add_header 指令技巧

官方的介绍：

Adds the specified field to a response header provided that the response code equals 200, 201 (1.3.10), 204, 206, 301, 302, 303, 304, 307 (1.1.16, 1.0.13), or 308 (1.13.0). The value can contain variables.

There could be several add_header directives. These directives are inherited from the previous level if and only if there are no add_header directives defined on the current level.

If the always parameter is specified (1.7.5), the header field will be added regardless of the response code.

意思也就是说话在响应状态码成功时，add_header 指令才生效，并且当前《作用域》下没有 add_header 指令时，会向上层继承。

在使用过程中难免会遇到上级指令被覆盖的情况，如：

server {
    add_header x-name nginx;

    location / {
        root /path;
    }

    location /static/ {
        add_header x-name2 nginx2;
    }
}

当匹配到 / 时，由于 location / 中没有 add_header 指令，所以会继承 server 中的 x-name ，而当匹配到 /static/ 时，由于内容已经有 add_header 指令，则上层的 x-name 不会被继承，导致只会输出 x-name2 。

使用 include 语法

因为项目中的应用往往配置会有很多，我们可以把具体的功能拆分成独立的配置文件，使用 include 引用进来，如：

• inc/no-cache.conf - 无缓存
• inc/cache-max.conf - 缓存最大
• inc/sts.conf - STS
• inc/xss.conf - XSS 安全过滤
• inc/php.conf - PHP FastCGI
• ...

这样就可以按需引用了，如：

location / {
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/no-cache.conf;
}

# png,jpg 转 webp
location ~* \.(jpg|png|meibanfawojiuxiangchangdianyirangquanzhongdadian)$ {
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/cache-max.conf;

    if ($cookie_webp = '1') {
        rewrite ^/(.*)$ /$1.webp last;
    }
}
location ~* \.webp$ {
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/cache-max.conf;
    try_files $uri $uri/ @webp;
}
location @webp {
    content_by_lua_file 'lua/webp.lua';
}

# http-concat + max cache
location /style/js/ {
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/cache-max.conf;
    concat on;
    concat_types application/javascript;
    concat_max_files 30;
    default_type application/javascript;
}
location /style/css/ {
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/cache-max.conf;
    concat on;
    concat_types text/css;
    concat_max_files 30;
    default_type text/css;
}

# 时效性高的接口
location ~* ^/((so\/(.+))||ajax)\.php$ {
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/php.conf;
    add_header cache-control 'private, max-age=0, no-cache';
}

# 其实所有的 php
location ~* \.php$ {
    set $skip_cache 0;
    if ($request_method = POST) {
        set $skip_cache 1;
    }
    if ($arg_nocache = "1") {
        set $skip_cache 1;
    }

    fastcgi_cache_key $scheme$request_method$host$request_uri;
    fastcgi_cache_use_stale
        error
        timeout
        invalid_header
        updating
        http_500
        http_503;
    fastcgi_cache_bypass $skip_cache;
    fastcgi_no_cache $skip_cache;
    fastcgi_cache_valid 200 5m;
    fastcgi_cache_valid any 1m;
    fastcgi_cache m_xiaoshuo_php_cache;

    add_header x-php-cache-status $upstream_cache_status;
    include inc/sts.conf;
    include inc/security.conf;
    include vhost/xiaoshuo.io/cache-small.conf;
    include vhost/xiaoshuo.io/php.conf;
}