反向代理：缓存

http/1.1
RFC
http/1.1《-----http/1.0
cache
http协议：
request:
method url version
HEADERS

     BODY
 response:
      version status reason
      HEADERS

     BODY

 首部：
     通用
         Connection:close|keep-alive
         Date：日期时间
         Host：请求的主机
         Pragma：no-cahce
         Via：请求或响应在客户端和服务器之间传递时所经过的代理
         Transfer-Encoding：消息主体的传输编码方式，chunked表示采用块编码的方式
     请求
         If-Modified-Since
         If-None-Match
         Referer
         User-Agent

         Host:请求的主机
         Accept-Encoding:接受的编码方式
         Accept-Language:接受的自然语言
         Accep-Charset:接受字符集
         Authorization:服务端发送www-authenticate时，客户端通过此首部提供认证信息

     响应
        ETag:内容的标签
        Location:重定向后的新位置
        Server:服务器软件信息
        WWW-Authenticate:要求对客户端进行认证

     实体
         Content-Encoding
         Content-Language
         Conten-Lenth
         Content-Type:内容的MIME格式
         Expires
         Last-Modified

web object

browser：缓存机制
本地：

公共缓存（public）
私有缓存（private）

expire（过期时间）：2016-05-21 14:55:31
cache-control：max-age=600
etag（标识符）：一个时间随机生成数
last-mofified：
if-modified-since：
if-none-match：
vary：
age：

index.html：14:55:59

14:55:59,0000011：

条件式判断机制

CDN（content delivery network）：内容分发网络，一组缓存服务器组成的网络（集群）

www.maoshou.com in CNAME cache1.cdn.com
www.maoshou.com in CNAME cache4.cdn.com

bind，view
bind-dlz+MySQL
pgsql，oracle，db4

Varnish:
web缓存、代理服务器；

squid：varnish
httpd：nginx

nginx+varnish
nginx+squid

varnish配置要自己去编写配置文件：采用vcl编写工具

状态引擎：子例程，函数，可以使用return()函数返回状态给varnish进程
vcl_recv
vcl_pass
vcl_hash
vcl_hit
vcl_deliver
vcl_miss
vcl_fetch
vcl_deliver
安装配置：

源始服务器：node2
varnish节点：node1（两块网卡）

node2:
yum install php php-mysql mysql-server
ifconfig eht0 192.168.20.12/24 up

vim /var/www/html/index.html

node2.magedu.com


service httpd restart

node1:
ifconfig eth0 192.168.100.7/24 up
ifconfig eth1 192.168.20.1/24 up
yum install varnish
rpm -ql varnish
vim /etc/sysconfig/varnish
VARNISH_LISTEN=80
VARNISH_STORAGE="malloc,100M"

service varnish start
cd /etc/varnish
vim test.vcl
backend websrv1 {
.host = "192.168.20.12";
.port = "80";
}
让自己写的配置文件生效：
vim /etc/sysconfig/varnish
VARNISH_VCL_CONF=/etc/varnish/test.vcl
或者varnishadm -S /etc/varnish/secret -T 127.0.0.1:6082
help
ping
status
stats
vcl.list
vcl.show boot
vcl.load test1 /etc/varnish/test.vcl
vcl.list
vcl.use test1
vcl.show test1

http://172.16.100.7
curl -I http://192.168.100.7

vim test.vcl
sub vcl_deliver {
if (obj.hits > 0) {
set resp.http.X-Cache = "HIT";
} else {
set resp.http.X-Cache = "MISS";
}
}

vcl.load test2 /etc/varnish/test.vcl
vcl.use test2
vcl.show test2

curl -I http://172.16.100.7
crul -I http://172.16.100.7/index.html

node2:
cd /var/www/html
vim test.html

test on node2.magedu.com

curl -I http://172.16.100.7/test.html

node1:
vim test.vcl
sub vcl_deliver {
if (obj.hits > 0) {
set resp.http.X-Cache = "HIT from "server.ip;
} else {
set resp.http.X-Cache = "MISS";
}
}

vcl.load test3 /etc/varnish/test.vcl
vcl.use test3
vcl.show test3

vcl -I http://172.16.100.7/test.html

vim test.vcl
sub vcl_recv {
if (req.url ~ "test.html") {
return(pass);
}
return(lookup);
}

vcl.load test4 /etc/varnish/test.vcl
vcl.use test4

curl -I http://172.16.100.7/index.html
curl -I http://172.16.100.7/test.html

vim test.vcl
sub vcl_fetch {
if (req.url ~ ".(jpg|jpeg|gif|png)$") {
set beresp.ttl = 7200s;
}
if (req.url ~ ".(html|css|js)$")
set beresp.ttl = 1200s;
}
}

vcl.load test5 /etc/varnish/test.vcl
vcl.use test5
curl -I http://172.16.100.7/index.html

删除缓存：
vim test.vcl
acl purgers {
"127.0.0.1";
"172.16.0.0"/16;
}
sub vcl_recv {
if (req.request == "PURGE") {
if (!client.ip ~ purgers) {
error 405 "Method not allowed";
}
}
if (req.url ~ "test.html") {
return(pass);
}
return(lookup);
}
sub vcl_hit {
if (req.request == "PURGE") {
purge;
error 200 "purged ok";
}
}
sub vcl_miss {
if (req.request == "PURGE") {
purge;
error 404 "not in cache";
}
}
sub vcl_pass {
if (req.request == "PURGE") {
error 502 "purged on a passed object";
}
}

vcl.load test6 /etc/varnish/test.vcl
vcl.use test6
curl -I http://172.16.100.7/index.html
curl -X PURGE http://172.16.100.7/index.html

多台后端主机的健康状况检查:（node2和node3）
ifconfig eth0 192.168.20.13/24 up

node1:
vim test.vcl
backend web1 {
.host = "192.168.20.12";
.port = "80";
}
director wesrvs random {
{
.backend = web1;
.weight = 2;
}
{
.backend = {
.host = "192.168.20.13";
.port = "80";
}
weight = 1;
}
}
或者：
backend web1 {
.host = "192.168.20.12";
.port = "80";
.probe = { (让该节点离线)
.url = "/index.html";
.window = 5;
.threshold = 2;
.interval = 3s;
}
}
backend web2 {
.host = "192.168.20.13";
.port = "80";
}
director websrvs random {
{
.backend = web1;
.weight = 2;
}
{
.backend = web2;
.weight = 1;
}
}
sub vcl_recv {
set req.backend = websrvs;
if (req.request == "PURGE") {
if (!client.ip ~ purgers) {
error 405 "Method not allowed";
}
}
if (req.url ~ "test.html") {
return(pass);
}
return(lookup);
}

vcl.load test7 test.vcl
vcl.use test7
curl http://172.16.100.7/index.html

请求不同内容时，转发至不同主机：
vim test.vcl
把director那一栏全部注释
sub vcl_recv {
if (req.url ~ ".(html|css|js)$") {
set req.backend = web1;
} else {
set req.backend = web2;
}
if (req.request == "PURGE") {
if (!client.ip ~ purgers) {
error 405 "Method not allowed";
}
}
if (req.url ~ "test.html") {
return(pass);
}
return(lookup);
}

vcl.load test8 test.vcl
vcl.use test8