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--[[
Copyright (C) 2018 ZTE, Inc. and others. All rights reserved. (ZTE)
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
--]]
local _M = {}
_M._VERSION = '1.0.0'
local shcache = require("vendor.shcache")
local msbConf = require('conf.msbinit')
local resolver = require "resty.dns.resolver"
local str_util = require('lib.utils.str_util')
local dns_cache = ngx.shared.dns_cache
local dns_servers = msbConf.dns.servers
local dns_cache_positive_ttl = msbConf.dns.cache_positive_ttl or 60
local dns_cache_negative_ttl = msbConf.dns.cache_negative_ttl or 2
local dns_cache_actualize_ttl = msbConf.dns.cache_actualize_ttl or 120
local str_split = str_util.split
local nameservers = nil
ngx.log(ngx.WARN, "environment variable UPSTREAM_DNS_SERVERS:",dns_servers)
local ok,res = pcall(function() return str_split(dns_servers,",") end)
if not ok then
ngx.log(ngx.WARN, "failed to parse the DNS Servers from the environment variable UPSTREAM_DNS_SERVERS"," Error:"..res)
else
nameservers = res
end
local function query(domain)
-- closure to perform external lookup to redis
local dns_query_from_server = function ()
local r, err = resolver:new{
nameservers = nameservers,
retrans = 5, -- 5 retransmissions on receive timeout
timeout = 2000, -- 2 sec
}
if not r then
ngx.log(ngx.ERR, "failed to instantiate the resolver:",err)
return nil,"failed to instantiate the resolver:"..err
end
--local answers, err = r:query("wygtest.service.openpalette")
local answers, err = r:query(domain)
if not answers then
ngx.log(ngx.ERR, "failed to query the DNS server:",err)
return nil,"failed to query the DNS server:"..err
end
if answers.errcode then
ngx.log(ngx.ERR, "server returned error code: ", answers.errcode,
": ", answers.errstr)
return nil,"server returned error code: "..answers.errcode..
": ".. answers.errstr
end
for i, ans in ipairs(answers) do
if r.TYPE_A==ans.type and r.CLASS_IN==ans.class then
return ans.address
end
end
return nil,"dns servers return answers,but no server is TYPE_A and CLASS_IN"
end
local dns_cache_table = shcache:new(
dns_cache,
{ external_lookup = dns_query_from_server,
--encode = cmsgpack.pack,
--encode = cjson_safe.encode,
--decode = cmsgpack.unpack
--decode = cjson_safe.decode
},
{ positive_ttl = dns_cache_positive_ttl, -- default cache good data for 60s
negative_ttl = dns_cache_negative_ttl, -- default cache failed lookup for 1s
actualize_ttl = dns_cache_actualize_ttl,
name = 'dns_cache' -- "named" cache, useful for debug / report
}
)
local server, from_cache = dns_cache_table:load(domain)
return server
end
_M.query = query
return _M
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