Production Deployment and Monitoring

Deploying high-performance Go applications to production requires sophisticated deployment strategies, comprehensive monitoring systems, and robust incident response procedures to maintain optimal performance under real-world conditions.

Deployment Strategies

Zero-Downtime Deployment Patterns

Implementing deployment strategies that maintain service availability while enabling continuous performance optimization:

// Advanced deployment orchestrator
type DeploymentOrchestrator struct {
    strategy       DeploymentStrategy
    healthChecker  *HealthChecker
    loadBalancer   *LoadBalancer
    rollback       *RollbackManager
    metrics        *DeploymentMetrics
    notifications  *NotificationService
}

type DeploymentStrategy int

const (
    BlueGreenDeployment DeploymentStrategy = iota
    CanaryDeployment
    RollingDeployment
    A_B_Testing
)

type DeploymentConfig struct {
    Strategy            DeploymentStrategy `yaml:"strategy"`
    HealthCheckEndpoint string            `yaml:"health_check_endpoint"`
    HealthCheckTimeout  time.Duration     `yaml:"health_check_timeout"`
    WarmupDuration      time.Duration     `yaml:"warmup_duration"`
    CanaryTrafficPercent int              `yaml:"canary_traffic_percent"`
    RolloutDuration     time.Duration     `yaml:"rollout_duration"`
    AutoRollbackEnabled bool              `yaml:"auto_rollback_enabled"`
    PerformanceThresholds PerformanceThresholds `yaml:"performance_thresholds"`
}

type PerformanceThresholds struct {
    MaxLatencyP95       time.Duration `yaml:"max_latency_p95"`
    MinThroughput       float64       `yaml:"min_throughput"`
    MaxErrorRate        float64       `yaml:"max_error_rate"`
    MaxMemoryUsage      int64         `yaml:"max_memory_usage"`
    MaxCPUUsage         float64       `yaml:"max_cpu_usage"`
}

// Blue-Green deployment implementation
func (do *DeploymentOrchestrator) ExecuteBlueGreenDeployment(version string, config DeploymentConfig) error {
    deployment := &BlueGreenDeployment{
        Version:       version,
        Config:        config,
        Orchestrator:  do,
        StartTime:     time.Now(),
    }

    // Phase 1: Deploy to Green environment
    fmt.Printf("Phase 1: Deploying version %s to Green environment\n", version)

    greenEnv, err := do.deployToGreenEnvironment(version, config)
    if err != nil {
        return fmt.Errorf("green deployment failed: %v", err)
    }

    // Phase 2: Health check and warmup
    fmt.Printf("Phase 2: Health checking Green environment\n")

    if err := do.healthCheckEnvironment(greenEnv, config); err != nil {
        do.cleanupGreenEnvironment(greenEnv)
        return fmt.Errorf("green environment health check failed: %v", err)
    }

    // Phase 3: Performance validation
    fmt.Printf("Phase 3: Performance validation\n")

    perfResults, err := do.validatePerformance(greenEnv, config.PerformanceThresholds)
    if err != nil {
        do.cleanupGreenEnvironment(greenEnv)
        return fmt.Errorf("performance validation failed: %v", err)
    }

    // Phase 4: Traffic switch
    fmt.Printf("Phase 4: Switching traffic to Green environment\n")

    switchHandle, err := do.loadBalancer.SwitchTrafficToGreen(greenEnv)
    if err != nil {
        do.cleanupGreenEnvironment(greenEnv)
        return fmt.Errorf("traffic switch failed: %v", err)
    }

    // Phase 5: Monitor new environment
    fmt.Printf("Phase 5: Monitoring new environment\n")

    monitor := do.startPostDeploymentMonitoring(greenEnv, config)
    defer monitor.Stop()

