1. Nginx概述

   Nginx是一个高性能的http服务器和反向代理服务器，也是一个IMAP/POP3/SMTP代理服务器。
   Ngnix开源、免费、高性能、可靠，配置简单、资源消耗小、拥有丰富的扩展模块。
   不像传统的服务器，Nginx不依赖于线程去处理requests，而是使用更易于伸缩的事件驱动（异步的）体系结构。This architecture uses small, but more importantly, predictable amounts of memory under load.即使你不需要处理成千上万的并发请求，你依然可以使用Nginx的高性能与较小的内存消耗的特点。Nginx的伸缩性是全方位的，从最小的VPS到大规模集群。
   
   Nginx拥有一个master进程和多个worker进程，
   master进程：读取和设置配置文件，以及管理worker进程
   worker进程：实际处理request
   
   Nginx通过基于事件的模型和操作系统依赖机制来实现在worker进程中高效的派发requests。（nginx employs event-based model and OS-dependent mechanisms to efficiently distribute requests among worker processes.）
   
   Nginx以及它的模块的工作方式有配置文件决定。

2. Nginx配置文件

   配置文件的结构：
   Nginx的组成模块由配置文件中申明的配置项控制。配置项分为简单配置项和块配置项。一个简单配置项有name以及用空格分离的parameters以及用来结尾的“;”组成。一个块配置项拥有和简单配置项类似的结构，不过不同的是它是以用（{和}）包围的一集合的附加命令取代“;”结尾。如果一个块配置项在它的（{、}）拥有其他的配置项，它被称作一个上下文。
   不放在任何contexts中的配置项被认为处于main context中，因此 events 和 http 配置项处于main context中，server处于http上下文中，location处于server上下文中。
   余下的以#开头的部分被认为是注释。
   

   nginx consists of modules which are controlled by directives specified in the configuration file. Directives are divided into simple directives and block directives. A simple directive consists of the name and parameters separated by spaces and ends with a semicolon (;). A block directive has the same structure as a simple directive, but instead of the semicolon it ends with a set of additional instructions surrounded by braces ({ and }). If a block directive can have other directives inside braces, it is called a context (examples: events, http, server, and location).

   Directives placed in the configuration file outside of any contexts are considered to be in the main context. The events and http directives reside in the main context, server in http, and location in server.

   The rest of a line after the # sign is considered a comment.

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nginx学习笔记