fix sticky session implementation

rootfs/etc/nginx/lua/balancer/sticky.lua

@@ -50,22 +50,17 @@ local function set_cookie(self, value)
   end
 end
 
-local function pick_random(instance)
-  local index = math.random(instance.npoints)
-  return instance:next(index)
-end
-
 function _M.balance(self)
   local cookie, err = ck:new()
   if not cookie then
-    ngx.log(ngx.ERR, err)
-    return pick_random(self.instance)
+    ngx.log(ngx.ERR, "error while initializing cookie: " .. tostring(err))
+    return
   end
 
   local key = cookie:get(self.cookie_name)
   if not key then
-    local tmp_endpoint_string = pick_random(self.instance)
-    key = encrypted_endpoint_string(self, tmp_endpoint_string)
+    local random_str = string.format("%s.%s", ngx.now(), ngx.worker.pid())
+    key = encrypted_endpoint_string(self, random_str)
     set_cookie(self, key)
   end
 

rootfs/etc/nginx/lua/test/balancer/sticky_test.lua

@@ -116,7 +116,8 @@ describe("Sticky", function()
           local cookie_instance = {
             set = function(self, payload)
               assert.equal(payload.key, test_backend.sessionAffinityConfig.cookieSessionAffinity.name)
-              assert.equal(payload.value, util[test_backend_hash_fn .. "_digest"](test_backend_endpoint))
+              local expected_len = #util[test_backend_hash_fn .. "_digest"]("anything")
+              assert.equal(#payload.value, expected_len)
               assert.equal(payload.path, ngx.var.location_path)
               assert.equal(payload.domain, nil)
               assert.equal(payload.httponly, true)