    // Wait for stabilization period
    stabilizationPeriod := 10 * time.Minute
    if err := do.monitorStabilization(greenEnv, stabilizationPeriod, config.PerformanceThresholds); err != nil {
        // Auto-rollback if enabled
        if config.AutoRollbackEnabled {
            fmt.Printf("Performance degradation detected, executing auto-rollback\n")
            if rollbackErr := do.rollback.ExecuteRollback(switchHandle); rollbackErr != nil {
                return fmt.Errorf("rollback failed after performance issue: %v (original error: %v)", rollbackErr, err)
            }
        }
        return fmt.Errorf("deployment monitoring failed: %v", err)
    }

    // Phase 6: Cleanup old environment
    fmt.Printf("Phase 6: Cleaning up Blue environment\n")

    if err := do.cleanupBlueEnvironment(); err != nil {
        // Log but don't fail deployment
        fmt.Printf("Warning: Blue environment cleanup failed: %v\n", err)
    }

    do.metrics.RecordSuccessfulDeployment(deployment)
    do.notifications.SendDeploymentSuccess(deployment, perfResults)

    return nil
}

// Canary deployment with gradual traffic increase
func (do *DeploymentOrchestrator) ExecuteCanaryDeployment(version string, config DeploymentConfig) error {
    deployment := &CanaryDeployment{
        Version:      version,
        Config:       config,
        Orchestrator: do,
        StartTime:    time.Now(),
    }

    // Deploy canary version
    canaryEnv, err := do.deployCanaryEnvironment(version, config)
    if err != nil {
        return fmt.Errorf("canary deployment failed: %v", err)
    }

    // Health check canary
    if err := do.healthCheckEnvironment(canaryEnv, config); err != nil {
        do.cleanupCanaryEnvironment(canaryEnv)
        return fmt.Errorf("canary health check failed: %v", err)
    }

    // Gradual traffic increase
    trafficSteps := []int{1, 5, 10, 25, 50, 100} // Percentage of traffic

    for _, trafficPercent := range trafficSteps {
        fmt.Printf("Routing %d%% traffic to canary\n", trafficPercent)

        // Update load balancer
        if err := do.loadBalancer.SetCanaryTraffic(canaryEnv, trafficPercent); err != nil {
            return fmt.Errorf("failed to route %d%% traffic to canary: %v", trafficPercent, err)
        }

        // Monitor for stability period
        monitorDuration := config.RolloutDuration / time.Duration(len(trafficSteps))

        metrics, err := do.monitorCanaryPerformance(canaryEnv, monitorDuration, config.PerformanceThresholds)
        if err != nil {
            // Rollback on performance issues
            if config.AutoRollbackEnabled {
                fmt.Printf("Canary performance issue detected, rolling back\n")
                do.rollback.RollbackCanary(canaryEnv)
            }
            return fmt.Errorf("canary monitoring failed at %d%% traffic: %v", trafficPercent, err)
        }

        // Compare canary vs production metrics
        comparison := do.compareCanaryMetrics(metrics)
        if !comparison.IsAcceptable {
            if config.AutoRollbackEnabled {
                do.rollback.RollbackCanary(canaryEnv)
            }
            return fmt.Errorf("canary performance regression detected: %s", comparison.Issues)
        }

        fmt.Printf("Canary stable at %d%% traffic\n", trafficPercent)
    }

    // Promote canary to production
    if err := do.promoteCanaryToProduction(canaryEnv); err != nil {
        return fmt.Errorf("canary promotion failed: %v", err)
    }

    do.metrics.RecordSuccessfulDeployment(deployment)
    return nil
}

// Performance-aware rolling deployment
func (do *DeploymentOrchestrator) ExecuteRollingDeployment(version string, config DeploymentConfig) error {
    deployment := &RollingDeployment{
        Version:      version,
        Config:       config,
        Orchestrator: do,
        StartTime:    time.Now(),
    }

    // Get current instance list
    instances, err := do.getCurrentInstances()
    if err != nil {
        return fmt.Errorf("failed to get current instances: %v", err)
    }

