1 概念
The ngx_http_upstream_module is used to define groups of servers that can be referenced by the proxy_pass, fastcgi_pass, uwsgi_pass, scgi_pass, memcached_pass, and grpc_pass directives.
nginx反向代理做动静分离时，比如proxy_pass，后面只能写一个地址，如：http://127.0.0.1:8080，但有时需要多个动态组件以实现负载均衡，这时就可以把多个组件都写在一个upstream里，然后在proxy_pass餐后后面调unstream标签。
2 参数
upstream写在http标签里，一般在server上面，然后在server里引用。或者直接在一个vhost.cong里，写在server上面。
upstream jabphp {
server 10.102.22.12:9000 max_fails=20 fail_timeout=10 weight=5;
server 10.102.22.13:9000 max_fails=20 fail_timeout=10 weight=5;
server 10.102.22.14:9000 max_fails=20 fail_timeout=10 weight=5;
}
server {
listen 80;
server_name www.jab.com jab.com;
root /data/jab.com/;
#charset koi8-r;
access_log logs/jab.com.log main;
index index.php index.html;
location ~ .*\.php?$ {
fastcgi_pass jabphp;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
}
location / {...}
}