通常情况下缓存是用来减少后端压力, 将压力尽可能的往前推, 减少后端压力,提高网站并发延时

1.缓存常见类型

服务端缓存

代理缓存, 获取服务端内容进行缓存

客户端浏览器缓存

Nginx代理缓存原理

2.缓存配置语法

proxy_cache配置语法

Syntax: proxy_cache zone | off;
Default: proxy_cache off;
Context: http, server, location

#1.缓存路径
Syntax: proxy_cache_path path [levels=levels]
[use_temp_path=on|off] keys_zOne=name:size [inactive=time]
[max_size=size] [manager_files=number] [manager_sleep=time][manager_threshold=time]
[loader_files=number] [loader_sleep=time] [loader_threshold=time] [purger=on|off]
[purger_files=number] [purger_sleep=time] [purger_threshold=time];
Default: —
Context: http

#2.缓存过期周期
Syntax: proxy_cache_valid [code ...] time;
Default: —
Context: http, server, location

#示例
proxy_cache_valid 200 302 10m;
proxy_cache_valid 404   1m;

#3.缓存的维度
Syntax: proxy_cache_key string;
Default:    proxy_cache_key $scheme$proxy_host$request_uri;
Context: http, server, location
#示例
proxy_cache_key "$host$request_uri $COOKIE_user";
proxy_cache_key $scheme$proxy_host$uri$is_args$args;

3.缓存配置实践

3.1.缓存准备

3.2.web节点准备

#建立相关目录
[root@web01 ~]# mkdir -p /soft/code{1..3}

#建立相关html文件
[root@web01 ~]# for i in {1..3};do echo Code1-Url$i > /soft/code1/url$i.html;done 
[root@web01 ~]# for i in {1..3};do echo Code2-Url$i > /soft/code2/url$i.html;done
[root@web01 ~]# for i in {1..3};do echo Code3-Url$i > /soft/code3/url$i.html;done

#配置Nginx
[root@web01 ~]# cat /etc/nginx/conf.d/web_node.conf 
server {
        listen 8081;
        root /soft/code1;
        index index.html;
}
server {
        listen 8082;
        root /soft/code2;
        index index.html;
}
server {
        listen 8083;
        root /soft/code3;
        index index.html;
}

#检查监听端口
[root@web01 ~]# netstat -lntp|grep 80
tcp        0      0 0.0.0.0:8081            0.0.0.0:*               LISTEN      50922/nginx: master 
tcp        0      0 0.0.0.0:8082            0.0.0.0:*               LISTEN      50922/nginx: master 
tcp        0      0 0.0.0.0:8083            0.0.0.0:*               LISTEN      50922/nginx: master

3.3.代理配置缓存

[root@lb01 ~]# mkdir /soft/cache
[root@lb01 ~]# cat /etc/nginx/conf.d/proxy_cache.conf
upstream cache {
    server 172.16.1.7:8081;
    server 172.16.1.7:8082;
    server 172.16.1.7:8083;
}

#proxy_cache存放缓存临时文件
#levels     按照两层目录分级
#keys_zone  开辟空间名, 10m:开辟空间大小, 1m可存放8000key
#max_size   控制最大大小, 超过后Nginx会启用淘汰规则
#inactive   60分钟没有被访问缓存会被清理
#use_temp_path  临时文件, 会影响性能, 建议关闭
proxy_cache_path /soft/cache levels=1:2 keys_zOne=code_cache:10m max_size=10g inactive=60m use_temp_path=off;

server {
        listen 80;
        server_name cache.bgx.com;

#proxy_cache        开启缓存
#proxy_cache_valid  状态码200|304的过期为12h, 其余状态码10分钟过期
#proxy_cache_key    缓存key
#add_header         增加头信息, 观察客户端respoce是否命中
#proxy_next_upstream 出现502-504或错误, 会跳过此台服务器访问下台
        location / {
                proxy_pass http://cache;
                proxy_cache code_cache;
                proxy_cache_valid 200 304 12h;
                proxy_cache_valid any 10m;
                add_header Nginx-Cache "$upstream_cache_status";
                proxy_next_upstream error timeout invalid_header http_500 http_502 http_503  http_504;
                include proxy_params;
        }
}

3.4.客户端测试

#第一次访问无法命中
[root@lb01 ~]# curl -s -I http://cache.bgx.com/url3.html|grep "Nginx-Cache"
Nginx-Cache: MISS

#第二次访问命中
[root@lb01 ~]# curl -s -I http://cache.bgx.com/url3.html|grep "Nginx-Cache"
Nginx-Cache: HIT

4.缓存如何清理

如何清理proxy_cache代理的缓存

4.1.使用rm删除已缓存数据

[root@lb01 ~]# rm -rf /soft/cache/*
[root@lb01 ~]# curl -s -I http://cache.bgx.com/url3.html|grep "Nginx-Cache"
Nginx-Cache: MISS

4.2.通过ngx_cache_purge扩展模块清理, 需要编译安装Nginx

#建立对应目录
[root@lb01 ~]# mkdir /soft/src
[root@lb01 ~]# cd /soft/src

#下载Nginx包
[root@lb01 ~]# wget http://nginx.org/download/nginx-1.12.2.tar.gz
[root@lb01 ~]# tar xf nginx-1.12.2.tar.gz

