feat: add support for passing resolv.conf in dns discovery (apache#9770)

Author: Revolyssup

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 resolv_conf = local_conf.discovery.dns.resolv_conf
     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 = resolv_conf,
         nameservers = servers,
         order = order,
     }

apisix/discovery/dns/schema.lua

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

ci/common.sh

@@ -140,6 +140,9 @@ set_coredns() {
     pushd t/coredns || exit 1
     ../../build-cache/coredns -dns.port=1053 &
     popd || exit 1
+
+    touch build-cache/test_resolve.conf
+    echo "nameserver 127.0.0.1:1053" > build-cache/test_resolve.conf
 }
 
 GRPC_SERVER_EXAMPLE_VER=20210819

conf/config-default.yaml

@@ -280,6 +280,7 @@ nginx_config:                     # Config for render the template to generate n
 #  dns:
 #    servers:
 #      - "127.0.0.1:8600"         # Replace with the address of your DNS server.
+#    resolv_conf: /etc/resolv.conf # Replace with the path to the local DNS resolv config. Configure either "servers" or "resolv_conf".
 #    order:                       # Resolve DNS records this order.
 #      - last                     # Try the latest successful type for a hostname.
 #      - SRV

t/discovery/dns/mix.t

@@ -128,3 +128,4 @@ 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/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:
+        resolv_conf: build-cache/test_resolve.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