    // Rolling update with performance monitoring
    batchSize := max(1, len(instances)/5) // Update 20% at a time

    for i := 0; i < len(instances); i += batchSize {
        end := min(i+batchSize, len(instances))
        batch := instances[i:end]

        fmt.Printf("Updating batch %d-%d of %d instances\n", i+1, end, len(instances))

        // Update batch
        if err := do.updateInstanceBatch(batch, version, config); err != nil {
            return fmt.Errorf("batch update failed: %v", err)
        }

        // Wait for batch to stabilize
        if err := do.waitForBatchStabilization(batch, config); err != nil {
            if config.AutoRollbackEnabled {
                do.rollback.RollbackBatch(batch)
            }
            return fmt.Errorf("batch stabilization failed: %v", err)
        }

        // Validate overall system performance
        systemMetrics, err := do.validateSystemPerformance(config.PerformanceThresholds)
        if err != nil {
            if config.AutoRollbackEnabled {
                do.rollback.RollbackDeployment(deployment)
            }
            return fmt.Errorf("system performance validation failed: %v", err)
        }

        do.metrics.RecordBatchDeployment(batch, systemMetrics)
    }

    do.metrics.RecordSuccessfulDeployment(deployment)
    return nil
}

// Health checking with performance validation
type HealthChecker struct {
    httpClient    *http.Client
    checks        []HealthCheck
    retryPolicy   *RetryPolicy
}

type HealthCheck struct {
    Name        string
    Endpoint    string
    Method      string
    Timeout     time.Duration
    Expected    HealthExpectation
    Validator   func(*http.Response) error
}

type HealthExpectation struct {
    StatusCode      int           `yaml:"status_code"`
    MaxResponseTime time.Duration `yaml:"max_response_time"`
    RequiredHeaders map[string]string `yaml:"required_headers"`
    BodyContains    []string      `yaml:"body_contains"`
}

func (hc *HealthChecker) CheckEnvironmentHealth(env *Environment, timeout time.Duration) error {
    ctx, cancel := context.WithTimeout(context.Background(), timeout)
    defer cancel()

    var wg sync.WaitGroup
    errorChan := make(chan error, len(hc.checks))

    for _, check := range hc.checks {
        wg.Add(1)
        go func(check HealthCheck) {
            defer wg.Done()

            if err := hc.executeHealthCheck(ctx, env, check); err != nil {
                errorChan <- fmt.Errorf("health check %s failed: %v", check.Name, err)
            }
        }(check)
    }

    // Wait for all checks to complete
    go func() {
        wg.Wait()
        close(errorChan)
    }()

    // Collect any errors
    var errors []string
    for err := range errorChan {
        errors = append(errors, err.Error())
    }

    if len(errors) > 0 {
        return fmt.Errorf("health checks failed: %s", strings.Join(errors, "; "))
    }

    return nil
}

func (hc *HealthChecker) executeHealthCheck(ctx context.Context, env *Environment, check HealthCheck) error {
    url := fmt.Sprintf("%s%s", env.BaseURL, check.Endpoint)

    // Execute with retry policy
    return hc.retryPolicy.Execute(func() error {
        start := time.Now()

        req, err := http.NewRequestWithContext(ctx, check.Method, url, nil)
        if err != nil {
            return err
        }

        resp, err := hc.httpClient.Do(req)
        if err != nil {
            return err
        }
        defer resp.Body.Close()

        responseTime := time.Since(start)

        // Validate response
        if resp.StatusCode != check.Expected.StatusCode {
            return fmt.Errorf("unexpected status code: got %d, expected %d", 
                            resp.StatusCode, check.Expected.StatusCode)
        }

        if responseTime > check.Expected.MaxResponseTime {
            return fmt.Errorf("response time %v exceeds threshold %v", 
                            responseTime, check.Expected.MaxResponseTime)
        }

