FF8C00",      // Orange  
            AlertSeverity::Medium => "#FFD700",    // Yellow
            AlertSeverity::Low => "#32CD32",       // Green
            AlertSeverity::Info => "#87CEEB",      // Blue
        };
        
        let attachment = slack_api::Attachment {
            color: Some(color.to_string()),
            title: Some(format!("MCP Alert: {}", alert.rule_name)),
            text: Some(alert.message.clone()),
            fields: vec![
                slack_api::Field {
                    title: "Severity".to_string(),
                    value: alert.severity.to_string(),
                    short: true,
                },
                slack_api::Field {
                    title: "Server".to_string(),
                    value: alert.server_info.name.clone(),
                    short: true,
                }
            ],
            ts: Some(alert.timestamp.timestamp()),
            ..Default::default()
        };
        
        self.slack_client
            .post_message(&self.channel, &attachment)
            .await?;
            
        Ok(())
    }
}
```

#### PagerDuty Integration
```rust
impl PagerDutyChannel {
    async fn send_alert(&self, alert: &Alert) -> Result<(), NotificationError> {
        let event_action = match alert.state {
            AlertState::Active => "trigger",
            AlertState::Resolved => "resolve",
            AlertState::Acknowledged => "acknowledge",
            AlertState::Suppressed => return Ok(()), // Skip suppressed
        };
        
        let payload = PagerDutyEvent {
            routing_key: self.routing_key.clone(),
            event_action: event_action.to_string(),
            dedup_key: Some(alert.id.to_string()),
            payload: PagerDutyPayload {
                summary: format!("MCP Alert: {}", alert.message),
                severity: match alert.severity {
                    AlertSeverity::Critical | AlertSeverity::High => "critical",
                    AlertSeverity::Medium => "warning", 
                    AlertSeverity::Low | AlertSeverity::Info => "info",
                },
                source: alert.server_info.name.clone(),
                timestamp: alert.timestamp,
                custom_details: alert.metadata.clone(),
            },
        };
        
        self.client
            .post("https://events.pagerduty.com/v2/enqueue")
            .json(&payload)
            .send()
            .await?;
            
        Ok(())
    }
}
```

### 2. Custom Metrics Support
```rust
// Replace TODO at line 432
impl AlertEvaluator {
    fn evaluate_custom_metric(&self, metric_type: &MetricType) -> f64 {
        match metric_type {
            MetricType::Custom(name) => {
                self.custom_metrics
                    .get(name)
                    .and_then(|metric| metric.current_value())
                    .unwrap_or(0.0)
            }
            _ => 0.0,
        }
    }
}

pub trait CustomMetricProvider {
    fn get_metric_value(&self, name: &str) -> Option<f64>;
    fn get_metric_metadata(&self, name: &str) -> Option<HashMap<String, String>>;
}
```

### 3. Alert Resolution Logic
```rust  
// Replace TODO at line 552
impl AlertManager {
    async fn resolve_alert_if_needed(&self, alert_id: &Uuid) -> Result<(), AlertError> {
        let alert = self.get_alert(alert_id).await?;
        let rule = self.get_rule(&alert.rule_id).await?;
        
        // Re-evaluate the rule condition
        let current_metrics = self.metrics_collector.collect().await?;
        let condition_met = self.evaluator.evaluate(&rule.condition, &current_metrics);
        
        if !condition_met {
            // Condition no longer triggered, resolve the alert
            self.update_alert_state(alert_id, AlertState::Resolved).await?;
            
            // Send resolution notification
            for channel in &rule.notification_channels {
                if let Err(e) = channel.send_resolution(&alert).await {
                    tracing::warn!("Failed to send resolution notification: {}", e);
                }
            }
        }
        
        Ok(())
    }
}
```

## Implementation Plan

### Phase 1: Core Notification Channels (Week 1)
- [ ] Implement WebhookChannel with retry logic
- [ ] Implement EmailChannel with SMTP support  
- [ ] Add basic configuration and error handling
- [ ] Create integration tests for each channel

### Phase 2: Advanced Integrations (Week 2)
- [ ] Implement SlackChannel with rich formatting
- [ ] Implement PagerDutyChannel with escalation policies
- [ ] Add channel-specific configuration options
- [ ] Create notification templates and customization

### Phase 3: Custom Metrics & Resolution (Week 3)
- [ ] Implement CustomMetricProvider trait
- [ ] Add custom metrics evaluation logic
- [ ] Implement alert resolution automation
- [ ] Add metrics-based alert lifecycle management

### Phase 4: Production Features (Week 4)
- [ ] Add notification rate limiting
- [ ] Implement alert aggregation and de-duplication
- [ ] Add notification channel failover
- [ ] Create monitoring dashboard for alert system

## Configuration Examples

### Environment-Based Setup
```bash
# Webhook notifications
MCP_ALERT_WEBHOOK_URL=https://my-webhook.example.com/alerts

