improve scheduler

internal/report/snapshots.go

@@ -169,7 +169,11 @@ func MigrateSnapshotRegistry(ctx context.Context, database db.Database) (Snapsho
 		}
 		if snapshotTime.IsZero() {
 			suffix := strings.TrimPrefix(table, "inventory_hourly_")
-			if parsed, parseErr := time.Parse("2006010215", suffix); parseErr == nil {
+			if parsed, parseErr := time.Parse("200601021504", suffix); parseErr == nil {
+				// Name encoded with date+hour+minute (e.g., 15-minute cadence)
+				snapshotTime = parsed
+			} else if parsed, parseErr := time.Parse("2006010215", suffix); parseErr == nil {
+				// Legacy hour-only encoding
 				snapshotTime = parsed
 			} else if epoch, parseErr := strconv.ParseInt(suffix, 10, 64); parseErr == nil {
 				snapshotTime = time.Unix(epoch, 0)

main.go

@@ -184,10 +184,7 @@ func main() {
 	cronAggregateFrequency = durationFromSeconds(s.Values.Settings.VcenterInventoryAggregateSeconds, 86400)
 	logger.Debug("Setting VM inventory daily aggregation cronjob frequency to", "frequency", cronAggregateFrequency)
 
-	startsAt3 := time.Now().Add(cronSnapshotFrequency)
-	if cronSnapshotFrequency == time.Hour {
-		startsAt3 = time.Now().Truncate(time.Hour).Add(time.Hour)
-	}
+	startsAt3 := alignStart(time.Now(), cronSnapshotFrequency)
 	job3, err := c.NewJob(
 		gocron.DurationJob(cronSnapshotFrequency),
 		gocron.NewTask(func() {
@@ -296,6 +293,18 @@ func main() {
 	os.Exit(0)
 }
 
+// alignStart snaps the first run to a sensible boundary (hour or 15-minute block) when possible.
+func alignStart(now time.Time, freq time.Duration) time.Time {
+	if freq == time.Hour {
+		return now.Truncate(time.Hour).Add(time.Hour)
+	}
+	quarter := 15 * time.Minute
+	if freq%quarter == 0 {
+		return now.Truncate(quarter).Add(quarter)
+	}
+	return now.Add(freq)
+}
+
 func durationFromSeconds(value int, fallback int) time.Duration {
 	if value <= 0 {
 		return time.Second * time.Duration(fallback)