调用微信支付或者支付宝验签的时候会很慢，发现程序没有问题，主要是请求到返回这段时间太长。
具体如下： prepayInfo->prepay response 大概用了6秒的时间
优化前
[08 14:10:51,081 INFO ] [http--8081-3$598667353] util.WxmppayUtil - Wxmppay source str:
[08 14:10:51,171 INFO ] [http--8081-3$598667353] util.WxmppayUtil - Wxmppay xml str:
[08 14:10:51,171 INFO ] [http--8081-3$598667353] util.WxmppayUtil - Wxpay request prepayInfo:
[08 14:10:56,779 INFO ] [http--8081-3$598667353] util.WxmppayUtil - WX prepay response:
[08 14:10:56,800 INFO ] [http--8081-3$598667353] util.WxmppayUtil - Wxpay prepay id str: wx2017020814105685b74eb4c00453577375
[08 14:10:56,800 INFO ] [http--8081-3$598667353] util.WxmppayUtil - Wxmppay source str: appId=wx9006127d7b209213&nonceStr=dcdgdihjeccjdehbagaihfficgbagaei&package=prepay_id=wx2017020814105685b74eb4c00453577375&signType=MD5&timeStamp=1486534256&key=j5oSq7yOVet9DiWWZOcSTbqzm1KhKOZZ
安装nslook dig tcpdump 工具查看域名解析部分
yum install bind-utils
yum install tcpdump
[root@localhost opt]# dig www.baidu.com
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6_8.4 <<>> www.baidu.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16260
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.baidu.com. IN A
;; ANSWER SECTION:
www.baidu.com. 975 IN CNAME www.a.shifen.com.
www.a.shifen.com. 22 IN A 220.181.112.244
www.a.shifen.com. 22 IN A 220.181.111.188
;; Query time: 0 msec
;; SERVER: 218.30.26.68#53(218.30.26.68)
;; WHEN: Wed Feb 8 14:21:15 2017
;; MSG SIZE rcvd: 90
[root@localhost opt]# dig api.mch.weixin.qq.com
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6_8.4 <<>> api.mch.weixin.qq.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49081
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;api.mch.weixin.qq.com. IN A
;; ANSWER SECTION:
api.mch.weixin.qq.com. 123 IN CNAME forward.qq.com.
forward.qq.com. 76 IN A 123.151.79.109
forward.qq.com. 76 IN A 123.151.71.149
;; Query time: 1 msec
;; SERVER: 218.30.26.68#53(218.30.26.68)
;; WHEN: Wed Feb 8 14:21:42 2017
;; MSG SIZE rcvd: 93
[root@localhost opt]# nslookup api.mch.weixin.qq.com
Server: 218.30.26.68
Address: 218.30.26.68#53
Non-authoritative answer:
api.mch.weixin.qq.com canonical name = forward.qq.com.
Name: forward.qq.com
Address: 123.151.79.109
Name: forward.qq.com
Address: 123.151.71.149
[root@localhost opt]# nslookup www.baidu.com
Server: 218.30.26.68
Address: 218.30.26.68#53
Non-authoritative answer:
www.baidu.com canonical name = www.a.shifen.com.
Name: www.a.shifen.com
Address: 220.181.112.244
Name: www.a.shifen.com
Address: 220.181.111.188
通过wget分析域名解析的时间， 发现每次都会去域名服务器解析。
具体功过查看dns查询包
tcpdump -i eth1 host 8.8.8.8 -X -e -nn
后来安装本地域名缓存， centos下安装命令如下：
yum install nscd
vim /etc/nscd.conf
service nscd status
service nscd restart
安装后通过wget再次访问时速度明显加快， 但是通过程序来访问还是很慢。
代码中是通过来发送请求的， PoolingHttpClientConnectionManager 初始化没有传入DnsResolver，默认使用的是 SystemDefaultDnsResolver，具体代码如下：
public static final SystemDefaultDnsResolver INSTANCE = new SystemDefaultDnsResolver();
@Override
public InetAddress[] resolve(final String host) throws UnknownHostException {
return InetAddress.getAllByName(host);
}
看到上面代码最终是调用 InerAddress.getAllByName(host); 方法
优化后
[08 16:12:02,539 INFO ] [http--8081-11$762658730] util.WxmppayUtil - Wxmppay source str:
[08 16:12:02,540 INFO ] [http--8081-11$762658730] util.WxmppayUtil - Wxmppay xml str:
[08 16:12:02,541 INFO ] [http--8081-11$762658730] util.WxmppayUtil - Wxpay request prepayInfo:
[08 16:12:02,542 INFO ] [http--8081-11$762658730] util.CwCachedDnsResolver - get address from cached dns
[08 16:12:02,806 INFO ] [http--8081-11$762658730] util.WxmppayUtil - WX prepay response:
[08 16:12:02,811 INFO ] [http--8081-11$762658730] util.WxmppayUtil - Wxpay prepay id str: wx20170208161202b47a6324710779458744
[08 16:12:02,811 INFO ] [http--8081-11$762658730] util.WxmppayUtil - Wxmppay source str: