help request: how to use dns discovery in serverless-pre-function

[haochencheng]

Description

i want use domain to findout host and port from dns server . i do like this ,it wrong

{
  "disable": false,
  "functions": [
    "return function(conf, ctx)    local core = require 'apisix.core';  core.log.warn(\"ctx\",ctx);  local discovery = require(\"apisix.discovery.init\").discovery; core.log.warn(\"discovery\",core.json.encode(discovery)); local discovery_type = require(\"apisix.core.config_local\").local_conf().discovery;core.log.warn(\"discovery_type\",core.json.encod(discovery_type)); end;"
  ],
  "phase": "before_proxy"
}

it's ok ,but i don't have port .

   local resolvers = {''};
    core.utils.set_resolver(resolvers);
    local domain = 'xxx';
    local ip_info, err = core.utils.dns_parse(domain,core.dns.client.RETURN_ALL);
    if not ip_info then\n
        core.log.warn(ngx.EMERG,'failed to parse domain: '..domain..', error: '..json.encode(err));
    else\n 
        core.log.warn(ngx.EMERG,'parse domain success: ',domain,'===ip_info:', core.json.encode(ip_info),', error: ',err);    
    end;

Environment

• APISIX version 2.15.0 (run apisix version):
• Operating system (run uname -a): 3.10.0-957.27.2.el7.x86_64 change: added doc of how to load plugin. #1 SMP Mon Jul 29 17:46:05 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
• OpenResty / Nginx version (run openresty -V or nginx -V): openresty/1.21.4.1
• etcd version, if relevant (run curl http://127.0.0.1:9090/v1/server_info): 3.4.0
• APISIX Dashboard version, if relevant:
• Plugin runner version, for issues related to plugin runners:
• LuaRocks version, for installation issues (run luarocks --version): 2.3.0

[tokers]

@haochencheng Please show us what you want. The port from SRV record?

[tzssangglass]

Since this question is not a specific issue, it is transformed into a discussion.

[haochencheng]

yes, i want use service_name got host and port from dns discovery. btw, i use consul as service registry center.

[tokers]

Have you tried to fetch the SRV records directly? e.g. via dig utility.

[haochencheng]

Could i get a dns_client in customer plugin ? Is my action correct?
i want know can I get the internal components of apisix like discovery in the plugin
like this:

local ipairs = ipairs
local core   = require("apisix.core")
local dns_client   = require("apisix.discovery.dns.init").dns_client
local http   = require("resty.http")
local roundrobin  = require("resty.roundrobin")

function _M.access(conf, ctx)
  local dns_client   = require("apisix.discovery.dns.init").dns_client
      core.log.info("service_name========",conf.service_name);
      local nodes = dns_client.nodes(conf.service_name)
      local picker = roundrobin:new(nodes)
      local server, err = picker:find()
      if not server then
          return nil, err
      end
end


return _M

now it's a nil value .

Or I can only parse and not reuse the components of apisix.

[haochencheng]

Have you tried to fetch the SRV records directly? e.g. via dig utility.

here is fetch SRV directly.

dig @127.0.0.1 -p8600 poseidon-auth.service.dc1.consul SRV

; <<>> DiG 9.10.6 <<>> @127.0.0.1 -p8600 poseidon-auth.service.dc1.consul SRV
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48283
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 3
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;poseidon-auth.service.dc1.consul. IN SRV

;; ANSWER SECTION:
poseidon-auth.service.dc1.consul. 0 IN SRV 1 1 10099 c0a80162.addr.dc1.consul.

;; ADDITIONAL SECTION:
c0a80162.addr.dc1.consul. 0 IN A 192.168.1.98
macdeMacBook-Pro-2.local.node.dc1.consul. 0 IN TXT "consul-network-segment="

;; Query time: 0 msec
;; SERVER: 127.0.0.1#8600(127.0.0.1)
;; WHEN: Tue Aug 23 17:00:47 CST 2022
;; MSG SIZE rcvd: 187

this is core dns client resolve_srv log :
2022/08/22 10:07:02 [info] 232#232: *7132759 [lua] client.lua:60: resolve(): dns resolve SRV 0a0a0096.addr.dc1.consul, result: {"1":{"type":1,"section":3,"ttl":0,"address":"10.10.0.150","name":"0a0a0096.addr.dc1.consul","class":1},"ttl":0,"expired":false,"expire":1661162822.22,"touch":1661162822.22},

[tzssangglass]

You can see an example of using consul as a DNS server here: #6694 (comment)

[haochencheng]

thanks a lot

[haochencheng]

Thank you all . i found a way to solving my problem , I used the wrong api before .

--
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-- 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
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-- 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 ipairs = ipairs
local core   = require("apisix.core")
local http   = require("resty.http")
local roundrobin  = require("resty.roundrobin")
local config_local = require("apisix.core.config_local")
local discovery = require("apisix.discovery.dns.init")

local schema = {
    type = "object",
    properties = {
        service_name = {type = "string",description = "the service name for client to request the authorization service",default="xxx.service.consul"},
        uri = {type="string",description = "the uri for client to request the authorization service",default = "/"},
        ssl_verify = {
            type = "boolean",
            default = true,
        },
        request_method = {
            type = "string",
            default = "GET",
            enum = {"GET", "POST","PUT","DELETE"},
            description = "the method for client to request the authorization service"
        },
        request_headers = {
            type = "array",
            default = {},
            items = {type = "string"},
            description = "client request header that will be sent to the authorization service"
        },
        upstream_headers = {
            type = "array",
            default = {},
            items = {type = "string"},
            description = "authorization response header that will be sent to the upstream"
        },
        client_headers = {
            type = "array",
            default = {},
            items = {type = "string"},
            description = "authorization response header that will be sent to"
                           .. "the client when authorizing failed"
        },
        timeout = {
            type = "integer",
            minimum = 1,
            maximum = 60000,
            default = 1000,
            description = "timeout in milliseconds",
        },
        keepalive = {type = "boolean", default = true},
        keepalive_timeout = {type = "integer", minimum = 1000, default = 60000},
        keepalive_pool = {type = "integer", minimum = 1, default = 5},
    }
}

local dns_resolvers
local current_inited_resolvers


local _M = {
    version = 0.1,
    priority = 2001,
    name = "xx-auth",
    schema = schema,
}


function _M.check_schema(conf)
    return core.schema.check(schema, conf)
end

local function dns_parse(domain)
    if dns_resolvers ~= current_inited_resolvers then
        discovery.init_worker()
        current_inited_resolvers = dns_resolvers
    end

    return discovery.nodes(domain)
end

local function set_resolver(resolvers)
    dns_resolvers = resolvers
end

function _M.access(conf, ctx)
  
    core.log.warn("ctx=========",core.json.encode(ctx, true))
    -- discover
    local service_name = conf.service_name
    core.log.info("service_name========",service_name);

    local local_conf = config_local.local_conf()
    local resolvers = local_conf.discovery.dns.servers
    core.log.info("resolvers========",core.json.encode(resolvers))

    -- core.utils.set_resolver(resolvers)
    -- local records, err = core.utils.dns_parse(service_name, core.dns_client.RETURN_ALL)

    set_resolver(resolvers)
    local nodes, err = dns_parse(service_name)
    if not nodes then
        return nil, err
    end
    core.log.info('nodes==========',core.json.encode(nodes))
   
end


return _M