Add verification to verify there is no duplicated keys in the bucket …

…buffer

Signed-off-by: Benjamin Wang <benjamin.ahrtr@gmail.com>

server/storage/backend/tx_buffer.go

@@ -16,6 +16,7 @@ package backend
 
 import (
 	"bytes"
+	"fmt"
 	"sort"
 
 	"go.etcd.io/etcd/client/pkg/v3/verify"
@@ -81,6 +82,7 @@ func (txw *txWriteBuffer) writeback(txr *txReadBuffer) {
 	for k, wb := range txw.buckets {
 		rb, ok := txr.buckets[k]
 		if !ok {
+			verifyNoDuplicatedKeys(wb)
 			delete(txw.buckets, k)
 			txr.buckets[k] = wb
 			continue
@@ -206,15 +208,19 @@ func (bb *bucketBuffer) merge(bbsrc *bucketBuffer) {
 
 	sort.Stable(bb)
 
-	// remove duplicates, using only newest update
-	widx := 0
-	for ridx := 1; ridx < bb.used; ridx++ {
-		if !bytes.Equal(bb.buf[ridx].key, bb.buf[widx].key) {
-			widx++
+	verifyNoDuplicatedKeys(bb)
+}
+
+func verifyNoDuplicatedKeys(bb *bucketBuffer) {
+	verify.Verify(func() {
+		keyMaps := make(map[string]struct{})
+		for _, kv := range bb.buf {
+			if _, ok := keyMaps[string(kv.key)]; ok {
+				panic(fmt.Sprintf("found duplicated keys in the bucketBuffer: %s", string(kv.key)))
+			}
+			keyMaps[string(kv.key)] = struct{}{}
 		}
-		bb.buf[widx] = bb.buf[ridx]
-	}
-	bb.used = widx + 1
+	})
 }
 
 func (bb *bucketBuffer) Len() int { return bb.used }