# Email notifications  
MCP_ALERT_EMAIL_SMTP_HOST=smtp.gmail.com
MCP_ALERT_EMAIL_FROM=alerts@mycompany.com
MCP_ALERT_EMAIL_TO=team@mycompany.com,oncall@mycompany.com

# Slack integration
MCP_ALERT_SLACK_TOKEN=xoxb-your-slack-token
MCP_ALERT_SLACK_CHANNEL=#alerts

# PagerDuty integration
MCP_ALERT_PAGERDUTY_ROUTING_KEY=your-routing-key
```

### Programmatic Configuration
```rust
let alert_config = AlertConfig {
    rules: vec![
        AlertRule {
            id: "high_error_rate".to_string(),
            condition: AlertCondition::threshold("error_rate", ">", 0.05),
            severity: AlertSeverity::Critical,
            notification_channels: vec![
                NotificationChannelConfig::PagerDuty(PagerDutyConfig {
                    routing_key: env::var("PAGERDUTY_KEY")?,
                    severity_mapping: SeverityMapping::default(),
                }),
                NotificationChannelConfig::Slack(SlackConfig {
                    token: env::var("SLACK_TOKEN")?,
                    channel: "#alerts".to_string(),
                })
            ],
        }
    ],
};
```

## Acceptance Criteria

### Functional Requirements
- [ ] All 4 notification channels implemented and tested
- [ ] Custom metrics support with provider trait
- [ ] Alert resolution logic based on metrics  
- [ ] Configuration via environment variables and code
- [ ] Error handling and retry logic for all channels
- [ ] Integration tests covering happy path and failures

### Production Requirements
- [ ] Rate limiting prevents notification spam
- [ ] De-duplication prevents duplicate alerts
- [ ] Failover between notification channels  
- [ ] Monitoring of notification system itself
- [ ] Performance benchmarks show minimal overhead
- [ ] Security audit of notification credentials

### Developer Experience
- [ ] Simple configuration in <10 lines of code
- [ ] Clear error messages for configuration issues
- [ ] Examples for each notification channel
- [ ] Migration guide from placeholder TODOs
- [ ] Documentation covers common use cases

## Dependencies & Integration

### New Dependencies Required
```toml
# Email support
lettre = "0.10"

# Slack API
slack-api = "0.7"  

# HTTP client for webhooks/PagerDuty
reqwest = { version = "0.11", features = ["json"] }

# Templating for notifications
tera = "1.17"
```

### Integration Points
- **Metrics System**: `mcp-monitoring/src/metrics.rs`
- **Configuration**: `mcp-server/src/config.rs`  
- **Middleware**: `mcp-server/src/middleware.rs`
- **Examples**: `examples/` directory for demonstrations

## References & Research

### Production Alerting Standards
- [SRE Alerting Best Practices](https://sre.google/sre-book/monitoring-distributed-systems/)
- [PagerDuty Events API v2](https://developer.pagerduty.com/api-reference/b3A6Mjc0ODEzNw-send-an-event-to-pager-duty)
- [Slack Incoming Webhooks](https://api.slack.com/messaging/webhooks)

### Current Framework Integration  
- Alert system structure: `mcp-logging/src/alerting.rs`
- Metrics collection: `mcp-monitoring/src/collector.rs`
- Configuration patterns: `examples/advanced-server-example/`

### Production Usage Examples
- Loxone MCP Server: Real-world alerting requirements
- Enterprise deployment patterns from community feedback

## Success Metrics

1. **Functional**: All notification channels deliver alerts reliably
2. **Performance**: <100ms notification latency for critical alerts  
3. **Reliability**: 99.9% notification delivery success rate
4. **Usability**: Complete alerting setup in <5 minutes
5. **Production**: Used in 3+ real deployments within 30 days

This completes the alerting system foundation and enables true production-ready deployments with comprehensive monitoring capabilities.

**Priority**: High - Critical missing functionality for production use
**Effort**: Medium - Well-defined implementation scope
**Impact**: High - Enables enterprise monitoring and operations

📧 Complete Notification Channels Implementation for Production Alerting #51

Description

📧 Complete Notification Channels Implementation for Production Alerting

Problem Statement

Motivation

Production Requirements

Industry Standards

Solution Design

1. Notification Channel Implementations

Webhook Notifications

Email Notifications

Slack Integration

PagerDuty Integration

2. Custom Metrics Support

3. Alert Resolution Logic

Implementation Plan

Phase 1: Core Notification Channels (Week 1)

Phase 2: Advanced Integrations (Week 2)

Phase 3: Custom Metrics & Resolution (Week 3)

Phase 4: Production Features (Week 4)

Configuration Examples

Environment-Based Setup

Programmatic Configuration

Acceptance Criteria

Functional Requirements

Production Requirements

Developer Experience

Dependencies & Integration

New Dependencies Required

Integration Points

References & Research

Production Alerting Standards

Current Framework Integration

Production Usage Examples

Success Metrics

Metadata

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