nginx 如何处理请求

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How nginx processes a request - nginx 如何处理请求

https://nginx.org/en/docs/http/request_processing.html

基于名称的虚拟服务器 - Name-based virtual servers

nginx first decides which server should process the request. Let’s start with a simple configuration where all three virtual servers listen on port *:80:

​ nginx 首先决定哪个 server 应该处理请求。让我们从一个简单的配置开始，其中所有三个虚拟服务器都在端口 *:80 上监听：

server {
 listen      80;
 server_name example.org www.example.org;
 ...
}

server {
 listen      80;
 server_name example.net www.example.net;
 ...
}

server {
 listen      80;
 server_name example.com www.example.com;
 ...
}

In this configuration nginx tests only the request’s header field “Host” to determine which server the request should be routed to. If its value does not match any server name, or the request does not contain this header field at all, then nginx will route the request to the default server for this port. In the configuration above, the default server is the first one — which is nginx’s standard default behaviour. It can also be set explicitly which server should be default, with the default_server parameter in the listen directive:

​ 在此配置中，nginx 仅测试请求的标头字段 “Host” 以确定应将请求路由到哪个服务器。如果其值与任何服务器名称不匹配，或者请求根本不包含此标头字段，则 nginx 将请求路由到该端口的默认服务器。在上述配置中，默认服务器是第一个服务器，这是 nginx 的标准默认行为。也可以通过 listen 指令中的 default_server 参数明确设置哪个服务器应该是默认服务器：

server {
 listen      80 default_server;
 server_name example.net www.example.net;
 ...
}

The default_server parameter has been available since version 0.8.21. In earlier versions the default parameter should be used instead.

​ default_server 参数自版本 0.8.21 可用。在早期版本中，应使用 default 参数。

Note that the default server is a property of the listen port and not of the server name. More about this later.

​ 请注意，默认服务器是侦听端口的属性，而不是服务器名称的属性。稍后会详细介绍。

如何防止处理未定义服务器名称的请求 - How to prevent processing requests with undefined server names

If requests without the “Host” header field should not be allowed, a server that just drops the requests can be defined:

​ 如果不允许没有 “Host” 标头字段的请求，可以定义一个仅丢弃请求的服务器：

server {
 listen      80;
 server_name "";
 return      444;
}

Here, the server name is set to an empty string that will match requests without the “Host” header field, and a special nginx’s non-standard code 444 is returned that closes the connection.

​ 在这里，服务器名称设置为空字符串，将与不带 “Host” 标头字段的请求匹配，并返回特殊的非标准 nginx 代码 444，从而关闭连接。

Since version 0.8.48, this is the default setting for the server name, so the server_name "" can be omitted. In earlier versions, the machine’s hostname was used as a default server name.

​ 自版本 0.8.48 起，这是服务器名称的默认设置，因此可以省略 server_name ""。在早期版本中，机器的 主机名 用作默认服务器名称。

混合基于名称和基于 IP 的虚拟服务器 - Mixed name-based and IP-based virtual servers

Let’s look at a more complex configuration where some virtual servers listen on different addresses:

​ 让我们看一个更复杂的配置，其中一些虚拟服务器在不同的地址上监听：

server {
 listen      192.168.1.1:80;
 server_name example.org www.example.org;
 ...
}

server {
 listen      192.168.1.1:80;
 server_name example.net www.example.net;
 ...
}

server {
 listen      192.168.1.2:80;
 server_name example.com www.example.com;
 ...
}

In this configuration, nginx first tests the IP address and port of the request against the listen directives of the server blocks. It then tests the “Host” header field of the request against the server_name entries of the server blocks that matched the IP address and port. If the server name is not found, the request will be processed by the default server. For example, a request for www.example.com received on the 192.168.1.1:80 port will be handled by the default server of the 192.168.1.1:80 port, i.e., by the first server, since there is no www.example.com defined for this port.

​ 在此配置中，nginx 首先将请求的 IP 地址和端口与 server 块的 listen 指令进行测试。然后，它将请求的 “Host” 标头字段与匹配 IP 地址和端口的 server 块的 server_name 条目进行测试。如果找不到服务器名称，则请求将由默认服务器处理。例如，在 192.168.1.1:80 端口上接收到的 www.example.com 请求将由 192.168.1.1:80 端口的默认服务器处理，即第一个服务器，因为在此端口上没有为 www.example.com 定义。

As already stated, a default server is a property of the listen port, and different default servers may be defined for different ports:

​ 如前所述，默认服务器是侦听端口的属性，可以为不同的端口定义不同的默认服务器：

server {
 listen      192.168.1.1:80;
 server_name example.org www.example.org;
 ...
}

server {
 listen      192.168.1.1:80 default_server;
 server_name example.net www.example.net;
 ...
}

server {
 listen      192.168.1.2:80 default_server;
 server_name example.com www.example.com;
 ...
}

一个简单的 PHP 网站配置 - A simple PHP site configuration

Now let’s look at how nginx chooses a location to process a request for a typical, simple PHP site:

