机械化+异步浏览器调用

Question

我正在寻找一种解决方案，可以在不等待答复的情况下发出大量异步 Web 请求。

这是我当前的代码：

import mechanize
from mechanize._opener import urlopen
from mechanize._form import ParseResponse
from multiprocessing import Pool

brow = mechanize.Browser()
brow.open('https://website.com')

#Login
brow.select_form(nr = 0)

brow.form['username'] = 'user'
brow.form['password'] = 'password'
brow.submit()

while(true):
    #async open the browser until some state is fullfilled
    brow.open('https://website.com/needthiswebsite')

上面代码的问题是，如果我尝试打开两个浏览器，bro2 必须等待 bro1 完成才能启动。 （它的阻塞）

bro1.open('https://website.com/needthiswebsite')
bro2.open('https://website.com/needthiswebsite')

解决方案的尝试：

#PSUDO-CODE

#GLOBAL VARIABLE STATE
boolean state = true

while(state):
    #async open the browser until some state is full filled
    #I spam this function until I get a positive answer from one of the calls
    pool = Pool(processes = 1)
    result = pool.apply_async(openWebsite,[brow1],callback = updateState)

def openWebsite(browser):
   result = browser.open('https://website.com/needthiswebsite')
   if result.something() == WHATIWANT:
        return true
   return false

def updateState(state):
    state = true

我试图为我的问题实施类似的解决方案，例如： Asynchronous method call in Python?stackoverflow 上的问题。

问题是我在尝试使用 pool.apply_async(brow.open()) 时遇到错误

错误信息：

PicklingError: Can't pickle : attribute lookup builtin.function failed

我尝试了很多方法来修复 PicklingError，但似乎没有任何效果。

• 是否可以通过 mechanize 做到这一点？
• 我应该改用另一个库，比如 urllib2 或类似的东西吗？

任何帮助将不胜感激:)

Answer 1

mechanize.Browser 对象不可腌制，因此不能传递给 pool.apply_async（或任何其他需要将对象发送到子进程的方法）：

>>> b = mechanize.Browser()
>>> import pickle
>>> pickle.dumps(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/pickle.py", line 1374, in dumps
    Pickler(file, protocol).dump(obj)
  File "/usr/lib/python2.7/pickle.py", line 224, in dump
    self.save(obj)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 725, in save_inst
    save(stuff)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 663, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 600, in save_list
    self._batch_appends(iter(obj))
  File "/usr/lib/python2.7/pickle.py", line 615, in _batch_appends
    save(x)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 725, in save_inst
    save(stuff)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 663, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 306, in save
    rv = reduce(self.proto)
  File "/usr/lib/python2.7/copy_reg.py", line 70, in _reduce_ex
    raise TypeError, "can't pickle %s objects" % base.__name__
TypeError: can't pickle instancemethod objects

最简单的做法是在每个子进程中创建Browser 实例，而不是在父进程中：

def openWebsite(url):
    brow = mechanize.Browser()
    brow.open('https://website.com')

    #Login
    brow.select_form(nr=0)

    brow.form['username'] = 'user'
    brow.form['password'] = 'password'
    brow.submit()

    result = brow.open(url)
    if result.something() == WHATIWANT:
         return True
    return False

理想情况下，您只需在父进程中使用Browser 对象登录，然后跨多个进程发出并行请求，但要使对象可腌制（如果可能的话）- 即使您设法删除了导致当前错误的 instancemethod 对象，除此之外，Browser 内可能还有更多不可腌制的对象。