代码执行结果

Question

我写了一些查询adns的代码。这段代码的问题是它被卡住了，怎么样？让我解释一下：

说我的dnslist是[“8.8.4.4”，“8.8.8.8”，“208.67.220.220”，“208.67.222.222”，“192.168.50.1”]
它会从列表中弹出一个dns并再次查询它，现在这意味着将以相反的顺序查询DNS
无论我做什么，它都不会显示它首先拾取的dns的结果（在我们的例子中为192.168.50.1）
我不确定dns是否曾这样回复过
- 首先，我更改了DNS列表以包含最后一个DNS服务器并且代码执行正常
- 其次我使用旧的列表和5个DNS服务器，除了最后一个是由我管理的，所以我可以跟踪代码是否查询它，我惊讶地发生了查询。
- 所以进行查询，我们得到结果，但结果从未因某种原因插入到resolved_hosts中，并且由于未插入结果，其长度将保持小于dnslist的长度，从而导致无限循环。

您认为可能导致此问题以及如何解决该问题？

代码执行结果

Inside class's init'
Data
host www.yahoo.com
dnslist length 5
intensity 1
Inside resolve()
inside finished_resolving()
Resolved : 0/5
Inside 'while not finished_resolving'
Queue: 0/1
Launching Querying for www.yahoo.com/1 on 192.168.50.1
Queue: 1/1
Launching Querying for www.yahoo.com/1 on 208.67.222.222
inside collect_results()
inside finished_resolving()
Resolved : 0/5
Inside 'while not finished_resolving'
------------------------ CLIPPED ----------------
Inside 'while not finished_resolving'
inside collect_results()
Inside collect_results's for query in self.adns.completed()
DNS used was208.67.222.222
Answered : (0, 'any-fp.wa1.b.yahoo.com', 1286169807, ('69.147.125.65', '67.195.160.76'))
Resolved www.yahoo.com to 69.147.125.65 using 208.67.222.222
Resolved hosts count1
And they are: 
{'208.67.222.222': '69.147.125.65'}


inside finished_resolving()
Resolved : 1/5
Inside 'while not finished_resolving'
Queue: 1/1
Launching Querying for www.yahoo.com/1 on 208.67.220.220
inside collect_results()
inside finished_resolving()
Resolved : 1/5
Inside 'while not finished_resolving'
-------------------------- CLIPPED --------------------
inside collect_results()
Inside collect_results's for query in self.adns.completed()
DNS used was208.67.220.220
Answered : (0, 'any-fp.wa1.b.yahoo.com', 1286169790, ('67.195.160.76', '69.147.125.65'))
Resolved www.yahoo.com to 67.195.160.76 using 208.67.220.220
Resolved hosts count2
And they are: 
{'208.67.222.222': '69.147.125.65', '208.67.220.220': '67.195.160.76'}


inside finished_resolving()
Resolved : 2/5
Inside 'while not finished_resolving'
Queue: 1/1
Launching Querying for www.yahoo.com/1 on 8.8.8.8
inside collect_results()
inside finished_resolving()
Resolved : 2/5
Inside 'while not finished_resolving'
-------------------------- CLIPPED --------------------
inside collect_results()
Inside collect_results's for query in self.adns.completed()
DNS used was8.8.8.8
Answered : (0, 'eu-fp.wa1.b.yahoo.com', 1286169758, ('87.248.122.122',))
Resolved www.yahoo.com to 87.248.122.122 using 8.8.8.8
Resolved hosts count3
And they are: 
{'208.67.222.222': '69.147.125.65', '208.67.220.220': '67.195.160.76', '8.8.8.8': '87.248.122.122'}


inside finished_resolving()
Resolved : 3/5
Inside 'while not finished_resolving'
Queue: 1/1
Launching Querying for www.yahoo.com/1 on 8.8.4.4
inside collect_results()
inside finished_resolving()
Resolved : 3/5
Inside 'while not finished_resolving'
-------------------- CLIPPED -------------------------------------
inside collect_results()
Inside collect_results's for query in self.adns.completed()
DNS used was8.8.4.4
Answered : (0, 'eu-fp.wa1.b.yahoo.com', 1286169757, ('87.248.122.122',))
Resolved www.yahoo.com to 87.248.122.122 using 8.8.4.4
Resolved hosts count4
And they are: 
{'208.67.222.222': '69.147.125.65', '208.67.220.220': '67.195.160.76', '8.8.8.8': '87.248.122.122', '8.8.4.4': '87.248.122.122'}


inside finished_resolving()
Resolved : 4/5
Inside 'while not finished_resolving'
inside collect_results()
inside finished_resolving()
Resolved : 4/5
---------------- CLIPPED -------------------------------

