# 2.5.Node + Nginx

* Why Nginx?
  * 負載均衡
    * 負載均衡的目的是為了單個節點過大, 造成Web服務回應速度過慢, 嚴重導致服務癱瘓, 無法正常提供服務
  * Nginx
    * Nginx是一個負載均衡服務器(Load Balancer), 由Nginx前置頂住壓力, 後面多個node server完成業務支撑。
    * 實現負載均衡常用的Web服務器有Nginx、HAProxy、LVS、Apache等
  * Nginx的內置負載策略 (Load Balance)
    * 透過upstream模組來實現, 共有三種方式:
      * 1.輪詢 (Round Robin): Nginx以事先定好的順序, 讓輪流server們輪流處理requset, 也是預設的分配方式
      * 2.最少連結 (Least Connections): Request將會給當下連線數量最少的server
      * 3.Ip-Hash/Sticky Sessions:綁定處理請求的服務器。第一次請求時, 根據客户端的IP算出一个HASH值, 將請求分配到集群中的某一台服務器上. 後面該客户端的所有請求, 都將透過HASH算法找到之前處理這台客户端請求的服务器, 然後將請求交给它来處理.
      * 4.權重(Weight):

        ```
        http {
           upstream node_server_pool {
              server 192.168.0.100:8080 weight=2;  # 2/6次
              server 192.168.0.101:8080 weight=3;  # 3/6次
              server 192.168.0.102:8080 weight=1;  # 1/6次
            }
          server{
            listen       80;
             server_name localhost;
            location /
            {
              proxy_pass http://node_server_pool;
            }
        }
        ```
* Install Nginx on Ubuntu 14.04 LTS

  ```
  sudo apt-get update
  sudo apt-get install nginx
  ```
* config balance loader
  * example

    ```
    sudo nano /etc/nginx/nginx.conf
    worker_processes  1;
      events {
        worker_connections  1024;
      }
      http {
         upstream node_server_pool {
           server localhost:3001 max_fails=1;
           server localhost:3000 max_fails=1;
          }
      server{
        listen       80;
        server_name localhost;
        location /
        {
          proxy_pass http://node_server_pool;
         }
      }
    }
    ```
* config Nginx cahe server
  * config

    ```
      # Expire rules for static content

      # cache.appcache, your document html and data
      location ~* \.(?:manifest|appcache|html?|xml|json)$ {
        expires -1;
        # access_log logs/static.log; # I don't usually include a static log
      }

      # Feed
      location ~* \.(?:rss|atom)$ {
          expires 1h;
        add_header Cache-Control "public";
      }

    # Media: images, icons, video, audio, HTC
    location ~* \.(?:jpg|jpeg|gif|png|ico|cur|gz|svg|svgz|mp4|ogg|ogv|webm|htc)$ {
        expires 1M;
      access_log off;
      add_header Cache-Control "public";
    }

    # CSS and Javascript
    location ~* \.(?:css|js)$ {
      expires 1y;
      access_log off;
      add_header Cache-Control "public";
    }
    ```
  * check if cache control enable
  * reference
* Reference:
  * <http://blog.csdn.net/xyang81/article/details/51702900>