Linux(企业级)—— CDN

??与haproxy类似，CDN也可以作为反向代理器，支持健康检测与负载均衡等。

1. varnish安装

所需安装依赖性等：

jemalloc-3.6.0-1.el7.x86_64.rpm
jemalloc-devel-3.6.0-1.el7.x86_64.rpm 
varnish-4.0.5-1.el7.x86_64.rpm 
varnish-libs-4.0.5-1.el7.x86_64.rpm

2. 配置

实验环境;

CDN实现负载均衡，反向代理等
client:172.25.52.250 -> server1(CDN):172.25.52.1 -> 
server2(webserver1):172.25.52.2 |  server4(webserver3):172.25.52.4 
www.westos.org
server3(webserver2):172.25.52.3
bbs.westos.org

pam热插拔限制：
在这里插入图片描述

设置监听端口;
vim varnish.params 在这里插入图片描述

配置文件：
vim default.vcl

# Marker to tell the VCL compiler that this VCL has been adapted to the
# new 4.0 format.
vcl 4.0;

probe backend_healthcheck {
    .url = "/index.html";
    .window = 3;
    .threshold = 2;
    .interval = 3s;
}


# Default backend definition. Set this to point to your content server.
backend webserver1 {
    .host = "172.25.52.2";
    .port = "80";
    .probe = backend_healthcheck;

}
backend webserver2 {
    .host = "172.25.52.3";
    .port = "80";
    .probe = backend_healthcheck;
}
backend webserver3 {
    .host = "172.25.52.4";
    .port = "80";
    .probe = backend_healthcheck;
}

import directors;
sub vcl_init {
        new web_cluster = directors.round_robin();
        web_cluster.add_backend(webserver1);
        web_cluster.add_backend(webserver3);
}

sub vcl_recv {
    # Happens before we check if we have this in cache already.
    #
    # Typically you clean up the request here, removing cookies you don't need,
    # rewriting the request, etc.
	if (req.http.host ~ "^(www.)?westos.org") {
                set req.http.host = "www.westos.org";
                set req.backend_hint = web_cluster.backend();
                return(pass); #不缓存数据，直接访问后端主机
        }
        elseif (req.http.host ~ "^bbs.westos.org") {
                set req.backend_hint = webserver2;
                #return(pass);
        }
        else {
                return(synth(404,"Not in cache"));
        }

}

sub vcl_backend_response {
    # Happens after we have read the response headers from the backend.
    #
    # Here you clean the response headers, removing silly Set-Cookie headers
    # and other mistakes your backend does.
}

sub vcl_deliver {
    # Happens when we have all the pieces we need, and are about to send the
    # response to the client.
    #
    # You can do accounting or modifying the final object here
    # .
	if (obj.hits > 0) {
        	set resp.http.X-Cache = "Success! HIT from westos cache";
        }
        else {
        	set resp.http.X-Cache = "Fail! MISS from westos cache";
        }
        	return (deliver);
}