当使用特定于yaws_api的代码时，Yaws“进程已死”

Question

我有一个小的雅斯appmod测试：

-module(webservice).
-include("../include/yaws_api.hrl").
-compile(export_all).

http(parse_query,Arg) ->
    yaws_api:parse_query(Arg);

out(Arg) -> 
    {html, [http(parse_query,Arg)]}.

当运行yaws_api:parse_query函数时，我从yaws交互模式得到以下错误报告：

Yaws process died: {function_clause,
                   [{yaws_server,binary_size,
                        [0,{"i",undefined}],
                        [{file,"yaws_server.erl"},{line,3015}]},
                    {yaws_server,binary_size,2,
                        [{file,"yaws_server.erl"},{line,3018}]},
                    {yaws_server,binary_size,2,
                        [{file,"yaws_server.erl"},{line,3018}]},
                    {yaws_server,deflate_accumulated,4,
                        [{file,"yaws_server.erl"},{line,3712}]},
                    {yaws_server,deliver_accumulated,4,
                        [{file,"yaws_server.erl"},{line,3666}]},
                    {yaws_server,finish_up_dyn_file,2,
                        [{file,"yaws_server.erl"},{line,2745}]},
                    {yaws_server,aloop,4,
                        [{file,"yaws_server.erl"},{line,1175}]},
                    {yaws_server,acceptor0,2,
                        [{file,"yaws_server.erl"},{line,1016}]}]}

appmod在config中设置为：

<server localhost>
    port = 8080
    listen = 127.0.0.1
    #docroot = /usr/share/yaws
    docroot = /usr/lib/yaws/www
    appmods = </,webservice>
    # dir_listings = true
</server>

Answer 1

尽管您没有显示它，但是看起来您试图访问的URL有一个查询字符串，该字符串至少有一个名为i的变量，如下所示：

http://example.com/foo?i=10

对于该URL，yaws_api:parse_query/1将返回[{"i","10"}]，然后尝试使用{html, iolist()}结构将其作为HTML返回给Yaws。不幸的是，[{"i","10"}]不是iolist、字符串或二进制文件，所以Yaws失败了。

您可以通过使用yaws_api:f/2调用将[{"i","10"}]转换为字符串来解决此问题，如下所示：

out(Arg) ->
    {html, yaws_api:f("~p", [http(parse_query,Arg)])}.

或者使用标准的io_lib:format/2调用：

out(Arg) ->
    {html, io_lib:format("~p", [http(parse_query,Arg)])}.

yaws_api:f/2函数只是io_lib:format/2的包装器。