Support the combination of nginx variables and text value for annotation upstream-hash-by.

rootfs/etc/nginx/lua/balancer/chash.lua

@@ -1,14 +1,21 @@
 local balancer_resty = require("balancer.resty")
 local resty_chash = require("resty.chash")
 local util = require("util")
+local ngx_log = ngx.log
+local ngx_ERR = ngx.ERR
 
 local _M = balancer_resty:new({ factory = resty_chash, name = "chash" })
 
 function _M.new(self, backend)
   local nodes = util.get_nodes(backend.endpoints)
+  local complex_val, err = util.parse_complex_value(backend["upstreamHashByConfig"]["upstream-hash-by"])
+  if err ~= nil then
+    ngx_log(ngx_ERR, "could not parse the value of the upstream-hash-by: ", err)
+  end
+
   local o = {
     instance = self.factory:new(nodes),
-    hash_by = backend["upstreamHashByConfig"]["upstream-hash-by"],
+    hash_by = complex_val,
     traffic_shaping_policy = backend.trafficShapingPolicy,
     alternative_backends = backend.alternativeBackends,
   }
@@ -18,7 +25,7 @@ function _M.new(self, backend)
 end
 
 function _M.balance(self)
-  local key = util.lua_ngx_var(self.hash_by)
+  local key = util.generate_var_value(self.hash_by)
   return self.instance:find(key)
 end