Treat fee stats as a migration

cmd/soroban-rpc/internal/daemon/daemon.go

@@ -361,10 +361,12 @@ func (d *Daemon) mustInitializeStorage(cfg *config.Config) *feewindow.FeeWindows
 	//    means the final range is only the fee stat analysis range.
 	//
 	feeStatsRange, err := db.GetMigrationLedgerRange(readTxMetaCtx, d.db, maxFeeRetentionWindow)
+	dataMigrations.Append(feeWindows.AsMigration(feeStatsRange))
 	if err != nil {
 		d.logger.WithError(err).Fatal("could not get ledger range for fee stats")
 	}
-	ledgerSeqRange := dataMigrations.ApplicableRange().Merge(feeStatsRange)
+
+	ledgerSeqRange := dataMigrations.ApplicableRange()
 
 	//
 	// 5. Apply migration for events & transactions, and perform fee stat analysis.
@@ -389,12 +391,6 @@ func (d *Daemon) mustInitializeStorage(cfg *config.Config) *feewindow.FeeWindows
 					Debug("Still initializing in-memory store")
 			}
 
-			if feeStatsRange.IsLedgerIncluded(currentSeq) { // skip irrelevant ledgers
-				if err = feeWindows.IngestFees(txMeta); err != nil {
-					d.logger.WithError(err).Fatal("could not initialize fee stats")
-				}
-			}
-
 			if err := dataMigrations.Apply(readTxMetaCtx, txMeta); err != nil {
 				d.logger.WithError(err).Fatal("could not apply migration for ledger ", currentSeq)
 			}

cmd/soroban-rpc/internal/feewindow/feewindow.go

@@ -2,6 +2,7 @@
 package feewindow
 
 import (
+	"context"
 	"errors"
 	"io"
 	"slices"
@@ -194,3 +195,34 @@ func (fw *FeeWindows) IngestFees(meta xdr.LedgerCloseMeta) error {
 	}
 	return nil
 }
+
+func (fw *FeeWindows) AsMigration(seqRange db.LedgerSeqRange) db.Migration {
+	return &feeWindowMigration{
+		firstLedger: seqRange.First,
+		lastLedger:  seqRange.Last,
+		windows:     fw,
+	}
+}
+
+type feeWindowMigration struct {
+	firstLedger uint32
+	lastLedger  uint32
+	windows     *FeeWindows
+}
+
+func (fw *feeWindowMigration) ApplicableRange() db.LedgerSeqRange {
+	return db.LedgerSeqRange{
+		First: fw.firstLedger,
+		Last:  fw.lastLedger,
+	}
+}
+
+func (fw *feeWindowMigration) Apply(_ context.Context, meta xdr.LedgerCloseMeta) error {
+	return fw.windows.IngestFees(meta)
+}
+
+func (fw *feeWindowMigration) Commit(_ context.Context) error {
+	return nil // no-op
+}
+
+var _ db.Migration = &feeWindowMigration{}