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Nginx负载均衡 -Nginx动态更新upstream

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”

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