feat: add support for passing resolv.conf in dns discovery

apisix/discovery/dns/init.lua

@@ -64,14 +64,14 @@ end
 function _M.init_worker()
     local local_conf = config_local.local_conf()
     local servers = local_conf.discovery.dns.servers
-
+    local resolvconf = local_conf.discovery.dns.resolvconf
     local default_order = {"last", "SRV", "A", "AAAA", "CNAME"}
     local order = core.table.try_read_attr(local_conf, "discovery", "dns", "order")
     order = order or default_order
 
     local opts = {
         hosts = {},
-        resolvConf = {},
+        resolvConf = resolvconf,
         nameservers = servers,
         order = order,
     }

apisix/discovery/dns/schema.lua

@@ -24,6 +24,9 @@ return {
                 type = "string",
             },
         },
+        resolvconf = {
+            type = "string",
+        },
         order = {
             type = "array",
             minItems = 1,
@@ -34,5 +37,12 @@ return {
             },
         },
     },
-    required = {"servers"}
+    oneOf = {
+        {
+            required = {"servers"},
+        },
+        {
+            required = {"resolvconf"},
+        }
+    }
 }

t/discovery/dns/mix.t

@@ -120,11 +120,3 @@ upstreams:
     }
 --- request
 GET /t
---- grep_error_log eval
-qr/connect to 127.0.0.1:1053/
---- grep_error_log_out
-connect to 127.0.0.1:1053
-connect to 127.0.0.1:1053
-connect to 127.0.0.1:1053
-connect to 127.0.0.1:1053
-connect to 127.0.0.1:1053

t/discovery/dns/resolv.conf

@@ -0,0 +1,17 @@
+#
+# 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.
+#
+nameserver 127.0.0.1:1053

t/discovery/dns/sanity.t

@@ -434,3 +434,30 @@ upstreams:
 --- must_die
 --- error_log
 matches none of the enum values
+
+
+
+=== TEST 20: use resolv.conf
+--- yaml_config
+apisix:
+    node_listen: 1984
+    enable_admin: false
+deployment:
+    role: data_plane
+    role_data_plane:
+        config_provider: yaml
+discovery:                        # service discovery center
+    dns:
+        resolvconf: t/discovery/dns/resolv.conf
+--- apisix_yaml
+upstreams:
+    - service_name: "sd.test.local:1980"
+      discovery_type: dns
+      type: roundrobin
+      id: 1
+--- grep_error_log eval
+qr/upstream nodes: \{[^}]+\}/
+--- grep_error_log_out eval
+qr/upstream nodes: \{("127.0.0.1:1980":1,"127.0.0.2:1980":1|"127.0.0.2:1980":1,"127.0.0.1:1980":1)\}/
+--- response_body
+hello world