如何防止 lxml.etree.HTML(data) 在特定数据类型上崩溃？

Question

我在运行 etree.HTML( data ) 处理很多不同的 data 内容。但是对于某些特定的 data 内容，lxml.etree.HTML 解析时会出现问题，导致程序进入无限循环，并且占用100%的CPU。

有没有人知道下面这个 data 中到底是什么导致了这个问题？更重要的是，我该如何防止这种情况在无数随机的、损坏的 data 中发生呢？

补充：结果发现这是 lxml 版本 2.7.8 及以下的一个bug（至少是这样）。我更新到了 lxml 2.9.0，问题就解决了。

补充：我知道这构成了一个无限循环，但这并不是我遇到的坏情况。对于健康的 data 内容，它运行得很好（虽然是无限循环）。但是对于不健康的 data 内容，比如下面这个，情况就不同了，循环会停止，内存会开始填满，当内存满了，所有的CPU就会进入等待状态。有关原始调试的信息，请查看这个问题。

#!/usr/bin/python
# -*- coding: utf-8 -*-
#

import sys
from lxml import etree



data = '''
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:og="http://opengraphprotocol.org/schema/" xmlns:fb="http://www.facebook.com/2008/fbml">
<head>
<meta charset="UTF-8">
    <title>The 20 Most Despicable Things Gordon Ramsay Has Said and Done, Ranked -- Grub Street New York</title>

    <link rel="alternate" type="application/rss+xml" title="RSS 2.0" href="http://feedproxy.google.com/nymag/grubstreet" />



    <meta name="Headline" content="The 20 Most Despicable Things Gordon Ramsay Has Said and Done, Ranked" />
    <meta name="keywords" content="april bloomfield, el gordo, frank bruni, gordon ramsay, lawsuits, lists, marcus samuelsson, mario batali, shitlist, spotted pig, sued" />

    <meta name="description" content="Racism, fat-shaming, and vegetarian trickery." />

    <meta name="Byline" content="Sierra Tishgart" />
    <meta name="Type_of_Feature" content="" />
    <meta name="Issue_Date" content="March  8, 2013 12:50 PM" />
    <meta name="related_stories" content="The 20 Most Despicable Things Gordon Ramsay Has Said and Done, Ranked" />
    <meta name="document_type" content="Blog" />
    <meta name="category" content="Lists" />

    <link rel="image_src" href="http://pixel.nymag.com/imgs/daily/grub/2013/03/08/08-gorgon-ramsay.o.jpg/a_146x97.jpg" />
    <link rel="canonical" href="http://newyork.grubstreet.com/2013/03/20-despicable-things-gordon-ramsay.html" id="canonical" />

    <script>
        var canonicalUrl = "http://newyork.grubstreet.com/2013/03/20-despicable-things-gordon-ramsay.html";
    </script>



    <meta name="content.tags.primary" content=";network - Grub Street,;city - New York City,;tag - lists" />
    <meta name="content.tags" content=";tag - april bloomfield,;tag - el gordo,;tag - frank bruni,;tag - gordon ramsay,;tag - lawsuits,;tag - marcus samuelsson,;tag - mario batali,;tag - shitlist,;tag - spotted pig,;tag - sued" />
    <meta name="content.hierarchy" content="New York City:Grub Street" />
    <meta name="content.type" content="Blog" />
    <meta name="content.subtype" content="Blog Entry" />    


    <meta property="fb:app_id" content="206283005644" />
    <meta property="og:title" content="The 20 Most Despicable Things Gordon Ramsay Has Said and Done, Ranked" />
    <meta property="og:description" content="Racism, fat-shaming, and vegetarian trickery." /> 
    <meta property="og:image" content="http://pixel.nymag.com/imgs/daily/grub/2013/03/08/08-gorgon-ramsay.o.jpg/a_146x97.jpg"/>
    <meta property="og:url" content="http://newyork.grubstreet.com/2013/03/20-despicable-things-gordon-ramsay.html" />
    <meta property="og:type" content="article" />
    <meta property="og:site_name" content="Grub Street New York" />





