通过openresty限制访问频率（笔记）

shyai

local resolver = require "resty.dns.resolver"
local redis = require "resty.redis"

local user_agent = ngx.var.http_user_agent
local rip = ngx.var.remote_addr
local prip = resolver.arpa_str(rip)

local conn = redis:new()   
conn:set_timeout(1000)      
ok, err = conn:connect("10.0.10.111", 6379)  

if not ok then
    ngx.log(ngx.ERR, "failed to connect redis: ", err)
    conn:close()
end

local r, err = resolver:new{nameservers = {"114.114.114.114", "223.5.5.5"}, retrans = 5, timeout = 2000}

if not r then
    ngx.log(ngx.ERR, "failed to instantiate the resolver: ", err)
    return
end

--查询user-agent是否包含指定要限制字符
if ngx.re.match(user_agent, "yyy|xxx","ijo")then
  rds, err = conn:get(rip)
--查询redis里是否包含该ip，1：包含且是非法ip。0：包含且合法
  if rds == "1" then
    ngx.exit(502)
  elseif rds == ngx.null then
--redis值为null，dns查询并记录redis
    local answers, err = r:query(prip, {qtype = r.TYPE_PTR})
        if not answers then
      ngx.say("failed to query the DNS server: ", err)
    end
       
    if answers.errcode then
    ngx.say("server returned error code: ", answers.errcode,": ", answers.errstr)
    conn:set(rip,1)
    end

    for i, ans in ipairs(answers) do
      if ngx.re.match(ans.ptrdname, "(.*)xxx.com", "ijo")then
           conn:set(rip,0)
           ngx.say("OK!!")
        else
           ngx.say("Not OK!")
           conn:set(rip,1)
     end
   end
  end
end