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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"] thenngx.say("failed to get post args: ", err)return nilelseif type(args["server"]) ~= "table" thenserver_list=split(args["server"],",")elseserver_list=args["server"]endendreturn 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 thentarget_srv = srvtarget_srv["id"] = i-1breakendendreturn 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 thenreturn prefix .. u .. ":b" .. idendreturn 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 = upslocal dict = zone_definelocal ok, err = set_peer_down(u, is_backup, id, value)if not ok thenngx.say(cjson.encode({code = "E002", msg = "failed to set peer down", data = err}))endlocal key = gen_peer_key("d:", u, is_backup, id)local ok, err = dict:set(key, value)if not ok thenngx.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 thenngx.say(cjson.encode({code = "E001", msg = "no args",data = server_list}))return nilendfor _, s in pairs(server_list) dolocal peer_id = get_peer_id(ups,s)if status thenlocal 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)elselocal 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)endendngx.say(cjson.encode({code = "D002", msg = "set peer is success",data = server_list}))
endreturn _MNginx 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upstreamlocal ups = {"foo.com","sslback"}# 遍历ups，绑定健康监测策略for k, v in pairs(ups) dolocal 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1sfall = 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 thenngx.log(ngx.ERR, "failed to spawn health checker: ", err)returnendend
}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 thenngx.say("usage: /ups_api?ups={name}&act=[down,up,list]")returnend# 引用api_func.lua脚本local api_fun = require "api_func"# 绑定共享内存_healthcheck_zonelocal 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)elsengx.req.read_body()local args, err = ngx.req.get_post_args()if act == "up" then# 节点状态将设置为UPapi_fun.set_server(ups,args,false,false,zone_define)endif act == "down" then# 节点状态将设置为DOWNapi_fun.set_server(ups,args,true,false,zone_define)endend';}
}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"
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