Question

这是我正在使用的Prolog HTTP服务器：

:- use_module(library(http/thread_httpd)).
:- use_module(library(http/http_dispatch)).
:- use_module(library(http/html_write)).
:- use_module(library(http/json)).
:- use_module(library(http/json_convert)).
:- use_module(library(http/http_json)).
:- use_module(library(http/http_log)).

:- http_handler(root(handle), handle_rpc, []).

:- set_setting(http:logfile, '/home/john/Desktop/log.txt').

http_json:json_type('application/json').

% sample prolog program
f1(1).
f1(2).
f1(4).
f1(5).
f2(3).
f2(4).
f2(6).

server(Port) :-
    http_server(http_dispatch, [port(Port)]).

handle_rpc(Request) :-
    http_read_json(Request, JSONIn),
    json_to_prolog(JSONIn, PrologIn),
    evaluate(PrologIn, PrologOut), % application body
    PrologOut = JSONOut,
    reply_json(JSONOut).

evaluate(PrologIn, PrologOut) :-
    PrologIn = json([args=Query, password=PW, method=MethodName]),
    MethodName = eval,
    PW = blah,
    atom_to_term(Query, Term, Bindings),
    Goal =.. [findall, Bindings, Term, IR],
    call(Goal),
    sort(IR, Result),
    Result = PrologOut,
    format(atom(StringResult), "~q", [Result]),
    PrologOut = json([result=StringResult]).

这是我正在进行RPC调用的Python客户端：

import urllib2
import json

url = "http://192.168.157.128:5001/handle"
json_dict = { 'args' : "f1(S)", 'method' : 'eval', 'password' : 'blah' }
jdata = json.dumps( json_dict )
headers = {}
headers['Content-Type'] = 'application/json'
print jdata
req = urllib2.Request(url, jdata, headers)
res = urllib2.urlopen(req)
for line in res:
    print json.loads(line)

请求失败，出现500错误。在我的httpd.log文件中，我得到的唯一消息是：

/*Tue Aug 21 17:42:41 2012*/ request(10, 1345585361.981, [peer(ip(192,168,157,1)),method(post),request_uri('/handle'),path('/handle'),http_version(1-1),content_length(55),host('192.168.157.128'),port(5001),content_type('application/json'),connection(close),user_agent('Python-urllib/2.6')]).
completed(10, 0.000829367999999997, 815, 500, error("goal unexpectedly failed: user:handle_rpc([protocol(http),peer(ip(192,168,157,1)),pool(client(httpd@5001,user:http_dispatch,<stream>(0xf9c2b0),<stream>(0xf9c410))),input(<stream>(0xf9c2b0)),method(post),request_uri(/handle),path(/handle),http_version(1-1),accept_encoding(identity),content_length(55),host(192.168.157.128),port(5001),content_type(application/json),connection(close),user_agent(Python-urllib/2.6)])")).

就是这样，只是“目标意外失败了”。不，目标失败了。我想知道为什么失败了。

为什么这个Prolog RPC调用不起作用，为什么日志不告诉我出了什么问题？

0 个答案: