1 files changed, 99 insertions, 0 deletions
diff --git a/openresty-ext/src/assembly/resources/openresty/nginx/luaext/lib/utils/dns_util.lua b/openresty-ext/src/assembly/resources/openresty/nginx/luaext/lib/utils/dns_util.lua
new file mode 100644
index 0000000..c2ac7b1
--- /dev/null
+++ b/openresty-ext/src/assembly/resources/openresty/nginx/luaext/lib/utils/dns_util.lua
@@ -0,0 +1,99 @@
+--[[
+
+    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