#下载ngx_cache_purge
[root@lb01 ~]# wget http://labs.frickle.com/files/ngx_cache_purge-2.3.tar.gz
[root@lb01 ~]# tar xf ngx_cache_purge-2.3.tar.gz

#编译Nginx

[root@lb01 ~]# cd nginx-1.12.2/ && ./configure \
--prefix=/server/nginx --add-module=../ngx_cache_purge-2.3 \
--with-http_stub_status_module --with-http_ssl_module
[root@lb01 ~]# make && make install

4.3.增加清理缓存的location，配置如下内容

[root@lb01 ~]# cat /etc/nginx/conf.d/proxy_cache.conf
upstream cache {
    server 172.16.1.7:8081;
    server 172.16.1.7:8082;
    server 172.16.1.7:8083;
}
proxy_cache_path /soft/cache levels=1:2 keys_zOne=code_cache:10m max_size=10g inactive=60m use_temp_path=off;

server {
    listen 80;
    server_name cache.bgx.com;

    location / {
        proxy_pass http://cache;
        proxy_cache code_cache;
        proxy_cache_valid 200 304 12h;
        proxy_cache_valid any 10m;
        add_header Nginx-Cache "$upstream_cache_status";
        proxy_next_upstream error timeout invalid_header http_500 http_502 http_503  http_504;
        include proxy_params;
        }
}
    location ~ /purge(/.*) {
        allow   127.0.0.1;
        allow   10.0.0.0/24;
        deny    all;
        proxy_cache_purge code_cache $host$1$is_args$args;
}

# 检测配置重新加载
[root@nginx conf.d]# /server/nginx/sbin/nginx -t
[root@nginx conf.d]# /server/nginx/sbin/nginx -s reload

4.4.使用浏览器访问建立缓存

4.5.通过访问purge/url地址，删除对应的缓存

4.6.再次刷新就会因为缓存内容已清理，而出现404错误

5.指定页面不缓存

如何配置指定部分页面不进行proxy_Cache缓存

[root@lb01 ~]# cat /etc/nginx/conf.d/proxy_cache.conf
upstream cache{
    server 172.16.1.7:8081;
    server 172.16.1.7:8082;
    server 172.16.1.7:8083;
}

proxy_cache_path /soft/cache levels=1:2 keys_zOne=code_cache:10m max_size=10g inactive=60m use_temp_path=off;

server {
    listen 80;
    server_name cache.bgx.com;
    #如果请求文件如下，则设定nocache为1
    if ($request_uri ~ ^/(url3|login|register|password)) {
        set $nocache 1;
    }

    location / {
        proxy_pass http://cache;
        proxy_cache code_cache;
        proxy_cache_valid 200 304 12h;
        proxy_cache_valid any 10m;
        proxy_cache_key $host$uri$is_args$args;
        proxy_no_cache $nocache $arg_nocache $arg_comment;  #不缓存变量为nocache
        proxy_no_cache $http_pargma $http_authorization;    #不缓存http参数以及http认证
        add_header Nginx-Cache "$upstream_cache_status";
        proxy_next_upstream error timeout invalid_header http_500 http_502 http_503  http_504;
        include proxy_params;
    }
}

#先清理所有缓存
[root@nginx ~]# rm -rf /soft/cache/*

#无论如何请求url3都无法命中
[root@nginx ~]# curl -s -I http://192.168.69.112/url3.html|grep "Nginx-Cache"    
Nginx-Cache: MISS
[root@nginx ~]# curl -s -I http://192.168.69.112/url3.html|grep "Nginx-Cache"
Nginx-Cache: MISS
[root@nginx ~]# curl -s -I http://192.168.69.112/url3.html|grep "Nginx-Cache"
Nginx-Cache: MISS

6.缓存日志记录

通过日志记录proxy_cache命中情况与对应url

6.1.修改nginx的log_format格式，增加"$upstream_cache_status"，该变量包含如下几种状态

MISS 未命中，请求被传送到后端
HIT 缓存命中，通过缓存返回数据
EXPIRED 缓存已经过期请求被传送到后端
UPDATING 正在更新缓存，将使用旧的应答
STALE 后端将得到过期的应答

[root@lb01 ~]# vim /etc/nginx/nginx.conf
http {
    log_format  main  '$http_user_agent' '$request_uri' '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"' '"$upstream_cache_status"';
}   

6.2.在server标签中添加对应的access日志

server {
    ...
    access_log /var/log/nginx/proxy_cache.log main;
    ...
}  

6.3.使用curl访问, 最后检查日志命令情况

[root@lb01 ~]# tail /var/log/nginx/proxy_cache.log
10.0.0.1 - - [19/Apr/2018:11:48:43 -0400] "HEAD /url3.html HTTP/1.1" 200 0 "-" "curl/7.29.0" "-""MISS"
10.0.0.1 - - [19/Apr/2018:11:48:45 -0400] "HEAD /url2.html HTTP/1.1" 200 0 "-" "curl/7.29.0" "-""HIT"
Nginx查看命中率