feat: add embedded systemd installer and Prometheus metrics

Systemd Integration: - New 'dbbackup install' command creates service/timer units - Supports single-database and cluster backup modes - Automatic dbbackup user/group creation with proper permissions - Hardened service units with security features - Template units with configurable OnCalendar schedules - 'dbbackup uninstall' for clean removal Prometheus Metrics: - 'dbbackup metrics export' for textfile collector format - 'dbbackup metrics serve' runs HTTP exporter on port 9399 - Metrics: last_success_timestamp, rpo_seconds, backup_total, etc. - Integration with node_exporter textfile collector - --with-metrics flag during install Technical: - Systemd templates embedded with //go:embed - Service units include ReadWritePaths, OOMScoreAdjust - Metrics exporter caches with 30s TTL - Graceful shutdown on SIGTERM
2026-01-07 11:18:09 +01:00
parent 120ee33e3b
commit 7e32a0369d
12 changed files with 1641 additions and 0 deletions
--- a/internal/prometheus/exporter.go
+++ b/internal/prometheus/exporter.go
@@ -0,0 +1,174 @@
+// Package prometheus provides Prometheus metrics for dbbackup
+package prometheus
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"sync"
+	"time"
+
+	"dbbackup/internal/catalog"
+	"dbbackup/internal/logger"
+)
+
+// Exporter provides an HTTP endpoint for Prometheus metrics
+type Exporter struct {
+	log      logger.Logger
+	catalog  catalog.Catalog
+	instance string
+	port     int
+
+	mu          sync.RWMutex
+	cachedData  string
+	lastRefresh time.Time
+	refreshTTL  time.Duration
+}
+
+// NewExporter creates a new Prometheus exporter
+func NewExporter(log logger.Logger, cat catalog.Catalog, instance string, port int) *Exporter {
+	return &Exporter{
+		log:        log,
+		catalog:    cat,
+		instance:   instance,
+		port:       port,
+		refreshTTL: 30 * time.Second,
+	}
+}
+
+// Serve starts the HTTP server and blocks until context is cancelled
+func (e *Exporter) Serve(ctx context.Context) error {
+	mux := http.NewServeMux()
+
+	// /metrics endpoint
+	mux.HandleFunc("/metrics", e.handleMetrics)
+
+	// /health endpoint
+	mux.HandleFunc("/health", e.handleHealth)
+
+	// / root with info
+	mux.HandleFunc("/", e.handleRoot)
+
+	addr := fmt.Sprintf(":%d", e.port)
+	srv := &http.Server{
+		Addr:         addr,
+		Handler:      mux,
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 30 * time.Second,
+		IdleTimeout:  60 * time.Second,
+	}
+
+	// Start refresh goroutine
+	go e.refreshLoop(ctx)
+
+	// Graceful shutdown
+	go func() {
+		<-ctx.Done()
+		e.log.Info("Shutting down metrics server...")
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := srv.Shutdown(shutdownCtx); err != nil {
+			e.log.Error("Server shutdown error", "error", err)
+		}
+	}()
+
+	e.log.Info("Starting Prometheus metrics server", "addr", addr)
+	if err := srv.ListenAndServe(); err != http.ErrServerClosed {
+		return fmt.Errorf("server error: %w", err)
+	}
+
+	return nil
+}
+
+// handleMetrics handles /metrics endpoint
+func (e *Exporter) handleMetrics(w http.ResponseWriter, r *http.Request) {
+	e.mu.RLock()
+	data := e.cachedData
+	e.mu.RUnlock()
+
+	if data == "" {
+		// Force refresh if cache is empty
+		if err := e.refresh(); err != nil {
+			http.Error(w, "Failed to collect metrics", http.StatusInternalServerError)
+			return
+		}
+		e.mu.RLock()
+		data = e.cachedData
+		e.mu.RUnlock()
+	}
+
+	w.Header().Set("Content-Type", "text/plain; version=0.0.4; charset=utf-8")
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte(data))
+}
+
+// handleHealth handles /health endpoint
+func (e *Exporter) handleHealth(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte(`{"status":"ok","service":"dbbackup-exporter"}`))
+}
+
+// handleRoot handles / endpoint
+func (e *Exporter) handleRoot(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path != "/" {
+		http.NotFound(w, r)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/html")
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte(`<!DOCTYPE html>
+<html>
+<head>
+  <title>DBBackup Exporter</title>
+</head>
+<body>
+  <h1>DBBackup Prometheus Exporter</h1>
+  <p>This is a Prometheus metrics exporter for DBBackup.</p>
+  <ul>
+    <li><a href="/metrics">/metrics</a> - Prometheus metrics</li>
+    <li><a href="/health">/health</a> - Health check</li>
+  </ul>
+</body>
+</html>`))
+}
+
+// refreshLoop periodically refreshes the metrics cache
+func (e *Exporter) refreshLoop(ctx context.Context) {
+	ticker := time.NewTicker(e.refreshTTL)
+	defer ticker.Stop()
+
+	// Initial refresh
+	if err := e.refresh(); err != nil {
+		e.log.Error("Initial metrics refresh failed", "error", err)
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			if err := e.refresh(); err != nil {
+				e.log.Error("Metrics refresh failed", "error", err)
+			}
+		}
+	}
+}
+
+// refresh updates the cached metrics
+func (e *Exporter) refresh() error {
+	writer := NewMetricsWriter(e.log, e.catalog, e.instance)
+	data, err := writer.GenerateMetricsString()
+	if err != nil {
+		return err
+	}
+
+	e.mu.Lock()
+	e.cachedData = data
+	e.lastRefresh = time.Now()
+	e.mu.Unlock()
+
+	e.log.Debug("Refreshed metrics cache")
+	return nil
+}