Merge pull request #4915 from heyitsanthony/hash-barrier

etcdserver: force backend commit before acking physical compaction

etcdserver/v3demo_server.go

@@ -98,6 +98,12 @@ func (s *EtcdServer) Compact(ctx context.Context, r *pb.CompactionRequest) (*pb.
 	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Compaction: r})
 	if r.Physical && result.physc != nil {
 		<-result.physc
+		// The compaction is done deleting keys; the hash is now settled
+		// but the data is not necessarily committed. If there's a crash,
+		// the hash may revert to a hash prior to compaction completing
+		// if the compaction resumes. Force the finished compaction to
+		// commit so it won't resume following a crash.
+		s.be.ForceCommit()
 	}
 	if err != nil {
 		return nil, err

storage/kvstore.go

@@ -357,16 +357,21 @@ func (s *store) restore() error {
 	}
 
 	_, scheduledCompactBytes := tx.UnsafeRange(metaBucketName, scheduledCompactKeyName, nil, 0)
+	scheduledCompact := int64(0)
 	if len(scheduledCompactBytes) != 0 {
-		scheduledCompact := bytesToRev(scheduledCompactBytes[0]).main
-		if scheduledCompact > s.compactMainRev {
-			log.Printf("storage: resume scheduled compaction at %d", scheduledCompact)
-			go s.Compact(scheduledCompact)
+		scheduledCompact = bytesToRev(scheduledCompactBytes[0]).main
+		if scheduledCompact <= s.compactMainRev {
+			scheduledCompact = 0
 		}
 	}
 
 	tx.Unlock()
 
+	if scheduledCompact != 0 {
+		s.Compact(scheduledCompact)
+		log.Printf("storage: resume scheduled compaction at %d", scheduledCompact)
+	}
+
 	return nil
 }