code: protected void sendAppendRequest(Connection connection, MemberState member, AppendRequest request) {
      long timestamp = System.nanoTime();
  
      logger.trace("{} - Sending {} to {}", context.getCluster().member().address(), request, member.getMember().address());
      connection.<AppendRequest, AppendResponse>sendAndReceive(request).whenComplete((response, error) -> {
        context.checkThread();
  
        // Complete the append to the member.
        if (!request.entries().isEmpty()) {
          member.completeAppend(System.nanoTime() - timestamp);
        } else {
          member.completeAppend();
        }
  
        if (open) {
          if (error == null) {
            logger.trace("{} - Received {} from {}", context.getCluster().member().address(), response, member.getMember().address());
            handleAppendResponse(member, request, response);
          } else {
            handleAppendResponseFailure(member, request, error);
          }
        }
      });
  
      updateNextIndex(member, request);
      if (!request.entries().isEmpty() && hasMoreEntries(member)) {
        appendEntries(member);
      }
    }
docs: Sends a commit message.