负载均衡

如果您在不同的实例中启动了服务，并且使用Nginx对这些服务做负载均衡，那么可能会发现如果直接使用Nginx Upstream进行代理会出现访问404。原因如下：由于WebCal需要根据用户请求Header中的Host进行路由到不同的实例（可以发现不同实例的URL地址域名不同，正常情况发起请求的域名地址会被设置到Header中的Host变量中）,当使用Nginx对多个后端服务进行代理时，用户前端请求的地址是Nginx所在服务器的地址，而在Nginx转发给WebCal的服务时无法重新设置Header中的Host变量为WebCal的域名导致无法正确访问。下面将介绍两种方法完成正确的代理： 1. 比较Trick的方法，适合需要代理的服务数量少的场景 2. 借助Lua脚本的方法，通用但是更加复杂

更Trick的方法

server {
  listen      8001 default_server;
  server_name a.example.com;
  location / {
    proxy_set_header Host a.cqa1.seetacloud.com:8443;
    proxy_pass       https://a.cqa1.seetacloud.com:8443;
  }
}

server {
  listen      8002 default_server;
  server_name b.example.com;
  location / {
    proxy_set_header Host b.cqa1.seetacloud.com:8443;
    proxy_pass       https://b.cqa1.seetacloud.com:8443;
  }
}

upstream main_balancer {
  server 127.0.0.1:8001;
  server 127.0.0.1:8002;
}

server {
  listen      80;
  server_name example.com;
  location / {
    proxy_pass http://main_balancer;
  }
}

借助Lua脚本的方法

Nginx配置

server {
  listen      8000 default_server;
  server_name web1.example.com;
  location / {
    set $proxy_pass_target "";
    set_by_lua_file $proxy_pass_target /usr/local/openresty/nginx/lua/xxxxxx.lua;
    if ($proxy_pass_target = ""){
        return 404;
    }
    proxy_set_header Host $proxy_pass_target;
    proxy_pass       https://$proxy_pass_target;
  }
}

Lua脚本

local servers = {
    ["0"] = "a.cqa1.seetacloud.com:8443",
    ["1"] = "b.cqa1.seetacloud.com:8443",
    ["2"] = "c.cqa1.seetacloud.com:8443",
}
local path = ngx.var.uri
local target = ""

if path == "/api/v1" then
    target = "api_v1.example.com"
elseif path == "/api/v2" then
    target = "api_v2.example.com"
else
    target = "default.api.example.com"
end

return target

更Trick的方法

server {
  listen      8001 default_server;
  server_name a.example.com;
  location / {
    proxy_set_header Host a.cqa1.seetacloud.com:8443;
    proxy_pass       https://a.cqa1.seetacloud.com:8443;
  }
}

server {
  listen      8002 default_server;
  server_name b.example.com;
  location / {
    proxy_set_header Host b.cqa1.seetacloud.com:8443;
    proxy_pass       https://b.cqa1.seetacloud.com:8443;
  }
}

upstream main_balancer {
  server 127.0.0.1:8001;
  server 127.0.0.1:8002;
}

server {
  listen      80;
  server_name example.com;
  location / {
    proxy_pass http://main_balancer;
  }
}

借助Lua脚本的方法

Nginx配置

server {
  listen      8000 default_server;
  server_name web1.example.com;
  location / {
    set $proxy_pass_target "";
    set_by_lua_file $proxy_pass_target /usr/local/openresty/nginx/lua/xxxxxx.lua;
    if ($proxy_pass_target = ""){
        return 404;
    }
    proxy_set_header Host $proxy_pass_target;
    proxy_pass       https://$proxy_pass_target;
  }
}

Lua脚本

local servers = {
    ["0"] = "a.cqa1.seetacloud.com:8443",
    ["1"] = "b.cqa1.seetacloud.com:8443",
    ["2"] = "c.cqa1.seetacloud.com:8443",
}
local path = ngx.var.uri
local target = ""

if path == "/api/v1" then
    target = "api_v1.example.com"
elseif path == "/api/v2" then
    target = "api_v2.example.com"
else
    target = "default.api.example.com"
end

return target