（最后一个块不断重复，直到系统开始挂起，加载到24）

代码

test.py

import adns
from time import time
from async_dns import AsyncResolver



dnslist2 = ["8.8.4.4", "8.8.8.8", "208.67.220.220", "208.67.222.222", "192.168.50.1"]  #192.168.50.1  is a dns server i manage
host = "www.yahoo.com"
record = adns.rr.A
intensity = len(dnslist2)/5+1

ar = AsyncResolver(dnslist2, host, record, intensity)
start = time()
resolved = ar.resolve()
end = time()

print "\n\n"

for dns, ip in resolved.items():
  if ip is None:
    print "%s could not resolv %s." % (dns, host)
  else:
    print "%s resolved it to %s : %s" % (dns, host, ip)

print "\n\n----------------------------------------------------"
print "It took %.2f seconds to query %d dns." % (end-start, len(dnslist))
print "----------------------------------------------------"

async_dns.py

#!/usr/bin/python
#

import sys
import adns
from time import time

class AsyncResolver(object):
    def __init__(self, dnslist, host, record, intensity=10):

        """
        dnslist: a list of dns used to resolve
        host : hostname to resolve
        record: recordtype to resolve
        intensity: how many hosts to resolve at once
        """
        print "Inside class's init'"
        self.dnslist = dnslist
        self.host = host
        self.record = record


        if intensity >= len(dnslist) :
            self.intensity = len(dnslist)/5+1
        else:
            self.intensity = intensity

        print "Data"
        print "host " + host
        print "dnslist length " + str(len(dnslist))
        print "intensity " + str(intensity)




    def resolve(self):
        """ Resolves hosts and returns a dictionary of { 'dns': 'ip' }. """
        print "Inside resolve()"

        host = self.host
        record = self.record
        resolved_hosts = {}
        active_queries = {}
        dns_queue = self.dnslist[:]

        def collect_results():
            print "inside collect_results()"
            for query in self.adns.completed():
                print "Inside collect_results's for query in self.adns.completed()"
                answer = query.check()
                dns = active_queries[query]
                print "DNS used was" + dns
                print "Answered : " + str(answer)
                del active_queries[query]
                if answer[0] == 0:
                    #print "Inside answer[0] == 0 , ip:" + answer[3][0]
                    ip = answer[3][0]
                    resolved_hosts[dns] = ip
                    print "Resolved %s to %s using %s" % (host, ip, dns)
                    print "Resolved hosts count" + str(len(resolved_hosts))
                    print "And they are: "
                    print str(resolved_hosts)
                    print "\n"

                elif answer[0] == 101 and not record == adns.rr.CNAME: # CNAME if CNAME wasn't required'
                    print "ooopppps, i got a CNAME, gotta find its A"
                    print "\n"
                    query = self.adns.submit(answer[1], adns.rr.A)
                    active_queries[query] = dns
                else:
                    resolved_hosts[dns] = None
                    print "THIS COULD NOT BE RESOLVED"

        def finished_resolving():
            print "inside finished_resolving()"
            print "Resolved : " + str(len(resolved_hosts)) + "/" + str(len(self.dnslist))
            return len(resolved_hosts) == len(self.dnslist)

        while not finished_resolving():
            print "Inside 'while not finished_resolving'"
            while dns_queue and len(active_queries) <= self.intensity:
                print "Queue: " + str(len(active_queries)) + "/" + str(self.intensity)
                dns = dns_queue.pop()
                self.adns = adns.init(adns.iflags.noautosys,sys.stderr,"nameserver "+dns)
                query = self.adns.submit(host, record)
                print "Launching Querying for " + host + "/" + str(record) + " on " + dns
                active_queries[query] = dns
            collect_results()
        return resolved_hosts

Answer 1

我刚刚尝试使用adns python绑定并遇到了类似的问题 - 完成的查询数组永远不会被完全填充，导致检查循环永远运行。在我的情况下，似乎无法解析的域（由于NXDOMAIN等）从未添加到已完成的查询数组（具有空/ Null值）

我查看了C绑定，但看不到用于保存失败结果的单独数据结构，所以看起来这些应该以某种方式添加到“已完成”的查询中。我怀疑绑定或adns库中存在阻止这种情况发生的错误。

Answer 2

只要while not finished_resolving()返回True，您的finished_resolving()循环就会显着继续。该功能只是比较len(resolved_hosts)和len(self.dnslist)。但是，据我所知，你永远不会改变循环中任何一个变量的长度，所以它将永远持续下去。

评论后编辑这两个块中的任何一个都不会影响两个变量中任何一个的长度。请解释一下您认为他们的变化情况。

Python和ADNS，在某个地方陷入无限循环

代码执行结果

代码

2 个答案: