Twisted Klein:同步行为

时间:2016-07-19 19:07:05

标签: python asynchronous twisted synchronous klein-mvc

我正在使用Twisted Klein,因为该框架的一个承诺是Asynchronous,但我测试了我开发的app和一些用于测试的代码,框架行为似乎是同步的。

测试服务器代码是:

# -*- encoding: utf-8 -*-
import json
import time
from datetime import datetime

from klein import Klein

app = Klein()

def setHeader(request, content_type):

    request.setHeader('Access-Control-Allow-Origin', '*')
    request.setHeader('Access-Control-Allow-Methods', 'GET')
    request.setHeader('Access-Control-Allow-Headers', 'x-prototype-version,x-requested-with')
    request.setHeader('Access-Control-Max-Age', 2520)
    request.setHeader('Content-type', content_type)


def cleanParams(params):

    for key in params.keys():

        param = params[key]
        params[key] = param[0]

    return params


@app.route('/test/', methods=["GET"])
def test(request):

    setHeader(request,'application/json')

    time.sleep(5)

    return json.dumps([str(datetime.now())])

if __name__ == "__main__":
    app.run(host='0.0.0.0',port=12030)

测试请求是:

# -*- encoding: utf-8 -*-
import requests
from datetime import datetime

if __name__ == "__main__":

    url = "http://192.168.50.205:12030"

    params = {
    }

    print datetime.now()
    for i in xrange(6):
        result = requests.get(url + "/test/", params)

        print datetime.now(), result.json()

启动服务器,如果我单独运行第二个代码:

2016-07-19 12:50:53.530000
2016-07-19 12:50:58.570000 [u'2016-07-19 12:50:58.548000']
2016-07-19 12:51:03.604000 [u'2016-07-19 12:51:03.589000']
2016-07-19 12:51:08.634000 [u'2016-07-19 12:51:08.625000']
2016-07-19 12:51:13.670000 [u'2016-07-19 12:51:13.654000']
2016-07-19 12:51:18.717000 [u'2016-07-19 12:51:18.708000']
2016-07-19 12:51:23.764000 [u'2016-07-19 12:51:23.748000']

完美,但如果我同时运行两个实例:

实例1:

2016-07-19 12:53:05.025000
2016-07-19 12:53:10.057000 [u'2016-07-19 12:53:10.042000']
2016-07-19 12:53:20.113000 [u'2016-07-19 12:53:20.097000']
2016-07-19 12:53:30.181000 [u'2016-07-19 12:53:30.166000']
2016-07-19 12:53:40.236000 [u'2016-07-19 12:53:40.219000']
2016-07-19 12:53:50.316000 [u'2016-07-19 12:53:50.294000']
2016-07-19 12:54:00.381000 [u'2016-07-19 12:54:00.366000']

实例2:

2016-07-19 12:53:05.282000
2016-07-19 12:53:15.074000 [u'2016-07-19 12:53:15.059000']
2016-07-19 12:53:25.141000 [u'2016-07-19 12:53:25.125000']
2016-07-19 12:53:35.214000 [u'2016-07-19 12:53:35.210000']
2016-07-19 12:53:45.270000 [u'2016-07-19 12:53:45.255000']
2016-07-19 12:53:55.362000 [u'2016-07-19 12:53:55.346000']
2016-07-19 12:54:05.402000 [u'2016-07-19 12:54:05.387000']

服务器输出:

2016-07-19 12:53:10-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:04 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:15-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:10 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:20-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:15 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:25-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:20 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:30-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:25 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:35-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:30 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:40-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:35 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:45-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:40 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:50-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:45 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:53:55-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:50 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:54:00-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:53:55 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"
2016-07-19 12:54:05-0400 [-] "192.168.50.205" - - [19/Jul/2016:16:54:00 +0000] "GET /test/ HTTP/1.1" 200 30 "-" "python-requests/2.9.1"

正如您所看到的,服务器阻止当前执行,它似乎在同步而非异步。

我缺少什么?

