kvserver: use LogEngine to store fatal file

This decision is somewhat arbitrary, but seems logical to use the
LogEngine as the source of truth for now. For the fatal file, it could
also be either place, and both being checked on startup.

A reason to switch to the other engin might be that we decide to use the
FS directly only in one of the two engines, and then that would be
StateEngine because we already use it for the sideloaded log entry
files. But we aren't making this decision at this point.

Epic: none
Release note: none

Author: pav-kv

pkg/kv/kvserver/replica_consistency.go

@@ -679,7 +679,7 @@ func (r *Replica) computeChecksumPostApply(
 
 	// Caller is holding raftMu, so an engine snapshot is automatically
 	// Raft-consistent (i.e. not in the middle of an AddSSTable).
-	snap := r.store.TODOEngine().NewSnapshot(rditer.MakeReplicatedKeySpans(&desc)...)
+	snap := r.store.StateEngine().NewSnapshot(rditer.MakeReplicatedKeySpans(&desc)...)
 	if util.RaceEnabled {
 		ss := rditer.MakeReplicatedKeySpanSet(&desc)
 		defer ss.Release()
@@ -767,8 +767,12 @@ func (r *Replica) computeChecksumPostApply(
 		// early, the reply won't make it back to the leaseholder, so it will not be
 		// certain of completing the check. Since we're already in a goroutine
 		// that's about to end, just sleep for a few seconds and then terminate.
-		auxDir := r.store.TODOEngine().GetAuxiliaryDir()
-		_ = r.store.TODOEngine().Env().MkdirAll(auxDir, os.ModePerm)
+		//
+		// TODO(sep-raft-log): the decision to store the fatal file in LogEngine is
+		// somewhat arbitrary, make sure it's fine.
+		eng := r.store.LogEngine()
+		auxDir := eng.GetAuxiliaryDir()
+		_ = eng.Env().MkdirAll(auxDir, os.ModePerm)
 		path := base.PreventedStartupFile(auxDir)
 
 		const attentionFmt = `ATTENTION:
@@ -811,7 +815,7 @@ creation. These directories should be deleted, or inspected with caution.
 `
 		attentionArgs := []any{r, desc.Replicas(), redact.Safe(auxDir), redact.Safe(path)}
 		preventStartupMsg := fmt.Sprintf(attentionFmt, attentionArgs...)
-		if err := fs.WriteFile(r.store.TODOEngine().Env(), path, []byte(preventStartupMsg), fs.UnspecifiedWriteCategory); err != nil {
+		if err := fs.WriteFile(eng.Env(), path, []byte(preventStartupMsg), fs.UnspecifiedWriteCategory); err != nil {
 			log.KvExec.Warningf(ctx, "%v", err)
 		}
 

pkg/kv/kvserver/replica_corruption.go

@@ -45,8 +45,11 @@ func (r *Replica) setCorruptRaftMuLocked(
 	cErr.Processed = true
 	r.shMu.destroyStatus.Set(cErr, destroyReasonRemoved)
 
-	auxDir := r.store.TODOEngine().GetAuxiliaryDir()
-	_ = r.store.TODOEngine().Env().MkdirAll(auxDir, os.ModePerm)
+	// TODO(sep-raft-log): same as in replica_consistency.go, make sure storing
+	// files into the LogEngine is canonical.
+	eng := r.store.LogEngine()
+	auxDir := eng.GetAuxiliaryDir()
+	_ = eng.Env().MkdirAll(auxDir, os.ModePerm)
 	path := base.PreventedStartupFile(auxDir)
 
 	preventStartupMsg := fmt.Sprintf(`ATTENTION:
@@ -59,7 +62,7 @@ A file preventing this node from restarting was placed at:
 %s
 `, r, path)
 
-	if err := fs.WriteFile(r.store.TODOEngine().Env(), path, []byte(preventStartupMsg), fs.UnspecifiedWriteCategory); err != nil {
+	if err := fs.WriteFile(eng.Env(), path, []byte(preventStartupMsg), fs.UnspecifiedWriteCategory); err != nil {
 		log.KvExec.Warningf(ctx, "%v", err)
 	}