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本文为系列测试文章，拟基于自签名证书认证的etcd容器来构建coredns域名解析系统。

一、前置文章

构建后端为etcd的CoreDNS的容器集群（一）、生成自签名证书

构建后端为etcd的CoreDNS的容器集群（二）、下载最新的etcd容器镜像

构建后端为etcd的CoreDNS的容器集群（三）、etcd功能测试

构建后端为etcd的CoreDNS的容器集群（四）、etcd挂载私有自签名证书进行访问测试

构建后端为etcd的CoreDNS的容器集群（五）、coredns对接etcd测试

二、本次任务目标

 coredns对接了etcd数据库，本次尝试编写一段脚本，通过fping命令检查远端服务器的存活状态，域名假定为www.test.com，ip假定为192.168.1.168，如果ip存活，则检查etcd数据库有无此记录，没有则添加；如IP不存活，则检查etcd数据库中有无此记录，有则删除。同时为了避免在网络异常时域名记录被完全清除，在操作前增加一个对本地网关的检查，如果fping本地网关不通的时候才扫行域名记录的增、删操作，如果网关fping异常则不做任何操作。

三、代码编写

本任务代码如下：

[root@localhost etcd]# cat auto_main_domain.sh 
#!/bin/bash  
##__author__='daigjianbing'DOMAIN="www.test.com"  
IP="192.168.80.135"  
GATEWAY="192.168.80.135"  
ETCD_KEY="/coredns/com/test/www"  
ETCD_VALUE='{"host":"192.168.80.135","ttl":10}'
ETCD_ENDPOINT="https://etcd-1:2379"  # 根据实际情况调整etcd的端点  
ETCD_CERT="/opt/etcd/ssl/etcd.pem"  # 如果etcd使用了TLS证书，请指定证书路径，否则留空
ETCD_KEY_FILE="/opt/etcd/ssl/etcd-key.pem"  # 如果etcd使用了TLS密钥文件，请指定密钥文件路径，否则留空
ETCD_CACERT="/opt/etcd/ssl/ca.pem"  # 如果etcd使用了CA证书，请指定CA证书路径，否则留空# 检查本地网关存活状态  
if ! fping -c 1 $GATEWAY &> /dev/null; then  echo "Gateway $GATEWAY is not reachable. Skipping further operations."  exit 1  
else  echo "Gateway $GATEWAY is reachable."  
fi  # 检查IP存活状态  
if fping -c 1 $IP &> /dev/null; then  echo "IP $IP is alive."  # 检查etcd中是否有记录  itemcheck=`/opt/etcd/etcdctl --endpoints=$ETCD_ENDPOINT --cert=$ETCD_CERT --key=$ETCD_KEY_FILE --cacert=$ETCD_CACERT get $ETCD_KEY | grep $ETCD_KEY |wc -l`if [ ${itemcheck} -eq 0 ]; then  echo "Record for $DOMAIN ($IP) does not exist in etcd. Adding..."  /opt/etcd/etcdctl --endpoints=$ETCD_ENDPOINT --cert=$ETCD_CERT --key=$ETCD_KEY_FILE --cacert=$ETCD_CACERT put $ETCD_KEY $ETCD_VALUE  if [ $? -eq 0 ]; then  echo "Record added successfully."  else  echo "Failed to add record."  fi  else  echo "Record for $DOMAIN ($IP) already exists in etcd."  fi  
else  echo "IP $IP is not alive."  # 检查etcd中是否有记录  itemcheck=`/opt/etcd/etcdctl --endpoints=$ETCD_ENDPOINT --cert=$ETCD_CERT --key=$ETCD_KEY_FILE --cacert=$ETCD_CACERT get $ETCD_KEY | grep $ETCD_KEY |wc -l`if [ $itemcheck -ne 0 ]; then  echo "Record for $DOMAIN ($IP) exists in etcd. Deleting..."  /opt/etcd/etcdctl --endpoints=$ETCD_ENDPOINT --cert=$ETCD_CERT --key=$ETCD_KEY_FILE --cacert=$ETCD_CACERT del $ETCD_KEY  if [ $? -eq 0 ]; then  echo "Record deleted successfully."  else  echo "Failed to delete record."  fi  else  echo "Record for $DOMAIN ($IP) does not exist in etcd."  fi  
fi
[root@localhost etcd]# 

四、IP正常测试

1、清空域名解析数据库记录

[root@localhost etcd]# ./etcdctl --endpoints=https://etcd-1:2379  --cacert ssl/ca.pem --cert ssl/etcd.pem  --key ssl/etcd-key.pem del --prefix "/" 
3
[root@localhost etcd]# ./etcdctl --endpoints=https://etcd-1:2379  --cacert ssl/ca.pem --cert ssl/etcd.pem  --key ssl/etcd-key.pem get --prefix "/" 
[root@localhost etcd]# 

可以看到当前已无域名记录。

2、运行程序

[root@localhost etcd]# sh auto_main_domain.sh   
Gateway 192.168.80.135 is reachable.
IP 192.168.80.135 is alive.
Record for www.test.com (192.168.80.135) does not exist in etcd. Adding...
OK
Record added successfully.
[root@localhost etcd]# ./etcdctl --endpoints=https://etcd-1:2379  --cacert ssl/ca.pem --cert ssl/etcd.pem  --key ssl/etcd-key.pem get --prefix "/" 
/coredns/com/test/www
{"host":"192.168.80.135","ttl":10}

3、验证解析

[root@localhost etcd]# nslookup www.test.com 127.0.0.1
Server:         127.0.0.1
Address:        127.0.0.1#53Name:   www.test.com
Address: 192.168.80.135
** server can't find www.test.com: NXDOMAIN[root@localhost etcd]# 

可以看到域名解析正常

四、异常测试

1、测试准备

本次异常测试因测试地址就是本机IP，无法设置不能访问，因此采用仅修改域名对应检查IP的方式来进行，修改原脚本中的IP值为当前无法访问的ip

 2、实际测试

[root@localhost etcd]# sh auto_main_domain.sh 
Gateway 192.168.80.135 is reachable.
IP 192.168.80.136 is not alive.
Record for www.test.com (192.168.80.136) exists in etcd. Deleting...
1
Record deleted successfully.[root@localhost etcd]# ./etcdctl --endpoints=https://etcd-1:2379  --cacert ssl/ca.pem --cert ssl/etcd.pem  --key ssl/etcd-key.pem get --prefix "/" 
[root@localhost etcd]#
[root@localhost etcd]# nslookup www.test.com 127.0.0.1
Server:         127.0.0.1
Address:        127.0.0.1#53** server can't find www.test.com: NXDOMAIN[root@localhost etcd]# 

可以看到，相关域名记录已自动删除，解析已无结果。

五、总结

通过上述代码，可以根据后端服务器IP的存活情况对域名进行动态管理，结合单域名多IP，可以实现域名IP智能化分发。