[dns] refactor search list

gateway/src/resty/resolver.lua

@@ -9,6 +9,7 @@ local find = string.find
 local insert = table.insert
 local concat = table.concat
 local io_type = io.type
+local table_new = require("table.new")
 
 require('resty.core.regex') -- to allow use of ngx.re.match in the init phase
 
@@ -285,15 +286,35 @@ local function valid_answers(answers)
   return answers and not answers.errcode and #answers > 0 and (not answers.addresses or #answers.addresses > 0)
 end
 
+-- construct search list from resolv options: search
+-- @param search table of search domain
+-- @param qname the name to query for
+-- @return table with search names
+local function search_list(search, qname)
+  -- FQDN
+  if sub(qname, -1) == "." then
+    return {qname}
+  end
+
+  local names = table_new(#search +1, 0)
+  for i=1, #search do
+    names[i] = qname .. "." .. search[i]
+  end
+  return names
+end
+
 local function search_dns(self, qname, stale)
 
   local search = self.search
   local dns = self.dns
   local options = self.options
   local cache = self.cache
+  local answers, err
+  local names = search_list(search, qname)
 
-  local function get_answer(query)
-    local answers, err
+  -- resolve all `names` and return the first valid answers
+  for _, query in ipairs(names) do
+    ngx.log(ngx.DEBUG, 'resolver query: ', qname, ' query: ', query)
     answers, err = cache:get(query, stale)
     if valid_answers(answers) then
       return answers, err
@@ -304,23 +325,6 @@ local function search_dns(self, qname, stale)
       cache:save(answers)
       return answers, err
     end
-    return nil, err
-  end
-
-  if sub(qname, -1) == "." then
-    local query = sub(qname, 1 ,-2)
-    ngx.log(ngx.DEBUG, 'resolver query: ', qname, ' query: ', query)
-    return get_answer(query)
-  end
-
-  local answer, err
-  for i=1, #search do
-    local query = qname .. '.' .. search[i]
-    ngx.log(ngx.DEBUG, 'resolver query: ', qname, ' search: ', search[i], ' query: ', query)
-    answer, err = get_answer(query)
-    if answer then
-      return answer, err
-    end
   end
 
   return nil, err
@@ -342,6 +346,12 @@ local function resolve_upstream(qname)
   return peers
 end
 
+-- Queries the DNS for this qname. If nothing is in the cache, a
+-- synchoronous queryis performed. If the cache is stale, first query is going
+-- to refresh the query while all others use stale cache data.
+-- @param qname the name to look for
+-- @param stale if true return stale data
+-- @return dns `answers + nil`, or `nil + error
 function _M.lookup(self, qname, stale)
   local cache = self.cache
 

spec/resty/resolver_spec.lua

@@ -1,5 +1,6 @@
 local resty_resolver = require 'resty.resolver'
 local resolver_cache = require 'resty.resolver.cache'
+local string_byte = string.byte
 
 describe('resty.resolver', function()
 
@@ -131,6 +132,11 @@ describe('resty.resolver', function()
     before_each(function()
       local dns = {
         query = spy.new(function(_, name)
+          -- FQDN, drop the last '.' as the answer does not contain it
+
+          if string_byte(name, -1) == string_byte(".") then
+            name = name:sub(1, -2)
+          end
           return {
             { name = name , address = '127.0.0.1' }
           }