diff --git a/kong/router/atc.lua b/kong/router/atc.lua
index 492f361de9b0..8d2776386131 100644
--- a/kong/router/atc.lua
+++ b/kong/router/atc.lua
@@ -35,8 +35,6 @@ local ngx_ERR       = ngx.ERR
 local check_select_params  = utils.check_select_params
 local get_service_info     = utils.get_service_info
 local route_match_stat     = utils.route_match_stat
-local get_cache_key        = fields.get_cache_key
-local fill_atc_context      = fields.fill_atc_context
 
 
 local DEFAULT_MATCH_LRUCACHE_SIZE = utils.DEFAULT_MATCH_LRUCACHE_SIZE
@@ -57,35 +55,6 @@ local CACHED_SCHEMA
 local HTTP_SCHEMA
 local STREAM_SCHEMA
 do
-  local HTTP_FIELDS = {
-
-    ["String"] = {"net.protocol", "tls.sni",
-                  "http.method", "http.host",
-                  "http.path",
-                  "http.path.segments.*",
-                  "http.headers.*",
-                  "http.queries.*",
-                 },
-
-    ["Int"]    = {"net.src.port", "net.dst.port",
-                 },
-
-    ["IpAddr"] = {"net.src.ip", "net.dst.ip",
-                 },
-  }
-
-  local STREAM_FIELDS = {
-
-    ["String"] = {"net.protocol", "tls.sni",
-                 },
-
-    ["Int"]    = {"net.src.port", "net.dst.port",
-                 },
-
-    ["IpAddr"] = {"net.src.ip", "net.dst.ip",
-                 },
-  }
-
   local function generate_schema(fields)
     local s = schema.new()
 
@@ -99,8 +68,8 @@ do
   end
 
   -- used by validation
-  HTTP_SCHEMA   = generate_schema(HTTP_FIELDS)
-  STREAM_SCHEMA = generate_schema(STREAM_FIELDS)
+  HTTP_SCHEMA   = generate_schema(fields.HTTP_FIELDS)
+  STREAM_SCHEMA = generate_schema(fields.STREAM_FIELDS)
 
   -- used by running router
   CACHED_SCHEMA = is_http and HTTP_SCHEMA or STREAM_SCHEMA
@@ -227,14 +196,12 @@ local function new_from_scratch(routes, get_exp_and_priority)
     yield(true, phase)
   end
 
-  local fields = inst:get_fields()
-
   return setmetatable({
       context = context.new(CACHED_SCHEMA),
+      fields = fields.new(inst:get_fields()),
       router = inst,
       routes = routes_t,
       services = services_t,
-      fields = fields,
       updated_at = new_updated_at,
       rebuilding = false,
     }, _MT)
@@ -318,9 +285,7 @@ local function new_from_previous(routes, get_exp_and_priority, old_router)
     yield(true, phase)
   end
 
-  local fields = inst:get_fields()
-
-  old_router.fields = fields
+  old_router.fields = fields.new(inst:get_fields())
   old_router.updated_at = new_updated_at
   old_router.rebuilding = false
 
@@ -436,7 +401,7 @@ function _M:matching(params)
 
   self.context:reset()
 
-  local c, err = fill_atc_context(self.context, self.fields, params)
+  local c, err = self.fields:fill_atc_context(self.context, params)
 
   if not c then
     return nil, err
@@ -503,6 +468,8 @@ end
 
 
 function _M:exec(ctx)
+  local fields = self.fields
+
   local req_uri = ctx and ctx.request_uri or var.request_uri
   local req_host = var.http_host
 
@@ -520,7 +487,7 @@ function _M:exec(ctx)
   CACHE_PARAMS.uri  = req_uri
   CACHE_PARAMS.host = req_host
 
-  local cache_key = get_cache_key(self.fields, CACHE_PARAMS)
+  local cache_key = fields:get_cache_key(CACHE_PARAMS)
 
   -- cache lookup
 
@@ -580,7 +547,7 @@ function _M:matching(params)
 
   self.context:reset()
 
