improve logging and concurrent vcenter inventory

internal/tasks/inventoryHelpers.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
+	"log/slog"
 	"strconv"
 	"strings"
 	"time"
@@ -44,7 +45,7 @@ func boolStringFromInterface(value interface{}) string {
 
 // latestHourlySnapshotBefore finds the most recent hourly snapshot table prior to the given time, skipping empty tables.
 func latestHourlySnapshotBefore(ctx context.Context, dbConn *sqlx.DB, cutoff time.Time) (string, error) {
-	tables, err := listLatestHourlyWithRows(ctx, dbConn, "", cutoff.Unix(), 1)
+	tables, err := listLatestHourlyWithRows(ctx, dbConn, "", cutoff.Unix(), 1, nil)
 	if err != nil {
 		return "", err
 	}
@@ -68,7 +69,7 @@ func parseSnapshotTime(table string) (int64, bool) {
 }
 
 // listLatestHourlyWithRows returns recent hourly snapshot tables (ordered desc by time) that have rows, optionally filtered by vcenter.
-func listLatestHourlyWithRows(ctx context.Context, dbConn *sqlx.DB, vcenter string, beforeUnix int64, limit int) ([]snapshotTable, error) {
+func listLatestHourlyWithRows(ctx context.Context, dbConn *sqlx.DB, vcenter string, beforeUnix int64, limit int, logger *slog.Logger) ([]snapshotTable, error) {
 	if limit <= 0 {
 		limit = 50
 	}
@@ -88,31 +89,54 @@ LIMIT ?
 	for rows.Next() {
 		var name string
 		var ts int64
-		var count int64
+		var count sql.NullInt64
 		if scanErr := rows.Scan(&name, &ts, &count); scanErr != nil {
 			continue
 		}
 		if err := db.ValidateTableName(name); err != nil {
 			continue
 		}
-		// Use snapshot_count first; fall back to row check (and vcenter filter) only when needed.
-		if count == 0 {
-			if has, _ := db.TableHasRows(ctx, dbConn, name); !has {
-				continue
+		if count.Valid && count.Int64 == 0 {
+			if logger != nil {
+				logger.Debug("skipping snapshot table with zero count", "table", name, "snapshot_time", ts)
+			}
+			continue
+		}
+		probed := false
+		hasRows := true
+		start := time.Now()
+		if !count.Valid {
+			probed = true
+			if ok, err := db.TableHasRows(ctx, dbConn, name); err == nil {
+				hasRows = ok
+			} else {
+				hasRows = false
+				if logger != nil {
+					logger.Debug("snapshot table probe failed", "table", name, "error", err)
+				}
 			}
 		}
-		if vcenter != "" {
+		if vcenter != "" && hasRows {
+			probed = true
 			vrows, qerr := querySnapshotRows(ctx, dbConn, name, []string{"VmId"}, `"Vcenter" = ? LIMIT 1`, vcenter)
-			if qerr != nil {
-				continue
-			}
-			hasVcenter := vrows.Next()
-			vrows.Close()
-			if !hasVcenter {
-				continue
+			if qerr == nil {
+				hasRows = vrows.Next()
+				vrows.Close()
+			} else {
+				hasRows = false
+				if logger != nil {
+					logger.Debug("snapshot vcenter filter probe failed", "table", name, "vcenter", vcenter, "error", qerr)
+				}
 			}
 		}
-		out = append(out, snapshotTable{Table: name, Time: ts})
+		elapsed := time.Since(start)
+		if logger != nil {
+			logger.Debug("evaluated snapshot table", "table", name, "snapshot_time", ts, "snapshot_count", count, "probed", probed, "has_rows", hasRows, "elapsed", elapsed)
+		}
+		if !hasRows {
+			continue
+		}
+		out = append(out, snapshotTable{Table: name, Time: ts, Count: count})
 	}
 	return out, nil
 }