处理HTTP请求的11个阶段
如下图：
| 序号 | 阶段 | 指令 | 备注 |
| 1 | POST_READ | realip | 获取客户端真实IP |
| 2 | SERVER_REWRITE | rewrite | |
| 3 | FIND_CONFIG | ||
| 4 | REWRITE | rewrite | |
| 5 | POST_REWRITE | ||
| 6 | PRE_ACCESS | limit_conn, limit_req | |
| 7 | ACCESS | auth_basic, access, auth_request | auth_basic可以做访问限制 |
| 8 | POST_ACCESS | ||
| 9 | PRE_CONTENT | try_files | |
| 10 | CONTENT | index, autoindex, concat | |
| 11 | LOG | access_log | access_log记录请求日志 |
