Converted sticky session balancers into separate classes.

rootfs/etc/nginx/lua/affinity/balanced.lua

@@ -1,57 +0,0 @@
--- An affinity mode which makes sure connections are rebalanced when a deployment is scaled.
--- The advantage of this mode is that the load on the pods will be redistributed.
--- The drawback of this mode is that, when scaling up a deployment, roughly (n-c)/n users 
--- will lose their session, where c is the current number of pods and n is the new number of 
--- pods.
---
--- This class extends/implements the abstract class balancer.sticky.
---
-local math = require("math")
-local resty_chash = require("resty.chash")
-local util = require("util")
-
-local _M = {}
-
--- Consider the situation of N upstreams one of which is failing.
--- Then the probability to obtain failing upstream after M iterations would be close to (1/N)**M.
--- For the worst case (2 upstreams; 20 iterations) it would be ~10**(-6)
--- which is much better then ~10**(-3) for 10 iterations.
-local MAX_UPSTREAM_CHECKS_COUNT = 20
-
-local function get_routing_key(self)
-  return self:get_cookie(), nil
-end
-
-local function set_routing_key(self, key)
-	self:set_cookie(key)
-end
-
-local function pick_new_upstream(self, failed_upstreams)
-  for i = 1, MAX_UPSTREAM_CHECKS_COUNT do
-    local key = string.format("%s.%s.%s", ngx.now() + i, ngx.worker.pid(), math.random(999999))
-
-    local new_upstream = self.instance:find(key)
-
-    if not failed_upstreams[new_upstream] then
-      return new_upstream, key
-    end
-  end
-
-  return nil, nil
-end
-
-function _M.new(self, sticky_balancer, backend)
-  local o = sticky_balancer or {}
-  
-  local nodes = util.get_nodes(backend.endpoints)
-
-  -- override sticky.balancer methods
-  o.instance = resty_chash:new(nodes)
-  o.get_routing_key = get_routing_key
-  o.set_routing_key = set_routing_key
-  o.pick_new_upstream = pick_new_upstream
-
-  return sticky_balancer
-end
-
-return _M