最近碰到一个问题，在测试CDN缓存，每次上传更新一个同名文件，CDN后台并未做刷新缓存动作，但依旧能下载到新的文件，此时发现其实每次解析出来CDN节点都有很多个，怀疑我每次下载用的是不同的节点如下：
root@pc:~# nslookup cos.lejunwl.com
Server: 127.0.0.53
Address: 127.0.0.53#53
Non-authoritative answer:
cos.lejunwl.com canonical name = cos.lejunwl.com.cdn.dnsv1.com.
cos.lejunwl.com.cdn.dnsv1.com canonical name = 2009447.dispatch.spcdntip.com.
Name: 2009447.dispatch.spcdntip.com
Address: 113.105.155.213
Name: 2009447.dispatch.spcdntip.com
Address: 180.96.32.98
所以不用刷新也是最新的，为了验证是不是这个问题，我用curl 工具指定ip进行访问命令如下：
curl -x 113.105.155.213:80 http://cos.lejunwl.com/youlong/test/425YX/XZSDKDEMO1110/XZSDKDEMO1110_hcFaLHQuX8FilfhckAWJpw.apk -O -v
* Trying 113.105.155.213...
* TCP_NODELAY set
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Connected to 113.105.155.213 (113.105.155.213) port 80 (#0)
> GET http://cos.lejunwl.com/youlong/test/425YX/XZSDKDEMO1110/XZSDKDEMO1110_hcFaLHQuX8FilfhckAWJpw.apk HTTP/1.1
> Host: cos.lejunwl.com
> User-Agent: curl/7.58.0
> Accept: */*
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 200 OK
< Server: NWS_SP
< Connection: keep-alive
< Date: Sat, 12 Oct 2019 07:42:12 GMT
< Cache-Control: max-age=600
< Expires: Sat, 12 Oct 2019 07:52:12 GMT
< Last-Modified: Sat, 12 Oct 2019 15:29:07 GMT
< Content-Type: application/vnd.android.package-archive
< Content-Length: 3795490
< X-NWS-LOG-UUID: 5459280831822939693 2107abdde3874148c4be187298eb91fe
< X-Cache-Lookup: Hit From Disktank3
< Accept-Ranges: bytes
<
{ [2600 bytes data]
100 3706k 100 3706k 0 0 582k 0 0:00:06 0:00:06 --:--:-- 585k
* Connection #0 to host 113.105.155.213 left intact
再通过md5sum 进行比对
root@pc:~# md5sum XZSDKDEMO1110_hcFaLHQuX8FilfhckAWJpw.apk
e2560de9dfd5138607b6590080c35d65 XZSDKDEMO1110_hcFaLHQuX8FilfhckAWJpw.apk
这样就可以比对出在同一个CDN节点同名文件有没有被覆盖。