    <meta name="viewport" content="width=1020">

<link type="text/css" rel="stylesheet" href="http://cache.nymag.com/css/screen/grubstreet/grubstreet-core.css" media="all" />
<link type="text/css" rel="stylesheet" href="http://cache.nymag.com/css/screen/section/daily/slideshow.css" media="all" />
<link type="text/css" rel="stylesheet" href="http://cache.nymag.com/css/screen/echo.css" media="all" />
<link type="text/css" rel="stylesheet" href="http://cache.nymag.com/css/screen/loginRegister.css" media="all" />
<link rel="stylesheet" href="http://cache.nymag.com/css/screen/advertising.css" media="all" />
<link rel="shortcut icon" href="http://images.nymag.com/gfx/grubst/favicon.ico" />

<style type="text/css">
#adsplashtop,#pushdown {padding:5px 5px;}
#pushdown {border-top:1px solid #737373}
</style>











    <!--[if IE 6]>
    <link rel="stylesheet" href="http://cache.nymag.com/css/screen/grubstreet/win-ie6.css" type="text/css" media="screen, projection" />
<![endif]-->

<!--[if IE 7]>
    <link rel="stylesheet" href="http://cache.nymag.com/css/screen/grubstreet/win-ie7.css" type="text/css" media="screen, projection" />
<![endif]-->




    <script type="text/javascript">
        var NYM = {};
        NYM.config = {};
        NYM.config.membership = {
            "service":"nym"
        };
        NYM.config.advertising = {
            "sitename":"nym.grubstreet"
        };

    </script>




<script type="text/javascript">
    var date = 'March 12, 2013 12:42:38';
    var currDate=new Date(date);
    var GRUBST = {};
    if (!NYM) {  
        var NYM = {};
        NYM.config = {};
        NYM.config.membership = {
            "service":"nym"
        };
        NYM.config.advertising = {
             "sitename":"nym.grubstreet"
        };
    }
</script>
<script type="text/javascript" src="http://cache.nymag.com/scripts/modernizr-1.7.min.js"></script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript" src="http://cache.nymag.com/scripts/jquery-ui-1.8.2.custom.min.js"></script>
<script type="text/javascript" src="http://cache.nymag.com/scripts/ad_manager.js"></script>
<script type="text/javascript" src="http://cache.nymag.com/js/2/global.js"></script>
<script type="text/javascript" src="http://cache.nymag.com/scripts/skinTakeover.js"></script>
<script type="text/javascript" src="http://cache.nymag.com/scripts/grubstreet-controls.js"></scr
'''







n = 0
while True:
    n += 1

    tree = etree.HTML( data )
    m = tree.xpath("//meta[@property]")

    print '-', n 
    for i in m:
        print n 
        #print (i.attrib['property'], i.attrib['content'])

如果想要快速解决，可以使用：

import sys
from lxml import etree

print("%-20s: %s" % ('Python',           sys.version_info))
print("%-20s: %s" % ('lxml.etree',       etree.LXML_VERSION))
print("%-20s: %s" % ('libxml used',      etree.LIBXML_VERSION))
print("%-20s: %s" % ('libxml compiled',  etree.LIBXML_COMPILED_VERSION))
print("%-20s: %s" % ('libxslt used',     etree.LIBXSLT_VERSION))
print("%-20s: %s" % ('libxslt compiled', etree.LIBXSLT_COMPILED_VERSION))

我得到了：

OS                  : Ubuntu 12.10 (AWS)
Python              : sys.version_info(major=2, minor=7, micro=3, releaselevel='final', serial=0)
lxml.etree          : (3, 1, 0, 0)
libxml used         : (2, 7, 8)
libxml compiled     : (2, 7, 8)
libxslt used        : (1, 1, 26)
libxslt compiled    : (1, 1, 26)

错误处理内存管理 lxml html解析版本更新无限循环数据完整性 CPU占用

如何防止 lxml.etree.HTML(data) 在特定数据类型上崩溃？

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