[RATIS-1902] The snapshot index is set incorrectly in InstallSnapshotReplyProto

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: server
• Assignee: Tsz-wo Sze
• Reporter: Tsz-wo Sze
• Created: 12/Oct/23 15:52
• Updated: 25/Oct/23 01:50
• Resolved: 13/Oct/23 02:24

Description

// ServerProtoUtils.java
  static InstallSnapshotReplyProto toInstallSnapshotReplyProto(
      RaftPeerId requestorId, RaftGroupMemberId replyId,
      long currentTerm, InstallSnapshotResult result, long installedSnapshotIndex) {
    final RaftRpcReplyProto.Builder rb = toRaftRpcReplyProtoBuilder(requestorId,
        replyId, isSuccess(result));
    final InstallSnapshotReplyProto.Builder builder = InstallSnapshotReplyProto
        .newBuilder().setServerReply(rb).setTerm(currentTerm).setResult(result);
    if (installedSnapshotIndex > 0) {
      builder.setSnapshotIndex(installedSnapshotIndex);
    }
    return builder.build();
  }

In the code above, the condition installedSnapshotIndex > 0 above is invalid since it cannot be set to RaftLog.INVALID_LOG_INDEX (== -1). When the log is empty and there is no snapshots, it is correct for a follower replying RaftLog.INVALID_LOG_INDEX.

Issue Links

• causes: RATIS-1920 NPE in AppendLogResponseHandler
• relates to: RATIS-1883 Next Index should be always larger than Match Index in GrpcLogAppender
• links to: GitHub Pull Request #933