最诚挚的问候。

1 个答案:

答案 0 :(得分:4)

你错过了Twisted的许多重要概念。关于同步行为,你绝对正确,如果你没有明确地使用异步函数(即Deferreds),Klein就像Flask或Bottle一样表现同步框架。在您的示例中,您没有使用任何异步功能,因此您可以按顺序执行代码。查看https://github.com/notoriousno/klein-basics/blob/intro/nonblocking.rst这可以帮助您了解Klein和Twisted中异步的基础知识。提醒读者延迟不要让你的代码神奇地异步!你必须仔细设计以实现并发执行。

使代码异步

让我们尝试修复您的代码,使其以异步方式运行。我将逐节介绍这些概念。如果需要更多信息,请发表评论,我将解决它。让我们从所需的导入开始:

from klein import Klein
from twisted.internet import defer, reactor

的setHeader()

接下来让我们来看看setHeader()功能。 request.setHeader功能相当快,因此可以多次运行而不会出现严重阻塞。因此,可以使用生成Deferred对象的函数,该对象具有将设置各种标题键/值对的回调:

def setHeader(request, content_type):

    def _setHeader(previous_result, header, value):
        request.setHeader(header, value)

    d = defer.Deferred()
    d.addCallback(_setHeader, 'Access-Control-Allow-Origin', '*')
    d.addCallback(_setHeader, 'Access-Control-Allow-Methods', 'GET')
    d.addCallback(_setHeader, 'Access-Control-Allow-Headers', 'x-prototype-version,x-requested-with')
    d.addCallback(_setHeader, 'Access-Control-Max-Age', '2520')
    d.addCallback(_setHeader, 'Content-type', content_type)
    return d

我们没有详细介绍,我们正在使用Deferred.addCallback()将回调链接在一起。在这种情况下,回调函数是本地_setHeader(),它只是设置标题。最后,该函数将返回Deferred。如果您注意到,_setHeader()接受了previous_result参数,请暂时忽略它们。

cleanParams()

如果正在使用循环(forwhile),通常最好使用inlineCallbacksyield结果。使用此方法可以在不阻塞主ioloop的情况下以同步方式运行。

@defer.inlineCallbacks
def cleanParams(params):
    for key in sorted(params):
        param = params[key]
        params[key] = yield param[0]

    defer.returnValue(str(params))    # if py3 then use ``return params``

这是一个很糟糕的例子,但它应该说明如何使用yield来等待一个值。另外,setHeader()函数也可以使用inlineCallbacksyields。我想演示多个异步样式。

Klein Routes

最后,让我们实际使用路由中的异步函数:

app = Klein()

@app.route('/test/', methods=["GET"])
def test(request):
    asyncClean = cleanParams(request.args)
    asyncClean.addCallback(request.write)

    asyncSetHeader = setHeader(request,'application/json')
    reactor.callLater(5, asyncSetHeader.callback, None)

    def render(results, req):
        req.write(json.dumps([str(datetime.now())]))

    finalResults = defer.gatherResults([asyncClean, asyncSetHeader])
    finalResults.addCallback(render, request)
    return finalResults

不要忘记!首先我们致电cleanParams(),然后返回Deferred,当它完成时,returnValue将被写入反应机构。接下来,标题将通过setHeader()设置,显式返回Deferred。你使用的是time.sleep(5)而你无意中阻塞了整个反应堆循环。在Klein / Twisted中,如果您想在以后做某事,通常会使用callLater()。最后,我们通过asyncClean等待延迟asyncSetHeadergatherResults()的结果,并将时间戳写入响应正文。

最终守则

server.py

import json
from datetime import datetime

from klein import Klein
from twisted.internet import defer, reactor


app = Klein()

def setHeader(request, content_type):

    def _setHeader(previous_result, header, value):
        request.setHeader(header, value)

    d = defer.Deferred()
    d.addCallback(_setHeader, 'Access-Control-Allow-Origin', '*')
    d.addCallback(_setHeader, 'Access-Control-Allow-Methods', 'GET')
    d.addCallback(_setHeader, 'Access-Control-Allow-Headers', 'x-prototype-version,x-requested-with')
    d.addCallback(_setHeader, 'Access-Control-Max-Age', '2520')
    d.addCallback(_setHeader, 'Content-type', content_type)
    return d


@defer.inlineCallbacks
def cleanParams(params):
    for key in sorted(params):
        param = params[key]
        params[key] = yield param[0]

    defer.returnValue(str(params))


@app.route('/test/', methods=["GET"])
def test(request):
    asyncClean = cleanParams(request.args)
    asyncClean.addCallback(request.write)       # write the result from cleanParams() to the response

    asyncSetHeader = setHeader(request,'application/json')
    reactor.callLater(5, asyncSetHeader.callback, None)

    def render(results, req):
        req.write(json.dumps([str(datetime.now())]))

    finalResults = defer.gatherResults([asyncClean, asyncSetHeader])
    finalResults.addCallback(render, request)
    return finalResults

if __name__ == "__main__":
    app.run(host='0.0.0.0',port=12030)

test.sh

curl -v -X GET http://localhost:12030/test/?hello=world\&foo=bar\&fizz=buzz