[nginx]proxy_pass&rewrite知识点

While passing request nginx replaces URI part which corresponds to location with one indicated in proxy_pass directive. But there are two exceptions from this rule when it is not possible to determine what to replace:

if the location is given by regular expression;
if inside proxied location URI is changed by rewrite directive, and this configuration will be used to process request (break):
location  /name/ {
  rewrite      /name/([^/] +)  /users?name=$  break;
  proxy_pass   http://127.0.0.1;
}
For these cases of URI it is transferred without the mapping.
注意：
两种情况下不进行代理转换。
1.location 标段使用正则表达式
2.执行代理动作的location段内使用了rewrite指令对location URI进行了修改，并且使用rewrite后的配置发出请求（break）。

A special case is using variables in the proxy_pass statement: The requested URL is not used and you are fully responsible to construct the target URL yourself.

This means, the following is not what you want for rewriting into a zope virtual host monster, as it will proxy always to the same URL (within one server specification):

另一种特例是在proxy_pass语句中使用变量：请求的url并没有被使用，你必须自己构造目标url

location / {
  proxy_pass   http://127.0.0.1:8080/VirtualHostBase/https/$server_name:443/some/path/VirtualHostRoot;
}
Instead use a combination of rewrite and proxy_pass:上面的语句要写成下面的：

location / {
  rewrite ^(.*)$ /VirtualHostBase/https/$server_name:/some/path/VirtualHostRoot$ break;
  proxy_pass   http://127.0.0.1:8080;
}

rewrite的permanent和redirect重写后的url会在url栏显示，在数据包的层面，添加了location http header

这块东西还是有不少不清楚的地方，继续研究。