Prometheus Integration

// Enable Prometheus exporter on port 9090 (default host: localhost)
server.EnablePrometheus(9090);

// With custom host (use "+" for all interfaces - requires admin rights)
server.EnablePrometheus("0.0.0.0", 9090);  // Listen on all IPv4
server.EnablePrometheus("localhost", 9090);  // Listen on localhost only (default)
server.EnablePrometheus("+", 9090);  // Listen on all interfaces (requires admin)

// Or with builder pattern
server.EnableMonitoring(builder => builder
    .EnablePrometheus(9090)  // Uses default host: localhost
    .WithUpdateInterval(TimeSpan.FromSeconds(5)));

// With custom host in builder
server.EnableMonitoring(builder => builder
    .EnablePrometheus("0.0.0.0", 9090)
    .WithPrometheusHost("0.0.0.0")  // Alternative way
    .WithUpdateInterval(TimeSpan.FromSeconds(5)));

// Metrics available at http://localhost:9090/metrics (or your configured host)

Advanced Configuration

server.EnableMonitoring(builder => builder
    .EnablePrometheus(9090)
    .EnableOpenTelemetry("http://localhost:4317")
    .WithServiceName("smtp-production")
    .WithServiceVersion("1.0.0")
    .EnableDetailedMetrics()
    .EnableCommandMetrics()
    .EnableThroughputMetrics()
    .EnableHistograms()
    .WithUpdateInterval(TimeSpan.FromSeconds(10))
    .WithLabels(
        ("environment", "production"),
        ("region", "us-east-1"),
        ("instance", "smtp-01"))
    .WithCommandDurationBuckets(1, 5, 10, 25, 50, 100, 250, 500, 1000)
    .WithMessageSizeBuckets(1024, 10240, 102400, 1048576, 10485760));

📊 Available Metrics

Prometheus Metrics

Server Statistics

// Get comprehensive statistics
var stats = server.GetStatistics();

// Basic metrics
Console.WriteLine($"Uptime: {stats.Uptime}");
Console.WriteLine($"Total Sessions: {stats.TotalSessions}");
Console.WriteLine($"Active Sessions: {stats.ActiveSessions}");
Console.WriteLine($"Total Messages: {stats.TotalMessagesReceived}");
Console.WriteLine($"Delivery Rate: {stats.DeliveryRate}%");
Console.WriteLine($"Rejection Rate: {stats.RejectionRate}%");

// Connection metrics
Console.WriteLine($"Connections Accepted: {stats.ConnectionMetrics.AcceptedCount}");
Console.WriteLine($"TLS Usage: {stats.ConnectionMetrics.TlsUsageRate}%");
Console.WriteLine($"Peak Concurrent: {stats.ConnectionMetrics.PeakConcurrentConnections}");

// Authentication metrics
Console.WriteLine($"Auth Success Rate: {stats.AuthenticationMetrics.SuccessRate}%");
Console.WriteLine($"Unique Users: {stats.AuthenticationMetrics.UniqueUsers}");

// Command metrics
foreach (var cmd in stats.CommandMetrics)
{
    Console.WriteLine($"{cmd.Key}: {cmd.Value.AverageDurationMs}ms avg, " +
                      $"{cmd.Value.SuccessRate}% success");
}

// Throughput
var throughput = stats.CurrentThroughput;
Console.WriteLine($"Messages/sec: {throughput.MessagesPerSecond}");
Console.WriteLine($"Bytes/sec: {throughput.BytesPerSecond}");
Console.WriteLine($"Commands/sec: {throughput.CommandsPerSecond}");

🔧 Custom Metrics

// Record custom command metrics
server.RecordMetric("CUSTOM_CMD", success: true, durationMs: 42.5);

// Access metrics collector directly
var collector = server.GetMetricsCollector();
collector.RecordCommand("XCUSTOM", true, 15.3);
collector.RecordAuthentication(true, "CUSTOM_AUTH");
collector.RecordRejection("Custom rejection reason");

📈 Grafana Dashboard

Import Dashboard

1. Import the Zetian SMTP Dashboard
2. Configure Prometheus data source
3. Set server variables

Key Panels

• Rejections - Reasons and trends
• Commands - Execution counts and durations
• Authentication - Success rates by mechanism
• Overview - Sessions, messages, errors, uptime
• Connections - Active/peak connections, TLS usage
• Performance - Latency percentiles, throughput graphs

🔭 OpenTelemetry Integration

Simple Setup

using Zetian.Server;
using Zetian.Monitoring.Extensions;

// Create SMTP server
var server = SmtpServerBuilder.CreateBasic();

