为什么要做web cache，我想大家最主要的是解决流量的压力。随着网站流量的提升，如果只是单台机器既处理静态文件，又处理动态脚本，显然效率很难上升，不能处理日益上涨的流量压力。与此同时某些网站的页面内容并不是经常变化，因此我们可以分两层架构来组织网站。前端web缓存+后端web服务器，可以参看这里配置nginx反向代理配置
前端web缓存有多重方式实现，原理就是队请求结果页面静态化并设置一个超时期限，缓存页面过期后，新请求到达时重新到后端web服务器获取内容更新；没有nginx前比较流行的方法是squid，但squid不能充分利用处理器的多核特性，越来越多的网站选用nginx来做前端的web缓存。
要想使用nginx的缓存功能要保证nginx添加了proxy模块。我们可以使用-V选项(大写的V，小写的v是看版本号的)来查看nginx的编译参数。我使用的是默认的参数编译的，如下所示：
root@SNDA-172-17-12-117:/usr/local/nginx# ./nginx -V
nginx version: nginx/1.2.3
built by gcc 4.4.3 (Ubuntu 4.4.3-4ubuntu5.1)
TLS SNI support enabled
configure arguments: --sbin-path=/usr/local/nginx/nginx --conf-path=/usr/local/nginx/nginx.conf --pid-path=/usr/local/nginx/nginx.pid --with-http_ssl_module --with-pcre=/usr/local/src/pcre-8.21 --with-zlib=/usr/local/src/zlib-1.2.7
nginx的所有模块必须在编译的时候添加，不能再运行的时候动态加载，默认的编译选项下包含的模块，如果你不是显示的用参数关闭它。
nginx默认安装的模块如下
| 模块名称 | 描述 | 版本 | 如何禁用 |
|---|---|---|---|
| Core | Control ports, locations, error pages, aliases, and other essentials. | --without-http | |
| Access | Allow/deny based on IP address. | --without-http_access_module | |
| Auth Basic | Basic HTTP authentication. | --without-http_auth_basic_module | |
| Auto Index | Generates automatic directory listings. | --without-http_autoindex_module | |
| Browser | Interpret "User-Agent" string. | 0.4.3 | --without-http_browser_module |
| Charset | Recode web pages. | --without-http_charset_module | |
| Empty GIF | Serve a 1x1 image from memory. | 0.3.10 | --without-http_empty_gif_module |
| FastCGI | FastCGI Support. | --without-http_fastcgi_module | |
| Geo | Set config variables using key/value pairs of IP addresses. | 0.1.17 | --without-http_geo_module |
| Gzip | Gzip responses. | --without-http_gzip_module | |
| Headers | Set arbitrary HTTP response headers. | ||
| Index | Controls which files are to be used as index. | ||
| Limit Requests | Limit frequency of connections from a client. | 0.7.20 | --without-http_limit_req_module |
| Limit Zone | Limit simultaneous connections from a client. Deprecated in 1.1.8, use Limit Conn Instead. | 0.5.6 | --without-http_limit_zone_module |
| Limit Conn | Limit concurrent connections based on a variable. | --without-http_limit_conn_module | |
| Log | Customize access logs. | ||
| Map | Set config variables using arbitrary key/value pairs. | 0.3.16 | --without-http_map_module |
| Memcached | Memcached support. | --without-http_memcached_module | |
| Proxy | Proxy to upstream servers. | --without-http_proxy_module | |
| Referer | Filter requests based on Referer header. |
--without-http_referer_module | |
| Rewrite | Request rewriting using regular expressions. | --without-http_rewrite_module | |
| SCGI | SCGI protocol support. | 0.8.42 | --without-http_scgi_module |
| Split Clients | Splits clients based on some conditions | 0.8.37 | --without-http_split_clients_module |
| SSI | Server-side includes. | --without-http_ssi_module | |
| Upstream | For load-balancing. | --without-http_upstream_ip_hash_module (ip_hash directive only) | |
| User ID | Issue identifying cookies. | --without-http_userid_module | |
| uWSGI | uWSGI protocol support. | 0.8.40 | --without-http_uwsgi_module |
| X-Accel | X-Sendfile-like module. |
proxy模块中常用的指令时proxy_pass和proxy_cache.
nginx的web缓存功能的主要是由proxy_cache、fastcgi_cache指令集和相关指令集完成，proxy_cache指令负责反向代理缓存后端服务器的静态内容，fastcgi_cache主要用来处理FastCGI动态进程缓存(这里我不是很清楚这两个指令的区别，好像功能上都差不多，尤其后面这句话的意思，是我翻译过来的)。
确认proxy模块安装好后，下面对nginx的配置文件进行设置，重点部分如标红字体所示。
这是我的nginx.conf配置文件。
user www-data; worker_processes 1; #error_log logs/error.log; #error_log logs/error.log notice; #error_log logs/error.log info; #pid logs/nginx.pid; events { worker_connections 1024; } http { include mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] "$request" ' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for" "$host"'; #access_log logs/access.log main; sendfile on; #tcp_nopush on; #keepalive_timeout 0; keepalive_timeout 65; #Compression Settings gzip on; gzip_http_version 1.0; gzip_comp_level 2; gzip_proxied any; gzip_min_length 1100; gzip_buffers 16 8k; gzip_types text/plain text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript; # Some version of IE 6 don't handle compression well on some mime-types, # so just disable for them gzip_disable "MSIE [1-6].(?!.*SV1)"; # Set a vary header so downstream proxies don't send cached gzipped # content to IE6 gzip_vary on; #end gzip #cache begin proxy_buffering on; proxy_cache_valid any 10m; proxy_cache_path /data/cache levels=1:2 keys_zone=my-cache:8m max_size=1000m inactive=600m; proxy_temp_path /data/temp; proxy_buffer_size 4k; proxy_buffers 100 8k; #cache end ## Basic reverse proxy server ## ## Apache (vm02) backend for www.example.com ## upstream apachephp { server www.quancha.cn:8080; #Apache1 } ## Start www.quancha.cn ## server { listen 80; server_name *.quancha.cn; access_log logs/quancha.access.log main; error_log logs/quancha.error.log; root html; index index.html index.htm index.php; ## send request back to apache1 ## location / { proxy_pass http://apachephp; proxy_cache my-cache; proxy_cache_valid 200; #Proxy Settings proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_next_upstream error timeout invalid_header http_500 http_502 http_503 http_504; proxy_max_temp_file_size 0; proxy_connect_timeout 90; proxy_send_timeout 90; proxy_read_timeout 90; proxy_buffer_size 4k; proxy_buffers 4 32k; proxy_busy_buffers_size 64k; proxy_temp_file_write_size 64k; ##End Proxy Settings } } ## End www.quancha.cn ## }
配置文件中以proxy_开头的指令我们大都可以字面意思得到理解。请务必注意一点proxy_cache_path和proxy_temp_path设置的目录需要在同一分区，因为它们之间是硬链接的关系。
最后启动nginx，来迎接着激动人心的时刻吧。我已经迫不及待了。如果文章哪里有问题或者你遇到了什么麻烦，可以留言让我知道。