Question

我在我的一个Thrift函数定义中使用oneway修饰符：

...
oneway void secret_function(1: string x, 2: string y),
...

通过Thrift生成相应的Erlang代码时，将其转换为：

...
function_info('secret_function', reply_type) ->
  oneway_void;
function_info('secret_function', exceptions) ->
  {struct, []};
...

请注意那里的oneway_void原子。

执行secret_function函数时，出现以下错误：

=ERROR REPORT==== 2-Sep-2010::18:17:08 ===
oneway void secret_function threw error which must be ignored: {error,
                                                             function_clause,
                                                             [{thrift_protocol,
                                                               term_to_typeid,
                                                               [oneway_void]},
                                                              {thrift_protocol,
                                                               struct_write_loop,
                                                               3},
                                                              {thrift_protocol,
                                                               write,2},
                                                              {thrift_processor,
                                                               send_reply,
                                                               4},
                                                              {thrift_processor,
                                                               handle_function,
                                                               2},
                                                              {thrift_processor,
                                                               loop,1}]}

独立于用户代码中包含的可能错误，这里使用thrift_protocol:term_to_typeid/1原子作为参数调用oneway_void函数，这会导致函数子句。实际上，从代码中读取（thrift_protocol.erl）：

...
term_to_typeid(void) -> ?tType_VOID;
term_to_typeid(bool) -> ?tType_BOOL;
term_to_typeid(byte) -> ?tType_BYTE;
term_to_typeid(double) -> ?tType_DOUBLE;
term_to_typeid(i16) -> ?tType_I16;
term_to_typeid(i32) -> ?tType_I32;
term_to_typeid(i64) -> ?tType_I64;
term_to_typeid(string) -> ?tType_STRING;
term_to_typeid({struct, _}) -> ?tType_STRUCT;
term_to_typeid({map, _, _}) -> ?tType_MAP;
term_to_typeid({set, _}) -> ?tType_SET;
term_to_typeid({list, _}) -> ?tType_LIST.
...

一个错误？还有其他解释吗？为什么oneway_void被传递给该函数？

Answer 1

我想我知道幕后发生了什么。

我的Erlang代码（secret_function/2）正在返回{ok，pid（）}而不是简单的确定。即使这在概念上是错误的，因为我宣布了函数oneway_void，我花了一段时间来确定问题的原因。也许我们可以调整Thrift中的handle_succes函数，使其行为与h andle_function_catch已经完成的行为相同。这就是handle_function_catch目前的样子：

...
case {ErrType, ErrData} of
    _ when IsOneway ->
        Stack = erlang:get_stacktrace(),
        error_logger:warning_msg(
          "oneway void ~p threw error which must be ignored: ~p",
          [Function, {ErrType, ErrData, Stack}]),
        {State, ok};
...

即使该函数声明为oneway_void，当引发异常时，也会报告该问题。根据相同的推理，潜在的新handle_success函数可能如下所示：

handle_success(State = #thrift_processor{service = Service},
               Function,
               Result) ->
    ReplyType  = Service:function_info(Function, reply_type),
    StructName = atom_to_list(Function) ++ "_result",

    case Result of
        {reply, ReplyData} when ReplyType =:= oneway_void ->
            Stack = erlang:get_stacktrace(),
            error_logger:warning_msg(
              "oneway void ~p sent reply which must be ignored: ~p",
              [Function, {ReplyData, Stack}]),
            {State, ok};
                {reply, ReplyData} ->
            Reply = {{struct, [{0, ReplyType}]}, {StructName, ReplyData}},
            send_reply(State, Function, ?tMessageType_REPLY, Reply);

        ok when ReplyType == {struct, []} ->
            send_reply(State, Function, ?tMessageType_REPLY, {ReplyType, {StructName}});

        ok when ReplyType == oneway_void ->
            %% no reply for oneway void
            {State, ok}
    end.

这里我只是检查函数是否定义为oneway_void并且如果这是真的并且我仍然收到不同于原子ok的返回值，我报告事故，仍然忽略返回值。

这是开发人员使用更新的handle_success函数看到的内容：

=ERROR REPORT==== 7-Sep-2010::11:06:43 ===
oneway void secret_function sent reply which must be ignored: {{ok,
                                                                  <0.262.0>},
                                                                 []}

这可以挽救你的生命至少一次（cit。）。

在Thrift函数定义中使用“oneway void”

1 个答案: