Feature: Add Prometheus exporter (#505)

internal/prometheus/metrics.go

@@ -0,0 +1,188 @@
+// Package prometheus provides Prometheus metrics for Mailpit
+package prometheus
+
+import (
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/axllent/mailpit/config"
+	"github.com/axllent/mailpit/internal/logger"
+	"github.com/axllent/mailpit/internal/stats"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	// Registry is the Prometheus registry for Mailpit metrics
+	Registry = prometheus.NewRegistry()
+
+	// Metrics
+	totalMessages    prometheus.Gauge
+	unreadMessages   prometheus.Gauge
+	databaseSize     prometheus.Gauge
+	messagesDeleted  prometheus.Counter
+	smtpAccepted     prometheus.Counter
+	smtpRejected     prometheus.Counter
+	smtpIgnored      prometheus.Counter
+	smtpAcceptedSize prometheus.Counter
+	uptime           prometheus.Gauge
+	memoryUsage      prometheus.Gauge
+	tagCounters      *prometheus.GaugeVec
+)
+
+// InitMetrics initializes all Prometheus metrics
+func InitMetrics() {
+	// Create metrics
+	totalMessages = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "mailpit_messages",
+		Help: "Total number of messages in the database",
+	})
+
+	unreadMessages = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "mailpit_messages_unread",
+		Help: "Number of unread messages in the database",
+	})
+
+	databaseSize = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "mailpit_database_size_bytes",
+		Help: "Size of the database in bytes",
+	})
+
+	messagesDeleted = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "mailpit_messages_deleted_total",
+		Help: "Total number of messages deleted",
+	})
+
+	smtpAccepted = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "mailpit_smtp_accepted_total",
+		Help: "Total number of SMTP messages accepted",
+	})
+
+	smtpRejected = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "mailpit_smtp_rejected_total",
+		Help: "Total number of SMTP messages rejected",
+	})
+
+	smtpIgnored = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "mailpit_smtp_ignored_total",
+		Help: "Total number of SMTP messages ignored (duplicates)",
+	})
+
+	smtpAcceptedSize = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "mailpit_smtp_accepted_size_bytes_total",
+		Help: "Total size of accepted SMTP messages in bytes",
+	})
+
+	uptime = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "mailpit_uptime_seconds",
+		Help: "Uptime of Mailpit in seconds",
+	})
+
+	memoryUsage = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "mailpit_memory_usage_bytes",
+		Help: "Memory usage in bytes",
+	})
+
+	tagCounters = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "mailpit_tag_messages",
+			Help: "Number of messages per tag",
+		},
+		[]string{"tag"},
+	)
+
+	// Register metrics
+	Registry.MustRegister(totalMessages)
+	Registry.MustRegister(unreadMessages)
+	Registry.MustRegister(databaseSize)
+	Registry.MustRegister(messagesDeleted)
+	Registry.MustRegister(smtpAccepted)
+	Registry.MustRegister(smtpRejected)
+	Registry.MustRegister(smtpIgnored)
+	Registry.MustRegister(smtpAcceptedSize)
+	Registry.MustRegister(uptime)
+	Registry.MustRegister(memoryUsage)
+	Registry.MustRegister(tagCounters)
+}
+
+// UpdateMetrics updates all metrics with current values
+func UpdateMetrics() {
+	info := stats.Load()
+
+	totalMessages.Set(float64(info.Messages))
+	unreadMessages.Set(float64(info.Unread))
+	databaseSize.Set(float64(info.DatabaseSize))
+	messagesDeleted.Add(float64(info.RuntimeStats.MessagesDeleted))
+	smtpAccepted.Add(float64(info.RuntimeStats.SMTPAccepted))
+	smtpRejected.Add(float64(info.RuntimeStats.SMTPRejected))
+	smtpIgnored.Add(float64(info.RuntimeStats.SMTPIgnored))
+	smtpAcceptedSize.Add(float64(info.RuntimeStats.SMTPAcceptedSize))
+	uptime.Set(float64(info.RuntimeStats.Uptime))
+	memoryUsage.Set(float64(info.RuntimeStats.Memory))
+
+	// Reset tag counters
+	tagCounters.Reset()
+
+	// Update tag counters
+	for tag, count := range info.Tags {
+		tagCounters.WithLabelValues(tag).Set(float64(count))
+	}
+}
+
+// Returns the Prometheus handler & disables double compression in middleware
+func GetHandler() http.Handler {
+	return promhttp.HandlerFor(Registry, promhttp.HandlerOpts{
+		DisableCompression: true,
+	})
+}
+
+// StartUpdater starts the periodic metrics update routine
+func StartUpdater() {
+	InitMetrics()
+	UpdateMetrics()
+
+	// Start periodic updates
+	go func() {
+		ticker := time.NewTicker(15 * time.Second)
+		defer ticker.Stop()
+
+		for range ticker.C {
+			UpdateMetrics()
+		}
+	}()
+}
+
+// StartSeparateServer starts a separate HTTP server for Prometheus metrics
+func StartSeparateServer() {
+	StartUpdater()
+
+	logger.Log().Infof("[prometheus] metrics server listening on %s", config.PrometheusListen)
+
+	// Create a dedicated mux for the metrics server
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.HandlerFor(Registry, promhttp.HandlerOpts{}))
+
+	// Create a dedicated server instance
+	server := &http.Server{
+		Addr:    config.PrometheusListen,
+		Handler: mux,
+	}
+
+	// Start HTTP server
+	if err := server.ListenAndServe(); err != nil {
+		logger.Log().Errorf("[prometheus] metrics server error: %s", err.Error())
+	}
+}
+
+// GetMode returns the Prometheus run mode
+func GetMode() string {
+	mode := strings.ToLower(strings.TrimSpace(config.PrometheusListen))
+	if mode == "false" {
+		return "disabled"
+	}
+	if mode == "true" {
+		return "integrated"
+	}
+	return "separate"
+}