        // Custom validation
        if check.Validator != nil {
            if err := check.Validator(resp); err != nil {
                return err
            }
        }

        return nil
    })
}

// Performance validation during deployment
type PerformanceValidator struct {
    monitor     *PerformanceMonitor
    comparator  *PerformanceComparator
    thresholds  *PerformanceThresholds
}

func (pv *PerformanceValidator) ValidateDeploymentPerformance(env *Environment, thresholds PerformanceThresholds) (*PerformanceValidationResult, error) {
    // Collect performance metrics
    metrics, err := pv.monitor.CollectMetrics(env, 5*time.Minute)
    if err != nil {
        return nil, fmt.Errorf("failed to collect metrics: %v", err)
    }

    // Validate against thresholds
    violations := pv.validateThresholds(metrics, thresholds)

    // Compare with baseline if available
    var comparison *PerformanceComparison
    if baseline := pv.getBaseline(env); baseline != nil {
        comparison = pv.comparator.Compare(metrics, baseline)
    }

    result := &PerformanceValidationResult{
        Metrics:     metrics,
        Violations:  violations,
        Comparison:  comparison,
        Passed:      len(violations) == 0 && (comparison == nil || comparison.IsAcceptable),
        Timestamp:   time.Now(),
    }

    return result, nil
}

func (pv *PerformanceValidator) validateThresholds(metrics *PerformanceMetrics, thresholds PerformanceThresholds) []ThresholdViolation {
    var violations []ThresholdViolation

    if metrics.LatencyP95 > thresholds.MaxLatencyP95 {
        violations = append(violations, ThresholdViolation{
            Metric:    "latency_p95",
            Current:   metrics.LatencyP95,
            Threshold: thresholds.MaxLatencyP95,
            Severity:  "critical",
        })
    }

    if metrics.ThroughputRPS < thresholds.MinThroughput {
        violations = append(violations, ThresholdViolation{
            Metric:    "throughput",
            Current:   metrics.ThroughputRPS,
            Threshold: thresholds.MinThroughput,
            Severity:  "critical",
        })
    }

    if metrics.ErrorRate > thresholds.MaxErrorRate {
        violations = append(violations, ThresholdViolation{
            Metric:    "error_rate",
            Current:   metrics.ErrorRate,
            Threshold: thresholds.MaxErrorRate,
            Severity:  "critical",
        })
    }

    if metrics.MemoryUsage > thresholds.MaxMemoryUsage {
        violations = append(violations, ThresholdViolation{
            Metric:    "memory_usage",
            Current:   metrics.MemoryUsage,
            Threshold: thresholds.MaxMemoryUsage,
            Severity:  "warning",
        })
    }

    if metrics.CPUUsage > thresholds.MaxCPUUsage {
        violations = append(violations, ThresholdViolation{
            Metric:    "cpu_usage", 
            Current:   metrics.CPUUsage,
            Threshold: thresholds.MaxCPUUsage,
            Severity:  "warning",
        })
    }

    return violations
}

// Rollback management
type RollbackManager struct {
    versions    *VersionManager
    loadBalancer *LoadBalancer
    orchestrator *DeploymentOrchestrator
    notifications *NotificationService
}

func (rm *RollbackManager) ExecuteAutomaticRollback(trigger RollbackTrigger) error {
    fmt.Printf("Executing automatic rollback due to: %s\n", trigger.Reason)

    // Get previous version
    previousVersion, err := rm.versions.GetPreviousVersion()
    if err != nil {
        return fmt.Errorf("failed to get previous version: %v", err)
    }

    // Execute fast rollback
    start := time.Now()

    switch trigger.Type {
    case PerformanceRollback:
        err = rm.performanceRollback(previousVersion, trigger)
    case HealthCheckRollback:
        err = rm.healthCheckRollback(previousVersion, trigger)
    case ErrorRateRollback:
        err = rm.errorRateRollback(previousVersion, trigger)
    default:
        err = rm.genericRollback(previousVersion, trigger)
    }

    duration := time.Since(start)

    if err != nil {
        rm.notifications.SendRollbackFailure(trigger, err)
        return fmt.Errorf("rollback failed: %v", err)
    }

    rm.notifications.SendRollbackSuccess(trigger, duration)
    fmt.Printf("Rollback completed in %v\n", duration)

    return nil
}

func (rm *RollbackManager) performanceRollback(version string, trigger RollbackTrigger) error {
    // Immediate traffic switch to previous version
    if err := rm.loadBalancer.SwitchToVersion(version); err != nil {
        return err
    }