​ 现在，让我们看看 nginx 如何选择处理请求的 location，以处理典型的简单 PHP 网站请求：

server {
 listen      80;
 server_name example.org www.example.org;
 root        /data/www;

 location / {
     index   index.html index.php;
 }

 location ~* \.(gif|jpg|png)$ {
     expires 30d;
 }

 location ~ \.php$ {
     fastcgi_pass  localhost:9000;
     fastcgi_param SCRIPT_FILENAME
                   $document_root$fastcgi_script_name;
     include       fastcgi_params;
 }
}

nginx first searches for the most specific prefix location given by literal strings regardless of the listed order. In the configuration above the only prefix location is “/” and since it matches any request it will be used as a last resort. Then nginx checks locations given by regular expression in the order listed in the configuration file. The first matching expression stops the search and nginx will use this location. If no regular expression matches a request, then nginx uses the most specific prefix location found earlier.

​ nginx 首先搜索最特定的前缀位置，这些位置由字面字符串给出，无论其在列表中的顺序如何。在上面的配置中，唯一的前缀位置是 “/”，由于它匹配任何请求，它将作为最后的选择被使用。然后，nginx 按照配置文件中列出的顺序检查由正则表达式给出的位置。第一个匹配的表达式会停止搜索，nginx 将使用此位置。如果没有正则表达式匹配请求，则 nginx 使用稍早找到的最特定的前缀位置。

Note that locations of all types test only a URI part of request line without arguments. This is done because arguments in the query string may be given in several ways, for example:

​ 请注意，所有类型的位置测试仅测试请求行的 URI 部分，而不包括参数。这样做是因为查询字符串中的参数可以以多种方式给出，例如：

/index.php?user=john&page=1
/index.php?page=1&user=john

Besides, anyone may request anything in the query string:

​ 此外，任何人都可以在查询字符串中请求任何内容：

/index.php?page=1&something+else&user=john

Now let’s look at how requests would be processed in the configuration above:

​ 现在，让我们看看上述配置中请求如何被处理：

  • A request “/logo.gif” is matched by the prefix location “/” first and then by the regular expression “\.(gif|jpg|png)$”, therefore, it is handled by the latter location. Using the directive “root /data/www” the request is mapped to the file /data/www/logo.gif, and the file is sent to the client.
  • 请求 “/logo.gif” 首先与前缀位置 “/” 匹配，然后与正则表达式 “\.(gif|jpg|png)$” 匹配，因此，它由后者位置处理。使用指令 “root /data/www”，请求将映射到文件 /data/www/logo.gif，然后将文件发送给客户端。
  • A request “/index.php” is also matched by the prefix location “/” first and then by the regular expression “\.(php)$”. Therefore, it is handled by the latter location and the request is passed to a FastCGI server listening on localhost:9000. The fastcgi_param directive sets the FastCGI parameter SCRIPT_FILENAME to “/data/www/index.php”, and the FastCGI server executes the file. The variable $document_root is equal to the value of the root directive and the variable $fastcgi_script_name is equal to the request URI, i.e. “/index.php”.
  • 请求 “/index.php” 也首先与前缀位置 “/” 匹配，然后与正则表达式 “\.(php)$” 匹配。因此，它由后者位置处理，并将请求传递给在 localhost:9000 上侦听的 FastCGI 服务器。fastcgi_param 指令将 FastCGI 参数 SCRIPT_FILENAME 设置为 “/data/www/index.php”，FastCGI 服务器执行该文件。变量 $document_root 等于 root 指令的值，变量 $fastcgi_script_name 等于请求 URI，即 “/index.php”。
  • A request “/about.html” is matched by the prefix location “/” only, therefore, it is handled in this location. Using the directive “root /data/www” the request is mapped to the file /data/www/about.html, and the file is sent to the client.
  • 请求 “/about.html” 仅与前缀位置 “/” 匹配，因此，在此位置处理。使用指令 “root /data/www”，请求将映射到文件 /data/www/about.html，然后将文件发送给客户端。
  • Handling a request “/” is more complex. It is matched by the prefix location “/” only, therefore, it is handled by this location. Then the index directive tests for the existence of index files according to its parameters and the “root /data/www” directive. If the file /data/www/index.html does not exist, and the file /data/www/index.php exists, then the directive does an internal redirect to “/index.php”, and nginx searches the locations again as if the request had been sent by a client. As we saw before, the redirected request will eventually be handled by the FastCGI server.
  • 处理请求 “/” 更为复杂。它仅与前缀位置 “/” 匹配，因此，由此位置处理。然后，index 指令根据其参数和 “root /data/www” 指令的值测试索引文件的存在。如果文件 /data/www/index.html 不存在，但文件 /data/www/index.php 存在，则该指令将进行内部重定向到 “/index.php”，nginx 将再次像客户端发送请求一样搜索位置。正如我们之前所看到的，重定向的请求最终将由 FastCGI 服务器处理。

written by Igor Sysoev edited by Brian Mercer

最后修改 August 17, 2023: 更新 (1829eb9)