avoid possible nil due to race condition

chrisluuber · chrisluuber · commit a0181682963a · 2021-04-07T20:55:52.000-07:00
fix https://github.com/chrislusf/seaweedfs/issues/1974
diff --git a/server.go b/server.go
@@ -1296,7 +1296,8 @@ func (s *server) saveSnapshot() error {
 	s.snapshot = s.pendingSnapshot
 
 	// Delete the previous snapshot if there is any change
-	if tmp != nil && !(tmp.LastIndex == s.snapshot.LastIndex && tmp.LastTerm == s.snapshot.LastTerm) {
+	currentSnapshot := s.snapshot
+	if tmp != nil && currentSnapshot != nil && !(tmp.LastIndex == currentSnapshot.LastIndex && tmp.LastTerm == currentSnapshot.LastTerm) {
 		tmp.remove()
 	}
 	s.pendingSnapshot = nil

Original file line number	Diff line number	Diff line change
`@@ -1296,7 +1296,8 @@ func (s *server) saveSnapshot() error {`
`1296`	`1296`	`s.snapshot = s.pendingSnapshot`
`1297`	`1297`
`1298`	`1298`	`// Delete the previous snapshot if there is any change`
`1299`		`- if tmp != nil && !(tmp.LastIndex == s.snapshot.LastIndex && tmp.LastTerm == s.snapshot.LastTerm) {`
	`1299`	`+ currentSnapshot := s.snapshot`
	`1300`	`+ if tmp != nil && currentSnapshot != nil && !(tmp.LastIndex == currentSnapshot.LastIndex && tmp.LastTerm == currentSnapshot.LastTerm) {`
`1300`	`1301`	`tmp.remove()`
`1301`	`1302`	`}`
`1302`	`1303`	`s.pendingSnapshot = nil`