-  local c, err = fill_atc_context(self.context, self.fields, params)
+  local c, err = self.fields:fill_atc_context(self.context, params)
   if not c then
     return nil, err
   end
@@ -633,6 +600,8 @@ end
 
 
 function _M:exec(ctx)
+  local fields = self.fields
+
   -- cache key calculation
 
   if not CACHE_PARAMS then
@@ -642,7 +611,7 @@ function _M:exec(ctx)
 
   CACHE_PARAMS:clear()
 
-  local cache_key = get_cache_key(self.fields, CACHE_PARAMS, ctx)
+  local cache_key = fields:get_cache_key(CACHE_PARAMS, ctx)
 
   -- cache lookup
 
@@ -681,7 +650,7 @@ function _M:exec(ctx)
 
     -- preserve_host logic, modify cache result
     if match_t.route.preserve_host then
-      match_t.upstream_host = fields.get_value("tls.sni", CACHE_PARAMS)
+      match_t.upstream_host = fields:get_value("tls.sni", CACHE_PARAMS)
     end
   end
 
diff --git a/kong/router/fields.lua b/kong/router/fields.lua
index 21dfc244f14a..3608459f556f 100644
--- a/kong/router/fields.lua
+++ b/kong/router/fields.lua
@@ -5,6 +5,7 @@ local type = type
 local ipairs = ipairs
 local assert = assert
 local tonumber = tonumber
+local setmetatable = setmetatable
 local tb_sort = table.sort
 local tb_concat = table.concat
 local replace_dashes_lower = require("kong.tools.string").replace_dashes_lower
@@ -22,6 +23,37 @@ local HTTP_HEADERS_PREFIX = "http.headers."
 local HTTP_QUERIES_PREFIX = "http.queries."
 
 
+local HTTP_FIELDS = {
+
+  ["String"] = {"net.protocol", "tls.sni",
+                "http.method", "http.host",
+                "http.path",
+                "http.path.segments.*",
+                "http.headers.*",
+                "http.queries.*",
+               },
+
+  ["Int"]    = {"net.src.port", "net.dst.port",
+               },
+
+  ["IpAddr"] = {"net.src.ip", "net.dst.ip",
+               },
+}
+
+
+local STREAM_FIELDS = {
+
+  ["String"] = {"net.protocol", "tls.sni",
+               },
+
+  ["Int"]    = {"net.src.port", "net.dst.port",
+               },
+
+  ["IpAddr"] = {"net.src.ip", "net.dst.ip",
+               },
+}
+
+
 local FIELDS_FUNCS = {
     -- http.*
 
@@ -164,6 +196,10 @@ else  -- stream
 end -- is_http
 
 
+-- stream subsystem need not to generate func
+local get_field_accessor = function(funcs, field) end
+
+
 if is_http then
 
   local fmt = string.format
@@ -197,30 +233,54 @@ if is_http then
   end
 
 
-  setmetatable(FIELDS_FUNCS, {
-  __index = function(_, field)
+  get_field_accessor = function(funcs, field)
+    local f = funcs[field]
+    if f then
+      return f
+    end
+
     local prefix = field:sub(1, PREFIX_LEN)
 
+    -- generate for http.headers.*
+
     if prefix == HTTP_HEADERS_PREFIX then
-      return function(params)
+      local name = field:sub(PREFIX_LEN + 1)
+
+      f = function(params)
         if not params.headers then
           params.headers = get_http_params(get_headers, "headers", "lua_max_req_headers")
         end
 
-        return params.headers[field:sub(PREFIX_LEN + 1)]
-      end
+        return params.headers[name]
+      end -- f
 
-    elseif prefix == HTTP_QUERIES_PREFIX then
-      return function(params)
+      funcs[field] = f
+      return f
+    end -- if prefix == HTTP_HEADERS_PREFIX
+
+    -- generate for http.queries.*
+
+    if prefix == HTTP_QUERIES_PREFIX then
+      local name = field:sub(PREFIX_LEN + 1)
+
+      f = function(params)
         if not params.queries then
           params.queries = get_http_params(get_uri_args, "queries", "lua_max_uri_args")
         end
 
