Dnspython模块
1.模块域名解析方法
A记录，主机名转换成IP地址
MX记录，邮件交换记录，定义邮件服务器的域名
CNAME记录，别名记录，实现域名间的映射
NS记录，标记区域的域名服务器及授权子域
PTR记录，反向解析，与A记录相反，将IP转换成主机名
SOA记录，SOA标记，一个起始授权区的定义
2.常见解析类型示例说明
实现A记录的查询方法
import dns.resolver
domain = raw_input(‘Please input an domain:‘)
A = dns.resolver.query(domain,‘A‘)
for i in A.response.answer:
for j in i.items:
print j.address
220.181.111.86
123.125.114.144
220.181.111.85
MX记录
import dns.resolver
domain = raw_input(‘Please input an domain:‘)
MX = dns.resolver.query(domain,‘MX‘)
for i in MX:
print ‘MX preference =‘,i.preference,‘mail exchanger =‘,i.exchange
MX preference = 20 mail exchanger = jpmx.baidu.com.
MX preference = 20 mail exchanger = mx50.baidu.com.
MX preference = 10 mail exchanger = mx.n.shifen.com.
MX preference = 20 mail exchanger = mx1.baidu.com.
NS记录
import dns.resolver
domain = raw_input(‘Please input an domain:‘)
ns = dns.resolver.query(domain,‘NS‘)
for i in ns.response.answer:
for j in i.items:
print j.to_text()
ns4.baidu.com.
dns.baidu.com.
ns7.baidu.com.
ns2.baidu.com.
ns3.baidu.com.
CNAME记录
import dns.resolver
domain = raw_input(‘Please input an domain:‘)
cname = dns.resolver.query(domain,‘CNAME‘)
for i in cname.response.answer:
for j in i.items:
print j.to_text()
2.DNS域名轮询业务监控
大部分的DNS解析都是一个域名对应一个IP，但通过DNS轮询技术可以做到一个域名对应多个IP，从而实现最简单且高效的负载均衡，不过此方案的最大弊端是目标主机不可用时无法被自动剔除，因此做好业务主机的服务可监控至关重要。本示例通过分析天谴域名的解析IP，再结合服务端口探测来实现自动监控，在域名解析中添加、删除IP时，无须对监控脚本进行修改。
（1）步骤
实现域名的解析，获取域名所有的A记录解析IP列表
对IP列表进行HTTP级别的探测
#!/usr/bin/env python
import dns.resolver
import os
import httplib
iplist = []
appdomain = ‘163.com‘
def get_iplist(domain = ""):
try:
A = dns.resolver.query(domain,‘A‘)
except Exception,e:
print "dns resolver error:" + str(e)
return
for i in A.response.answer:
for j in i.items:
iplist.append(j.address)
return True
def checkip(ip):
checkurl = ip+":80"
getcontent = ""
httplib.socket.setdefaulttimeout(5)
conn = httplib.HTTPConnection(checkurl)
try:
conn.request("GET","/",headers = {"Host": appdomain})
r = conn.getresponse()
getcontent = r.read(15)
finally:
if getcontent == "<!doctype html>":
print ip + "[OK]"
else:
print ip + "[Error]"
if __name__ == "__main__":
if get_iplist(appdomain) and len(iplist) > 0:
for ip in iplist:
checkip(ip)
else:
print "dns resolver error."