use roundrobin from lua-resty-balancer library and refactor balancer.lua

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

@@ -1,48 +0,0 @@
-local resty_chash = require("resty.chash")
-local util = require("util")
-local string_sub = string.sub
-
-local _M = {}
-local instances = {}
-
--- given an Nginx variable i.e $request_uri
--- it returns value of ngx.var[request_uri]
-local function get_lua_ngx_var(ngx_var)
-  local var_name = string_sub(ngx_var, 2)
-  return ngx.var[var_name]
-end
-
-function _M.balance(backend)
-  local instance = instances[backend.name]
-  if not instance then
-    return nil
-  end
-
-  local key = get_lua_ngx_var(backend["upstream-hash-by"])
-  local endpoint_string = instance:find(key)
-
-  local address, port = util.split_pair(endpoint_string, ":")
-  return { address = address, port = port }
-end
-
-function _M.reinit(backend)
-  local instance = instances[backend.name]
-
-  local nodes = {}
-  -- we don't support weighted consistent hashing
-  local weight = 1
-
-  for _, endpoint in pairs(backend.endpoints) do
-    local endpoint_string = endpoint.address .. ":" .. endpoint.port
-    nodes[endpoint_string] = weight
-  end
-
-  if instance then
-    instance:reinit(nodes)
-  else
-    instance = resty_chash:new(nodes)
-    instances[backend.name] = instance
-  end
-end
-
-return _M