-        return params.queries[field:sub(PREFIX_LEN + 1)]
-      end
+        return params.queries[name]
+      end -- f
+
+      funcs[field] = f
+      return f
+    end -- if prefix == HTTP_QUERIES_PREFIX
 
-    elseif field:sub(1, HTTP_SEGMENTS_PREFIX_LEN) == HTTP_SEGMENTS_PREFIX then
-      return function(params)
+    -- generate for http.path.segments.*
+
+    if field:sub(1, HTTP_SEGMENTS_PREFIX_LEN) == HTTP_SEGMENTS_PREFIX then
+      local range = field:sub(HTTP_SEGMENTS_PREFIX_LEN + 1)
+
+      f = function(params)
         if not params.segments then
           HTTP_SEGMENTS_REG_CTX.pos = 2 -- reset ctx, skip first '/'
           params.segments = re_split(params.uri, "/", "jo", HTTP_SEGMENTS_REG_CTX)
@@ -228,7 +288,6 @@ if is_http then
 
         local segments = params.segments
 
-        local range = field:sub(HTTP_SEGMENTS_PREFIX_LEN + 1)
         local value = segments[range]
 
         if value then
@@ -276,31 +335,47 @@ if is_http then
         segments[range] = value
 
         return value
-      end
+      end -- f
 
-    end -- if prefix
+      funcs[field] = f
+      return f
+    end -- if field:sub(1, HTTP_SEGMENTS_PREFIX_LEN)
 
     -- others return nil
   end
-  })
 
 end -- is_http
 
 
-local function get_value(field, params, ctx)
-  local func = FIELDS_FUNCS[field]
+local _M = {}
+local _MT = { __index = _M, }
+
 
-  if not func then  -- unknown field
-    error("unknown router matching schema field: " .. field)
-  end -- if func
+_M.HTTP_FIELDS = HTTP_FIELDS
+_M.STREAM_FIELDS = STREAM_FIELDS
+
+
+function _M.new(fields)
+  return setmetatable({
+      fields = fields,
+      funcs = {},
+    }, _MT)
+end
+
+
+function _M:get_value(field, params, ctx)
+  local func = FIELDS_FUNCS[field] or
+               get_field_accessor(self.funcs, field)
+
+  assert(func, "unknown router matching schema field: " .. field)
 
   return func(params, ctx)
 end
 
 
-local function fields_visitor(fields, params, ctx, cb)
-  for _, field in ipairs(fields) do
-    local value = get_value(field, params, ctx)
+function _M:fields_visitor(params, ctx, cb)
+  for _, field in ipairs(self.fields) do
+    local value = self:get_value(field, params, ctx)
 
     local res, err = cb(field, value)
     if not res then
@@ -316,11 +391,11 @@ end
 local str_buf = buffer.new(64)
 
 
-local function get_cache_key(fields, params, ctx)
+function _M:get_cache_key(params, ctx)
   str_buf:reset()
 
   local res =
-  fields_visitor(fields, params, ctx, function(field, value)
+  self:fields_visitor(params, ctx, function(field, value)
 
     -- these fields were not in cache key
     if field == "net.protocol" then
@@ -361,11 +436,11 @@ local function get_cache_key(fields, params, ctx)
 end
 
 
-local function fill_atc_context(context, fields, params)
+function _M:fill_atc_context(context, params)
   local c = context
 
   local res, err =
-  fields_visitor(fields, params, nil, function(field, value)
+  self:fields_visitor(params, nil, function(field, value)
 
     local prefix = field:sub(1, PREFIX_LEN)
 
@@ -404,7 +479,7 @@ local function fill_atc_context(context, fields, params)
 end
 
 
-local function _set_ngx(mock_ngx)
+function _M._set_ngx(mock_ngx)
   if mock_ngx.var then
     var = mock_ngx.var
   end
@@ -425,11 +500,4 @@ local function _set_ngx(mock_ngx)
 end
 
 
-return {
-  get_value = get_value,
-
-  get_cache_key = get_cache_key,
-  fill_atc_context = fill_atc_context,
-
-  _set_ngx = _set_ngx,
-}
+return _M