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在节俭函数定义中使用“单向空”

thrift-protocol thrift erlang

Roberto Aloi · 技术社区 · 16 年前

我用的是 oneway

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

当通过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 oneway_void

当 secret_function 函数执行时,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}]}

独立于用户代码中可能包含的bug,这里 thrift_protocol:term_to_typeid/1 正在使用调用函数 单向无效

...
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.
...

单向无效 传递给那个函数?

1 回复 | 直到 16 年前

Roberto Aloi 16 年前

我想我知道幕后发生了什么。

我的Erlang代码 secret_function/2 )返回{ok,pid()}而不是简单的ok。 oneway_void ,我花了一段时间才找出问题的原因。也许我们可以调整一下 handle_succes 在节俭中起作用,使它的行为与h一样 andle_function_catch 这就是 handle_function_catch 目前看来:

...
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};
...

,当引发异常时,将报告问题。根据相同的推理,一个潜在的新handle\u 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 单向无效 如果这是真的,我仍然收到一个不同于原子的返回值 ok

这就是开发人员在更新后的 handle_success

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

这至少能救你一次命(同上)。