我有一个使用 Twisted 编写的小型 Web 服务器。我想做的一件事是让它从另一个 Web 服务器返回一个结果作为加载页面的响应。也就是说，服务器 A（通过http://A.com/resource）对 render_GET() 的响应应该是服务器 B 上不同 URL 的内容（通过http://B.com/resource2）。服务器 B 返回的内容是动态的，所以我不能只缓存它。
现在，服务器 A 可以很好地渲染页面，它只是无法渲染这个远程资源。我已经尝试过使用 Agent()，但我似乎无法从 B 获得响应，更不用说将其转发给 A。我知道我必须在某个地方从 render_GET 以及稍后接收该write()请求finish()。这是在cbBody回调中完成的，它被调用但无法到达原始请求来填充它。
这是服务器 A 的资源处理程序的一段代码：
def render_GET(self,request):
# try with canned content just to test the whole thing
bmpServer = BMPServer(ServerBURL,
"xyzzy",
"plugh")
d= bmpServer.postNotification({"a":123},request)
print "Deferred", d
return NOT_DONE_YET
这是服务器 A 上的另一个代码：
theRequest = None
def cbRequest(response,args):
print "response called"
print response
print args
print 'Response version:', response.version
print 'Response code:', response.code
print 'Response phrase:', response.phrase
print 'Response headers:'
print pformat(list(response.headers.getAllRawHeaders()))
d = readBody(response)
d.addCallback(cbBody)
return d
def cbBody(body):
print "Response body:"
print body
theRequest.write(body)
theRequest.finish()
theRequest = None
def cbError(failure):
print type(failure.value), failure # catch error here
print failure.value.reasons[0].printTraceback()
class BMPServer(object):
def __init__(self,url,arg1,arg2):
self.url = url
self.arg1 = arg1
self.arg2 = arg2
def postNotification(self,message,request):
theRequest = request
bmpMessage = {'arg1':self.token,
'arg2':self.appID,
'message':message}
print "Sending request to %s"%self.url
print "Create agent"
agent = Agent(reactor)
print "create request deferred"
print "url = %s" % self.url
d = agent.request('POST', self.url,
Headers({'User-Agent': ['Twisted Web Client Example']}),
MessageProducer(bmpMessage))
print "adding callback"
d.addCallbacks(cbRequest,cbError)
print "returning deferred"
return d
当我将其作为独立代码运行时（react()例如在资源之外，使用），它可以正常工作。但是，当我尝试如上所示包含它时，它似乎永远不会收到数据。我已经运行了 WireShark，所以我可以看到响应正在从服务器 B 返回，但数据从未出现在cbRequest().
例如，这是我看到的输出：
Sending request to http://localhost:8888/postMGCMNotificationService
Create agent
create request deferred
url = http://serverB:8888/postService
Message producer: body = {"arg2": "plugh", "arg1": "xyzzy", "message": {"a": 1}}
adding callback
returning deferred
testAgent: returning deferred
<Deferred at 0x10b54d290>
Writing body now
response called
<twisted.web._newclient.Response object at 0x1080753d0>
Response version: ('HTTP', 1, 1)
Response code: 200
Response phrase: OK
Response headers:
Response body:
{"result": false}
^CUnhandled error in Deferred:
Unhandled Error
Traceback (most recent call last):
File "/Library/Python/2.7/site-packages/Twisted-13.1.0_r39314-py2.7-macosx-10.8-intel.egg/twisted/web/_newclient.py", line 1151, in _bodyDataFinished_CONNECTED
self._bodyProtocol.connectionLost(reason)
File "/Library/Python/2.7/site-packages/Twisted-13.1.0_r39314-py2.7-macosx-10.8-intel.egg/twisted/web/client.py", line 1793, in connectionLost
self.deferred.callback(b''.join(self.dataBuffer))
File "/Library/Python/2.7/site-packages/Twisted-13.1.0_r39314-py2.7-macosx-10.8-intel.egg/twisted/internet/defer.py", line 382, in callback
self._startRunCallbacks(result)
File "/Library/Python/2.7/site-packages/Twisted-13.1.0_r39314-py2.7-macosx-10.8-intel.egg/twisted/internet/defer.py", line 490, in _startRunCallbacks
self._runCallbacks()
--- <exception caught here> ---
File "/Library/Python/2.7/site-packages/Twisted-13.1.0_r39314-py2.7-macosx-10.8-intel.egg/twisted/internet/defer.py", line 577, in _runCallbacks
current.result = callback(current.result, *args, **kw)
File "AServer.py", line 85, in cbBody
print theRequest
exceptions.UnboundLocalError: local variable 'theRequest' referenced before assignment
再看看这个，似乎如果我能想出一种方法来让这个请求结束，cbBody()一切都会很好。