    // Validate rollback success
    if err := rm.validateRollbackSuccess(version); err != nil {
        return fmt.Errorf("rollback validation failed: %v", err)
    }

    return nil
}

func (rm *RollbackManager) validateRollbackSuccess(version string) error {
    // Wait for traffic switch to take effect
    time.Sleep(30 * time.Second)

    // Check that performance has recovered
    env := rm.getEnvironmentForVersion(version)

    validator := NewPerformanceValidator()
    result, err := validator.ValidateDeploymentPerformance(env, DefaultPerformanceThresholds())
    if err != nil {
        return err
    }

    if !result.Passed {
        return fmt.Errorf("rollback did not restore performance: %v", result.Violations)
    }

    return nil
}

Real-Time Performance Monitoring

Comprehensive Monitoring Infrastructure

// Advanced performance monitoring system
type PerformanceMonitoringSystem struct {
    collectors  []MetricsCollector
    processors  []MetricsProcessor
    alerters    []AlertManager
    dashboards  []Dashboard
    storage     MetricsStorage
    analyzer    *RealTimeAnalyzer
}

type MetricsCollector interface {
    Collect(ctx context.Context) ([]Metric, error)
    GetMetricTypes() []string
    GetCollectionInterval() time.Duration
}

// Application performance metrics collector
type ApplicationMetricsCollector struct {
    httpClient  *http.Client
    endpoints   []string
    interval    time.Duration
}

func (amc *ApplicationMetricsCollector) Collect(ctx context.Context) ([]Metric, error) {
    var metrics []Metric
    timestamp := time.Now()

    for _, endpoint := range amc.endpoints {
        // Collect runtime metrics
        runtimeMetrics, err := amc.collectRuntimeMetrics(endpoint)
        if err != nil {
            continue // Log error but continue with other endpoints
        }

        // Collect HTTP metrics
        httpMetrics, err := amc.collectHTTPMetrics(endpoint)
        if err != nil {
            continue
        }

        // Collect custom application metrics
        appMetrics, err := amc.collectApplicationMetrics(endpoint)
        if err != nil {
            continue
        }

        // Combine all metrics
        endpointMetrics := append(runtimeMetrics, httpMetrics...)
        endpointMetrics = append(endpointMetrics, appMetrics...)

        // Add metadata
        for _, metric := range endpointMetrics {
            metric.Timestamp = timestamp
            metric.Labels["endpoint"] = endpoint
            metric.Labels["collector"] = "application"
        }

        metrics = append(metrics, endpointMetrics...)
    }

    return metrics, nil
}

func (amc *ApplicationMetricsCollector) collectRuntimeMetrics(endpoint string) ([]Metric, error) {
    // Get Go runtime metrics via pprof or custom endpoint
    resp, err := amc.httpClient.Get(endpoint + "/debug/vars")
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()

    var data map[string]interface{}
    if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
        return nil, err
    }

    var metrics []Metric

    // Memory metrics
    if memStats, ok := data["memstats"].(map[string]interface{}); ok {
        metrics = append(metrics, []Metric{
            {
                Name:   "go_memory_heap_bytes",
                Value:  memStats["HeapInuse"].(float64),
                Type:   "gauge",
                Labels: map[string]string{"type": "heap_inuse"},
            },
            {
                Name:   "go_memory_heap_bytes",
                Value:  memStats["HeapSys"].(float64),
                Type:   "gauge", 
                Labels: map[string]string{"type": "heap_sys"},
            },
            {
                Name:   "go_memory_stack_bytes",
                Value:  memStats["StackInuse"].(float64),
                Type:   "gauge",
                Labels: map[string]string{"type": "stack_inuse"},
            },
            {
                Name:   "go_gc_duration_seconds",
                Value:  memStats["PauseNs"].(float64) / 1e9,
                Type:   "gauge",
                Labels: map[string]string{},
            },
        }...)
    }

    // Goroutine metrics
    if goroutines, ok := data["goroutines"].(float64); ok {
        metrics = append(metrics, Metric{
            Name:   "go_goroutines",
            Value:  goroutines,
            Type:   "gauge",
            Labels: map[string]string{},
        })
    }

    return metrics, nil
}

// Infrastructure metrics collector
type InfrastructureMetricsCollector struct {
    nodeExporter *NodeExporter
    k8sClient    *kubernetes.Clientset
    interval     time.Duration
}

func (imc *InfrastructureMetricsCollector) Collect(ctx context.Context) ([]Metric, error) {
    var metrics []Metric

    // CPU metrics
    cpuMetrics, err := imc.collectCPUMetrics()
    if err == nil {
        metrics = append(metrics, cpuMetrics...)
    }

    // Memory metrics
    memoryMetrics, err := imc.collectMemoryMetrics()
    if err == nil {
        metrics = append(metrics, memoryMetrics...)
    }

    // Network metrics
    networkMetrics, err := imc.collectNetworkMetrics()
    if err == nil {
        metrics = append(metrics, networkMetrics...)
    }

    // Disk metrics
    diskMetrics, err := imc.collectDiskMetrics()
    if err == nil {
        metrics = append(metrics, diskMetrics...)
    }

    // Kubernetes metrics if available
    if imc.k8sClient != nil {
        k8sMetrics, err := imc.collectKubernetesMetrics(ctx)
        if err == nil {
            metrics = append(metrics, k8sMetrics...)
        }
    }

    return metrics, nil
}

// Real-time performance analyzer
type RealTimeAnalyzer struct {
    thresholds      *AlertThresholds
    anomalyDetector *AnomalyDetector
    trendAnalyzer   *TrendAnalyzer
    correlator      *MetricsCorrelator
    predictor       *PerformancePredictor
}

type AlertThresholds struct {
    ResponseTime  ThresholdConfig `yaml:"response_time"`
    Throughput    ThresholdConfig `yaml:"throughput"`
    ErrorRate     ThresholdConfig `yaml:"error_rate"`
    MemoryUsage   ThresholdConfig `yaml:"memory_usage"`
    CPUUsage      ThresholdConfig `yaml:"cpu_usage"`
    DiskUsage     ThresholdConfig `yaml:"disk_usage"`
}

type ThresholdConfig struct {
    Warning   float64 `yaml:"warning"`
    Critical  float64 `yaml:"critical"`
    Duration  time.Duration `yaml:"duration"` // How long threshold must be exceeded
}

func (rta *RealTimeAnalyzer) AnalyzeMetrics(metrics []Metric) (*AnalysisResult, error) {
    result := &AnalysisResult{
        Timestamp: time.Now(),
        Metrics:   metrics,
    }

    // Threshold analysis
    thresholdAlerts := rta.checkThresholds(metrics)
    result.ThresholdAlerts = thresholdAlerts

    // Anomaly detection
    anomalies := rta.anomalyDetector.DetectAnomalies(metrics)
    result.Anomalies = anomalies

    // Trend analysis
    trends := rta.trendAnalyzer.AnalyzeTrends(metrics)
    result.Trends = trends

    // Correlation analysis
    correlations := rta.correlator.FindCorrelations(metrics)
    result.Correlations = correlations

    // Performance prediction
    predictions := rta.predictor.PredictPerformance(metrics)
    result.Predictions = predictions

