add comment for peer storage

Signed-off-by: linning <linningde25@gmail.com>

kv/raftstore/peer_storage.go

@@ -244,34 +244,10 @@ func (ps *PeerStorage) validateSnap(snap *eraftpb.Snapshot) bool {
 	return true
 }
 
-// Append the given entries to the raft log using previous last index or self.last_index.
+// Append the given entries to the raft log and update ps.raftState also delete log entries that will
-// Return the new last index for later update. After we commit in engine, we can set last_index
+// never be committed
-// to the return one.
 func (ps *PeerStorage) Append(entries []eraftpb.Entry, raftWB *engine_util.WriteBatch) error {
 	// Your Code Here (2B).
-	// TODO: Delete Start
-	log.Debugf("%s append %d entries", ps.Tag, len(entries))
-	prevLastIndex := ps.raftState.LastIndex
-	if len(entries) == 0 {
-		return nil
-	}
-	lastEntry := entries[len(entries)-1]
-	lastIndex := lastEntry.Index
-	lastTerm := lastEntry.Term
-	for _, entry := range entries {
-		err := raftWB.SetMeta(meta.RaftLogKey(ps.region.Id, entry.Index), &entry)
-		if err != nil {
-			return err
-		}
-	}
-	// Delete any previously appended log entries which never committed.
-	for i := lastIndex + 1; i <= prevLastIndex; i++ {
-		raftWB.DeleteMeta(meta.RaftLogKey(ps.region.Id, i))
-	}
-	ps.raftState.LastIndex = lastIndex
-	ps.raftState.LastTerm = lastTerm
-	return nil
-	// TODO: Delete End
 }
 
 func (ps *PeerStorage) clearMeta(kvWB, raftWB *engine_util.WriteBatch) error {
@@ -290,6 +266,7 @@ func (ps *PeerStorage) clearExtraData(newRegion *metapb.Region) {
 	}
 }
 
+// ClearMeta delete stale metadata like raftState, applyState, regionState and raft log entries
 func ClearMeta(engines *engine_util.Engines, kvWB, raftWB *engine_util.WriteBatch, regionID uint64, lastIndex uint64) error {
 	start := time.Now()
 	kvWB.DeleteMeta(meta.RegionStateKey(regionID))
@@ -327,102 +304,18 @@ func ClearMeta(engines *engine_util.Engines, kvWB, raftWB *engine_util.WriteBatc
 	return nil
 }
 
-// Apply the peer with given snapshot.
+// Apply the peer with given snapshot
 func (ps *PeerStorage) ApplySnapshot(snapshot *eraftpb.Snapshot, kvWB *engine_util.WriteBatch, raftWB *engine_util.WriteBatch) (*ApplySnapResult, error) {
+	// Hint: things need to do here including: update peer storage state like raftState and applyState, etc,
+	// and send RegionTaskApply task to region worker through ps.regionSched, also remenber call ps.clearMeta
+	// and ps.clearExtraData to delete stale data
 	// Your Code Here (2B).
-	// TODO: Delete Start
-	log.Infof("%v begin to apply snapshot", ps.Tag)
-
-	snapData := new(rspb.RaftSnapshotData)
-	if err := snapData.Unmarshal(snapshot.Data); err != nil {
-		return nil, err
-	}
-
-	if snapData.Region.Id != ps.region.Id {
-		return nil, fmt.Errorf("mismatch region id %v != %v", snapData.Region.Id, ps.region.Id)
-	}
-
-	if ps.isInitialized() {
-		// we can only delete the old data when the peer is initialized.
-		if err := ps.clearMeta(kvWB, raftWB); err != nil {
-			return nil, err
-		}
-		ps.clearExtraData(snapData.Region)
-	}
-
-	ps.raftState.LastIndex = snapshot.Metadata.Index
-	ps.raftState.LastTerm = snapshot.Metadata.Term
-
-	applyRes := &ApplySnapResult{
-		PrevRegion: ps.region,
-		Region:     snapData.Region,
-	}
-	ps.region = snapData.Region
-	ps.applyState = rspb.RaftApplyState{
-		AppliedIndex: snap.Metadata.Index,
-		// The snapshot only contains log which index > applied index, so
-		// here the truncate state's (index, term) is in snapshot metadata.
-		TruncatedState: &rspb.RaftTruncatedState{
-			Index: snapshot.Metadata.Index,
-			Term:  snapshot.Metadata.Term,
-		},
-	}
-	kvWB.SetMeta(meta.ApplyStateKey(ps.region.GetId()), &ps.applyState)
-	meta.WriteRegionState(kvWB, snapData.Region, rspb.PeerState_Normal)
-	ch := make(chan bool)
-	ps.snapState = snap.SnapState{
-		StateType: snap.SnapState_Applying,
-	}
-	ps.regionSched <- &runner.RegionTaskApply{
-		RegionId: ps.region.Id,
-		Notifier: ch,
-		SnapMeta: snapshot.Metadata,
-		StartKey: snapData.Region.GetStartKey(),
-		EndKey:   snapData.Region.GetEndKey(),
-	}
-	// wait until apply finish
-	<-ch
-
-	log.Debugf("%v apply snapshot for region %v with state %v ok", ps.Tag, snapData.Region, ps.applyState)
-	return applyRes, nil
-	// TODO: Delete End
 }
 
 /// Save memory states to disk.
 /// Do not modify ready in this function, this is a requirement to advance the ready object properly later.
 func (ps *PeerStorage) SaveReadyState(ready *raft.Ready) (*ApplySnapResult, error) {
 	// Your Code Here (2B).
-	// TODO: Delete Start
-	kvWB, raftWB := new(engine_util.WriteBatch), new(engine_util.WriteBatch)
-	prevRaftState := ps.raftState
-
-	var applyRes *ApplySnapResult = nil
-	var err error
-	if !raft.IsEmptySnap(&ready.Snapshot) {
-		applyRes, err = ps.ApplySnapshot(&ready.Snapshot, kvWB, raftWB)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	if len(ready.Entries) != 0 {
-		if err := ps.Append(ready.Entries, raftWB); err != nil {
-			return nil, err
-		}
-	}
-
-	if !raft.IsEmptyHardState(ready.HardState) {
-		ps.raftState.HardState = &ready.HardState
-	}
-
-	if !proto.Equal(&prevRaftState, &ps.raftState) {
-		raftWB.SetMeta(meta.RaftStateKey(ps.region.GetId()), &ps.raftState)
-	}
-
-	kvWB.MustWriteToDB(ps.Engines.Kv)
-	raftWB.MustWriteToDB(ps.Engines.Raft)
-	return applyRes, nil
-	// TODO: Delete End
 }
 
 func (ps *PeerStorage) ClearData() {