nginx proxy

nginx官方网站讲解proxy_pass时，只给了规则的说明，并没有给出具体的示例辅助理解。对于英语不太好的人，理解起来真的很头痛，只能通过测试来验证对英文意思的猜测。
nginx对proxy_pass的官方说明见http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_pass
其将proxy_pass的转发规则分为3类：

1. url中带path路径
2. url中不带path路径
3. nginx无法确认url的替换规则

如果域名后面带了“/”，则认为是url中带了path路径。比如：

1. proxy_pass http://127.0.0.1/
2. proxy_pass http://127.0.0.1/aaa
3. proxy_pass http://127.0.0.1/aaa/

nginx官网原文如下：

If the proxy_pass directive is specified with a URI, then when a request is passed to the server, the part of a normalized request URI matching the location is replaced by a URI specified in the directive:

location /name/ {
proxy_pass http://127.0.0.1/remote/;
}

个人理解如下：
使用proxy_pass配置的url去替换location指定的部分。如下图就是使用http://127.0.0.1/remote/去替换path中/name这一段

与第一点相反，proxy_pass指定url中只有域名，比如ttp://127.0.0.1

If proxy_pass is specified without a URI, the request URI is passed to the server in the same form as sent by a client when the original request is processed, or the full normalized request URI is passed when processing the changed URI:

location /some/path/ {
proxy_pass http://127.0.0.1;
}
个人理解如下：
转发url=proxy_pass配置的url+原始url中path部分

这种场景nginx又细分成3类

nginx官方要求配置proxy_pass时，不能带path路径。

When location is specified using a regular expression, and also inside named locations.
In these cases, proxy_pass should be specified without a URI.

比如

location /name/ {
rewrite /name/([^/]+) /users?name=$1 break;
proxy_pass http://127.0.0.1;
}

比如

location /name/ {
proxy_pass http://127.0.0.1$request_uri;
}