// Enable monitoring with OpenTelemetry (automatic tracing & metrics)
server.EnableMonitoring(builder => builder
    .EnableOpenTelemetry("http://localhost:4317") // OTLP endpoint
    .WithServiceName("smtp-production")
    .WithServiceVersion("1.0.0"));

await server.StartAsync();

With Both Prometheus and OpenTelemetry

server.EnableMonitoring(builder => builder
    .EnablePrometheus(9090)                       // Prometheus on port 9090
    .EnableOpenTelemetry("http://localhost:4317") // OpenTelemetry OTLP
    .WithServiceName("smtp-server")
    .WithServiceVersion("1.0.0")
    .EnableDetailedMetrics()
    .EnableCommandMetrics()
    .WithLabels(
        ("environment", "production"),
        ("region", "us-east-1")));

Custom Tracing

// Start a custom activity (span) for your operations
using (var activity = server.StartActivity("custom.operation"))
{
    activity?.SetTag("operation.type", "batch_process");
    activity?.SetTag("batch.size", 100);
    
    // Your custom logic here
    ProcessBatch();
    
    activity?.SetTag("result", "success");
}

// Trace message processing with custom attributes
server.MessageReceived += (sender, e) =>
{
    using var activity = server.StartActivity("message.custom_processing");
    activity?.SetTag("message.size", e.Message.Size);
    activity?.SetTag("sender.host", e.Message.From?.Host);
    activity?.SetTag("sender.address", e.Message.From?.Address);
    
    // Custom processing logic
    if (e.Message.Size > 10_000_000)
    {
        activity?.AddEvent(new ActivityEvent("large_message_detected"));
    }
};

⚙️ Configuration Options

public class MonitoringConfiguration
{
    // Prometheus settings
    public bool EnablePrometheus { get; set; }
    public int? PrometheusPort { get; set; }
    
    // OpenTelemetry settings  
    public bool EnableOpenTelemetry { get; set; }
    public string? OpenTelemetryEndpoint { get; set; }
    
    // Update settings
    public TimeSpan UpdateInterval { get; set; } = TimeSpan.FromSeconds(10);
    
    // Feature toggles
    public bool EnableDetailedMetrics { get; set; } = true;
    public bool EnableCommandMetrics { get; set; } = true;
    public bool EnableThroughputMetrics { get; set; } = true;
    public bool EnableHistograms { get; set; } = true;
    
    // Service identification
    public string ServiceName { get; set; } = "Zetian.SMTP";
    public string ServiceVersion { get; set; } = "1.0.0";
    
    // Custom labels for all metrics
    public Dictionary<string, string> CustomLabels { get; }
}

📊 Monitoring Best Practices

1. Monitor trends - Use Grafana for long-term trend analysis
2. Configure alerting - Set up Prometheus alerts for critical metrics
3. Enable only needed metrics - Disable unused features to reduce overhead
4. Optimize histogram buckets - Adjust buckets based on your traffic patterns
5. Use custom labels - Add environment, region, instance for multi-server setups
6. Set appropriate update intervals - Balance between real-time data and performance

🎯 Performance Impact

• Storage: No persistent storage required
• Network: Minimal (metrics endpoint only)
• CPU Overhead: < 1% with default settings
• Memory Usage: ~10-50MB depending on traffic

🔒 Security

• Monitor for high cardinality metrics
• Sanitize custom labels to prevent metric explosion
• Metrics endpoint should be protected in production
• Use authentication/firewall rules for Prometheus endpoint

📚 Integration Examples

With Docker

FROM mcr.microsoft.com/dotnet/runtime:9.0
EXPOSE 25 9090
# SMTP on 25, Metrics on 9090

With Kubernetes

apiVersion: v1
kind: Service
metadata:
  name: smtp-server
  annotations:
    prometheus.io/scrape: "true"
    prometheus.io/port: "9090"
    prometheus.io/path: "/metrics"

With docker-compose

services:
  smtp:
    image: zetian/smtp:latest
    ports:
      - "25:25"
      - "9090:9090"
  
  prometheus:
    image: prom/prometheus
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
    
  grafana:
    image: grafana/grafana
    ports:
      - "3000:3000"

📋 Requirements

• .NET 8.0, 9.0, or 10.0
• OpenTelemetry packages
• Zetian SMTP Server package
• Prometheus.NET for metrics export

📚 Documentation & Support

• Issues: GitHub Issues
• Examples: GitHub Examples
• Discussions: GitHub Discussions
• Documentation: Zetian Documentation

📄 License

MIT License - see LICENSE

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