    // Overall health score
    result.HealthScore = rta.calculateHealthScore(result)

    return result, nil
}

func (rta *RealTimeAnalyzer) checkThresholds(metrics []Metric) []ThresholdAlert {
    var alerts []ThresholdAlert

    for _, metric := range metrics {
        threshold := rta.getThresholdForMetric(metric.Name)
        if threshold == nil {
            continue
        }

        severity := rta.evaluateThreshold(metric.Value, *threshold)
        if severity != None {
            alerts = append(alerts, ThresholdAlert{
                MetricName: metric.Name,
                Value:      metric.Value,
                Threshold:  *threshold,
                Severity:   severity,
                Timestamp:  metric.Timestamp,
                Labels:     metric.Labels,
            })
        }
    }

    return alerts
}

// Anomaly detection using statistical methods
type AnomalyDetector struct {
    models    map[string]*AnomalyModel
    window    time.Duration
    sensitivity float64
}

type AnomalyModel struct {
    MetricName     string
    Mean           float64
    StdDev         float64
    Seasonality    *SeasonalPattern
    LastUpdate     time.Time
    DataPoints     []float64
}

func (ad *AnomalyDetector) DetectAnomalies(metrics []Metric) []Anomaly {
    var anomalies []Anomaly

    for _, metric := range metrics {
        model := ad.getOrCreateModel(metric.Name)

        // Update model with new data point
        model.addDataPoint(metric.Value)

        // Check for anomaly
        if anomaly := ad.checkAnomaly(metric, model); anomaly != nil {
            anomalies = append(anomalies, *anomaly)
        }
    }

    return anomalies
}

func (ad *AnomalyDetector) checkAnomaly(metric Metric, model *AnomalyModel) *Anomaly {
    // Z-score based anomaly detection
    zScore := math.Abs((metric.Value - model.Mean) / model.StdDev)

    threshold := 3.0 * ad.sensitivity // Configurable sensitivity

    if zScore > threshold {
        return &Anomaly{
            MetricName:  metric.Name,
            Value:       metric.Value,
            Expected:    model.Mean,
            ZScore:      zScore,
            Timestamp:   metric.Timestamp,
            Severity:    ad.calculateAnomalySeverity(zScore),
            Labels:      metric.Labels,
        }
    }

    return nil
}

// Performance prediction using time series forecasting
type PerformancePredictor struct {
    models     map[string]*PredictionModel
    horizon    time.Duration
    confidence float64
}

type PredictionModel struct {
    MetricName   string
    Algorithm    string // "linear", "arima", "lstm"
    Parameters   map[string]float64
    Accuracy     float64
    LastTrained  time.Time
}

func (pp *PerformancePredictor) PredictPerformance(metrics []Metric) []PerformancePrediction {
    var predictions []PerformancePrediction

    for _, metric := range metrics {
        model := pp.getOrCreateModel(metric.Name)

        // Update model if needed
        if time.Since(model.LastTrained) > time.Hour {
            pp.retrainModel(model, metric.Name)
        }

        // Generate prediction
        prediction := pp.generatePrediction(metric, model)
        if prediction != nil {
            predictions = append(predictions, *prediction)
        }
    }

    return predictions
}

func (pp *PerformancePredictor) generatePrediction(metric Metric, model *PredictionModel) *PerformancePrediction {
    // Simple linear prediction for demonstration
    // In production, use more sophisticated algorithms

    historyData := pp.getHistoricalData(metric.Name, 24*time.Hour)
    if len(historyData) < 10 {
        return nil // Insufficient data
    }

    // Calculate trend
    trend := pp.calculateTrend(historyData)

    // Project into future
    futureValue := metric.Value + (trend * float64(pp.horizon.Hours()))

    return &PerformancePrediction{
        MetricName:     metric.Name,
        CurrentValue:   metric.Value,
        PredictedValue: futureValue,
        Confidence:     model.Accuracy,
        Horizon:        pp.horizon,
        Timestamp:      time.Now(),
        Algorithm:      model.Algorithm,
    }
}

