| -- |
| -- Licensed to the Apache Software Foundation (ASF) under one or more |
| -- contributor license agreements. See the NOTICE file distributed with |
| -- this work for additional information regarding copyright ownership. |
| -- The ASF licenses this file to You 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 require = require |
| local log = require("apisix.core.log") |
| local json = require("apisix.core.json") |
| local table = require("apisix.core.table") |
| local insert_tab = table.insert |
| local math_random = math.random |
| local package_loaded = package.loaded |
| local ipairs = ipairs |
| local setmetatable = setmetatable |
| |
| |
| local _M = { |
| RETURN_RANDOM = 1, |
| RETURN_ALL = 2, |
| } |
| |
| |
| local function gcd(a, b) |
| if b == 0 then |
| return a |
| end |
| |
| return gcd(b, a % b) |
| end |
| |
| |
| local function resolve_srv(client, answers) |
| if #answers == 0 then |
| return nil, "empty SRV record" |
| end |
| |
| local resolved_answers = {} |
| local answer_to_count = {} |
| for _, answer in ipairs(answers) do |
| if answer.type ~= client.TYPE_SRV then |
| return nil, "mess SRV with other record" |
| end |
| |
| local resolved, err = client.resolve(answer.target) |
| if not resolved then |
| local msg = "failed to resolve SRV record " .. answer.target .. ": " .. err |
| return nil, msg |
| end |
| |
| log.info("dns resolve SRV ", answer.target, ", result: ", |
| json.delay_encode(resolved)) |
| |
| local weight = answer.weight |
| if weight == 0 then |
| weight = 1 |
| end |
| |
| local count = #resolved |
| answer_to_count[answer] = count |
| -- one target may have multiple resolved results |
| for _, res in ipairs(resolved) do |
| local copy = table.deepcopy(res) |
| copy.weight = weight / count |
| copy.port = answer.port |
| copy.priority = answer.priority |
| insert_tab(resolved_answers, copy) |
| end |
| end |
| |
| -- find the least common multiple of the counts |
| local lcm = answer_to_count[answers[1]] |
| for i = 2, #answers do |
| local count = answer_to_count[answers[i]] |
| lcm = count * lcm / gcd(count, lcm) |
| end |
| -- fix the weight as the weight should be integer |
| for _, res in ipairs(resolved_answers) do |
| res.weight = res.weight * lcm |
| end |
| |
| return resolved_answers |
| end |
| |
| |
| function _M.resolve(self, domain, selector) |
| local client = self.client |
| |
| -- this function will dereference the CNAME records |
| local answers, err = client.resolve(domain) |
| if not answers then |
| return nil, "failed to query the DNS server: " .. err |
| end |
| |
| if answers.errcode then |
| return nil, "server returned error code: " .. answers.errcode |
| .. ": " .. answers.errstr |
| end |
| |
| if selector == _M.RETURN_ALL then |
| log.info("dns resolve ", domain, ", result: ", json.delay_encode(answers)) |
| for _, answer in ipairs(answers) do |
| if answer.type == client.TYPE_SRV then |
| return resolve_srv(client, answers) |
| end |
| end |
| return table.deepcopy(answers) |
| end |
| |
| local idx = math_random(1, #answers) |
| local answer = answers[idx] |
| local dns_type = answer.type |
| if dns_type == client.TYPE_A or dns_type == client.TYPE_AAAA then |
| log.info("dns resolve ", domain, ", result: ", json.delay_encode(answer)) |
| return table.deepcopy(answer) |
| end |
| |
| return nil, "unsupport DNS answer" |
| end |
| |
| |
| function _M.new(opts) |
| opts.ipv6 = true |
| opts.timeout = 2000 -- 2 sec |
| opts.retrans = 5 -- 5 retransmissions on receive timeout |
| |
| -- make sure each client has its separate room |
| package_loaded["resty.dns.client"] = nil |
| local dns_client_mod = require("resty.dns.client") |
| |
| local ok, err = dns_client_mod.init(opts) |
| if not ok then |
| return nil, "failed to init the dns client: " .. err |
| end |
| |
| return setmetatable({client = dns_client_mod}, {__index = _M}) |
| end |
| |
| |
| return _M |