feat(db): implement PostgreSQL monitoring and maintenance features

Added PostgreSQL monitoring and maintenance capabilities to the API, including new endpoints for instance-level metrics, maintenance operations, and job scheduling. Updated the HTTP API to support PostgreSQL monitoring routes and integrated a background scheduler for metrics collection. Enhanced the CLI with database commands for maintenance tasks. Updated documentation to reflect these changes.

internal/httpapi/routes_postgres_monitoring.go

@@ -0,0 +1,130 @@
+package httpapi
+
+import (
+	"context"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+func (s *Server) registerPostgresMonitoringRoutes(m *http.ServeMux) {
+	m.HandleFunc("GET /monitoring/postgres/overview", s.handlePostgresOverview)
+	m.HandleFunc("GET /monitoring/postgres/queries", s.handlePostgresQueries)
+	m.HandleFunc("GET /monitoring/postgres/locks", s.handlePostgresLocks)
+	m.HandleFunc("GET /monitoring/postgres/tables", s.handlePostgresTables)
+	m.HandleFunc("GET /monitoring/postgres/recommendations", s.handlePostgresRecommendations)
+	m.HandleFunc("GET /monitoring/correlation", s.handleMonitoringCorrelation)
+}
+
+func (s *Server) requirePostgres(w http.ResponseWriter) bool {
+	if s.pgMonitor == nil {
+		writeProblem(w, http.StatusServiceUnavailable, "Unavailable", "postgresql backend required")
+		return false
+	}
+	return true
+}
+
+func parseLimitQuery(r *http.Request, def, max int) int {
+	if v := r.URL.Query().Get("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			return n
+		}
+	}
+	return def
+}
+
+func (s *Server) handlePostgresOverview(w http.ResponseWriter, r *http.Request) {
+	a, ok := authFromContext(r.Context())
+	if !ok || !s.requireAtLeast(w, a, "viewer") || !s.requirePostgres(w) {
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+	defer cancel()
+	out, err := s.pgMonitor.Overview(ctx)
+	if err != nil {
+		writeInternalError(w, "postgres_overview", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, out)
+}
+
+func (s *Server) handlePostgresQueries(w http.ResponseWriter, r *http.Request) {
+	a, ok := authFromContext(r.Context())
+	if !ok || !s.requireAtLeast(w, a, "viewer") || !s.requirePostgres(w) {
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+	defer cancel()
+	out, err := s.pgMonitor.TopQueries(ctx, parseLimitQuery(r, 20, 100))
+	if err != nil {
+		writeInternalError(w, "postgres_queries", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, out)
+}
+
+func (s *Server) handlePostgresLocks(w http.ResponseWriter, r *http.Request) {
+	a, ok := authFromContext(r.Context())
+	if !ok || !s.requireAtLeast(w, a, "viewer") || !s.requirePostgres(w) {
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+	defer cancel()
+	out, err := s.pgMonitor.Locks(ctx)
+	if err != nil {
+		writeInternalError(w, "postgres_locks", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"items": out})
+}
+
+func (s *Server) handlePostgresTables(w http.ResponseWriter, r *http.Request) {
+	a, ok := authFromContext(r.Context())
+	if !ok || !s.requireAtLeast(w, a, "viewer") || !s.requirePostgres(w) {
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+	defer cancel()
+	out, err := s.pgMonitor.Tables(ctx, parseLimitQuery(r, 20, 100))
+	if err != nil {
+		writeInternalError(w, "postgres_tables", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"items": out})
+}
+
+func (s *Server) handlePostgresRecommendations(w http.ResponseWriter, r *http.Request) {
+	a, ok := authFromContext(r.Context())
+	if !ok || !s.requireAtLeast(w, a, "viewer") || !s.requirePostgres(w) {
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
+	defer cancel()
+	out, err := s.pgMonitor.Recommendations(ctx)
+	if err != nil {
+		writeInternalError(w, "postgres_recommendations", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, out)
+}
+
+func (s *Server) handleMonitoringCorrelation(w http.ResponseWriter, r *http.Request) {
+	a, ok := authFromContext(r.Context())
+	if !ok || !s.requireAtLeast(w, a, "viewer") || !s.requirePostgres(w) {
+		return
+	}
+	window := 60
+	if v := r.URL.Query().Get("window"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			window = n
+		}
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
+	defer cancel()
+	out, err := s.pgMonitor.Correlation(ctx, window)
+	if err != nil {
+		writeInternalError(w, "monitoring_correlation", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, out)
+}