// Alert management and notification
type AlertManager struct {
    rules        []AlertRule
    channels     []NotificationChannel
    escalation   *EscalationPolicy
    suppression  *AlertSuppression
}

type AlertRule struct {
    Name        string
    Condition   string        // PromQL-like expression
    Duration    time.Duration // How long condition must be true
    Severity    AlertSeverity
    Labels      map[string]string
    Annotations map[string]string
}

type NotificationChannel interface {
    Send(alert Alert) error
    GetType() string
    IsHealthy() bool
}

// Slack notification channel
type SlackChannel struct {
    webhookURL string
    channel    string
    username   string
    httpClient *http.Client
}

func (sc *SlackChannel) Send(alert Alert) error {
    message := SlackMessage{
        Channel:  sc.channel,
        Username: sc.username,
        Attachments: []SlackAttachment{
            {
                Color:  sc.getSeverityColor(alert.Severity),
                Title:  alert.Summary,
                Text:   alert.Description,
                Fields: sc.buildFields(alert),
                Footer: "Performance Monitoring",
                Ts:     alert.Timestamp.Unix(),
            },
        },
    }

    payload, err := json.Marshal(message)
    if err != nil {
        return err
    }

    resp, err := sc.httpClient.Post(sc.webhookURL, "application/json", bytes.NewBuffer(payload))
    if err != nil {
        return err
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK {
        return fmt.Errorf("slack notification failed with status: %d", resp.StatusCode)
    }

    return nil
}

// PagerDuty notification channel
type PagerDutyChannel struct {
    integrationKey string
    httpClient     *http.Client
}

func (pd *PagerDutyChannel) Send(alert Alert) error {
    event := PagerDutyEvent{
        RoutingKey:  pd.integrationKey,
        EventAction: "trigger",
        Payload: PagerDutyPayload{
            Summary:   alert.Summary,
            Source:    alert.Source,
            Severity:  string(alert.Severity),
            Timestamp: alert.Timestamp.Format(time.RFC3339),
            CustomDetails: map[string]interface{}{
                "description": alert.Description,
                "labels":      alert.Labels,
                "annotations": alert.Annotations,
            },
        },
    }

    payload, err := json.Marshal(event)
    if err != nil {
        return err
    }

    resp, err := pd.httpClient.Post("https://events.pagerduty.com/v2/enqueue", 
                                   "application/json", bytes.NewBuffer(payload))
    if err != nil {
        return err
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusAccepted {
        return fmt.Errorf("pagerduty notification failed with status: %d", resp.StatusCode)
    }

    return nil
}

// Alert escalation policy
type EscalationPolicy struct {
    levels []EscalationLevel
}

type EscalationLevel struct {
    Duration time.Duration
    Channels []NotificationChannel
    OnCall   []string
}

func (ep *EscalationPolicy) ProcessAlert(alert Alert) error {
    for i, level := range ep.levels {
        fmt.Printf("Escalation level %d: %v\n", i+1, level.Duration)

        // Send to all channels at this level
        for _, channel := range level.Channels {
            if err := channel.Send(alert); err != nil {
                fmt.Printf("Failed to send alert via %s: %v\n", channel.GetType(), err)
            }
        }

        // Wait for acknowledgment or escalation timeout
        select {
        case <-time.After(level.Duration):
            // Continue to next level
            continue
        case <-ep.waitForAcknowledgment(alert):
            // Alert acknowledged, stop escalation
            return nil
        }
    }

    return fmt.Errorf("alert not acknowledged after all escalation levels")
}

func (ep *EscalationPolicy) waitForAcknowledgment(alert Alert) <-chan struct{} {
    // Implementation would check external system for acknowledgment
    // This is a simplified placeholder
    ackChan := make(chan struct{})
    go func() {
        // In real implementation, poll alerting system for acknowledgment
        time.Sleep(30 * time.Second) // Simulate acknowledgment
        close(ackChan)
    }()
    return ackChan
}

This comprehensive deployment and monitoring framework ensures that high-performance Go applications can be safely deployed to production with sophisticated performance validation, real-time monitoring, and automated incident response capabilities.

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