Nginx 的配置是启动时一次性加载到内存中的，在实际的使用中，对 Nginx 服务器上游服务器组中节点的添加或移除仍需要重启或热加载 Nginx 进程。在 Nginx 的商业版本中，提供了 ngx_http_api_module 模块，可以通过 API 动态添加或移除上游服务器组中的节点。

对于 Nginx 开源版本，通过 Nginx 的扩展版 OpenResty 及 Lua 脚本也可以实现上游服务器组中节点的动态操作，这里只使用 OpenResty 的 lua-upstream-nginx-module 模块简单演示节点的上下线状态动态修改的操作。该模块提供了 set_peer_down 指令，该指令可以对 upstream 的节点实现上下线的控制。

由于该指令只支持 worker 级别的操作，为使得 Nginx 的所有 worker 都生效，此处通过编写 Lua 脚本与 lua-resty-upstream-healthcheck 模块做了简单的集成，利用 lua-resty-upstream-healthcheck 模块的共享内存机制将节点状态同步给其他工作进程，实现对 upstream 的节点状态的控制。

首先在 OpenResty 的 lualib 目录下创建公用函数文件 api_func.lua，lualib/api_func.lua 内容如下：

local _M = { _VERSION = '1.0' }

local cjson = require "cjson"

local upstream = require "ngx.upstream"

local get_servers = upstream.get_servers

local get_primary_peers = upstream.get_primary_peers

local set_peer_down = upstream.set_peer_down

# 分割字符串为table

local function split( str,reps )

local resultStrList = {}

string.gsub(str,"[^"..reps.."]+",function ( w )

table.insert(resultStrList,w)

end)

return resultStrList

end

# 获取server列表

local function get_args_srv( args )

if not args["server"] then

ngx.say("failed to get post args: ", err)

return nil

else

if type(args["server"]) ~= "table" then

server_list=split(args["server"],",")

else

server_list=args["server"]

end

end

return server_list

end

# 获取节点在upstream中的顺序

local function get_peer_id(ups,server_name)

local srvs = get_servers(ups)

for i, srv in ipairs(srvs) do

-- ngx.print(srv["name"])

if srv["name"] == server_name then

target_srv = srv

target_srv["id"] = i-1

break

end

end

return target_srv["id"]

end

# 获取节点共享内存key

local function gen_peer_key(prefix, u, is_backup, id)

if is_backup then

return prefix .. u .. ":b" .. id

end

return prefix .. u .. ":p" .. id

end

# 设置节点状态

local function set_peer_down_globally(ups, is_backup, id, value,zone_define)

local u = ups

local dict = zone_define

local ok, err = set_peer_down(u, is_backup, id, value)

if not ok then

ngx.say(cjson.encode({code = "E002", msg = "failed to set peer down", data = err}))

end

local key = gen_peer_key("d:", u, is_backup, id)

local ok, err = dict:set(key, value)

if not ok then

ngx.say(cjson.encode({code = "E003", msg = "failed to set peer down state", data = err}))

end

end

# 获取指定upstream的节点列表

function _M.list_server(ups)

local srvs, err = get_servers(ups)

ngx.say(cjson.encode(srvs))

end

# 设置节点状态

function _M.set_server(ups,args,status,backup,zone_define)

local server_list = get_args_srv(args)

if server_list == nil then

ngx.say(cjson.encode({code = "E001", msg = "no args",data = server_list}))

return nil

end

for _, s in pairs(server_list) do

local peer_id = get_peer_id(ups,s)

if status then

local key = gen_peer_key("nok:", ups, backup, peer_id)

local ok, err = zone_define:set(key, 1)

set_peer_down_globally(ups, backup, peer_id, true,zone_define)

else

local key = gen_peer_key("ok:", ups, backup, peer_id)

local ok, err = zone_define:set(key, 0)

set_peer_down_globally(ups, backup, peer_id, nil,zone_define)

end

end

ngx.say(cjson.encode({code = "D002", msg = "set peer is success",data = server_list}))

end

return _M

Nginx 配置文件 status.conf 的内容如下：

# 关闭socket错误日志

lua_socket_log_errors off;

# 设置共享内存名称及大小

lua_shared_dict _healthcheck_zone 10m;

init_worker_by_lua_block {

local hc = require "resty.upstream.healthcheck"

# 设置需要健康监测的upstream

local ups = {"foo.com","sslback"}

# 遍历ups，绑定健康监测策略

for k, v in pairs(ups) do

local ok, err = hc.spawn_checker{

shm = "_healthcheck_zone", # 绑定lua_shared_dict定义的共享内存

upstream = v, # 绑定upstream指令域

type = "http",

http_req = "GET / HTTP/1.0\r\nHost: foo.com\r\n\r\n",

# 用以检测的raw格式http请求

interval = 2000, # 每2s检测一次

timeout = 1000, # 检测请求超时时间为1s

fall = 3, # 连续失败3次，被检测节点被置为DOWN状态

rise = 2, # 连续成功2次，被检测节点被置为UP状态

# 当健康检测请求返回的响应码为200或302时，被认

# 为检测通过

valid_statuses = {200, 302},

concurrency = 10, # 健康检测请求的并发数为10

}

if not ok then

ngx.log(ngx.ERR, "failed to spawn health checker: ", err)

return

end

end

}

upstream foo.com {

server 192.168.2.145:8080;

server 192.168.2.109:8080;

server 127.0.0.1:12356 backup;

}

upstream sslback {

server 192.168.2.145:443;

server 192.168.2.159:443;

}

server {

listen 18080;

access_log off;

error_log off;

# 健康检测状态页

location = /healthcheck {

access_log off;

allow 127.0.0.1;

allow 192.168.2.0/24;

allow 192.168.101.0/24;

deny all;

default_type text/plain;

content_by_lua_block {

local hc = require "resty.upstream.healthcheck"

ngx.say("Nginx Worker PID: ", ngx.worker.pid())

ngx.print(hc.status_page())

}

}

location = /ups_api {

default_type application/json;

content_by_lua '

# 获取URL参数

local ups = ngx.req.get_uri_args()["ups"]

local act = ngx.req.get_uri_args()["act"]

if act == nil or ups == nil then

ngx.say("usage: /ups_api?ups={name}&act=[down,up,list]")

return

end

# 引用api_func.lua脚本

local api_fun = require "api_func"

# 绑定共享内存_healthcheck_zone

local zone_define=ngx.shared["_healthcheck_zone"]

if act == "list" then

# 获取指定upstream的节点列表

api_fun.list_server(ups)

else

ngx.req.read_body()

local args, err = ngx.req.get_post_args()

if act == "up" then

# 节点状态将设置为UP

api_fun.set_server(ups,args,false,false,zone_define)

end

if act == "down" then

# 节点状态将设置为DOWN

api_fun.set_server(ups,args,true,false,zone_define)

end

end

';

}

}

操作命令如下：

# 查看upstream foo.com的服务器列表

curl “http://127.0.0.1:18080/ups_api?act=list&ups=foo.com”

# 将192.168.2.145:8080这个节点设置为DOWN状态

curl -X POST -d “server=192.168.2.145:8080” “http://127.0.0.1:18080/ups_api?act= down&ups=foo.com”

# 将192.168.2.145:8080这个节点设置为UP状态

curl -X POST -d “server=192.168.2.145:8080” “http://127.0.0.1:18080/ups_api?act= up&ups=foo.com”