raft: Rename ErrSnapshotRequired To ErrCompacted.

raft/log.go

@@ -191,7 +191,7 @@ func (l *raftLog) lastTerm() uint64 {
 func (l *raftLog) term(i uint64) uint64 {
 	if i < l.unstable {
 		t, err := l.storage.Term(i)
-		if err == ErrSnapshotRequired {
+		if err == ErrCompacted {
 			return 0
 		} else if err != nil {
 			panic(err) // TODO(bdarnell)
@@ -299,7 +299,7 @@ func (l *raftLog) slice(lo uint64, hi uint64) []pb.Entry {
 	var ents []pb.Entry
 	if lo < l.unstable {
 		storedEnts, err := l.storage.Entries(lo, min(hi, l.unstable))
-		if err == ErrSnapshotRequired {
+		if err == ErrCompacted {
 			return nil
 		} else if err != nil {
 			panic(err) // TODO(bdarnell)

raft/storage.go

@@ -23,9 +23,9 @@ import (
 	pb "github.com/coreos/etcd/raft/raftpb"
 )
 
-// ErrSnapshotRequired is returned by Storage.Entries when a requested
+// ErrCompacted is returned by Storage.Entries when a requested
 // index is unavailable because it predates the last snapshot.
-var ErrSnapshotRequired = errors.New("snapshot required; requested index is too old")
+var ErrCompacted = errors.New("requested index is unavailable due to compaction")
 
 // Storage is an interface that may be implemented by the application
 // to retrieve log entries from storage.
@@ -80,7 +80,7 @@ func (ms *MemoryStorage) Entries(lo, hi uint64) ([]pb.Entry, error) {
 	ms.Lock()
 	defer ms.Unlock()
 	if lo <= ms.offset {
-		return nil, ErrSnapshotRequired
+		return nil, ErrCompacted
 	}
 	return ms.ents[lo-ms.offset : hi-ms.offset], nil
 }
@@ -90,7 +90,7 @@ func (ms *MemoryStorage) Term(i uint64) (uint64, error) {
 	ms.Lock()
 	defer ms.Unlock()
 	if i < ms.offset || i > ms.offset+uint64(len(ms.ents)) {
-		return 0, ErrSnapshotRequired
+		return 0, ErrCompacted
 	}
 	return ms.ents[i-ms.offset].Term, nil
 }