Fix chashsubset backend with canary (#7235)

* Fix chashsubset backend with canary

* use floor for buckets calculation to remove hot spot

* Remove testing code

rootfs/etc/nginx/lua/balancer/chashsubset.lua

@@ -25,7 +25,6 @@ local function build_subset_map(backend)
 
   local set_count = math.ceil(#endpoints/subset_size)
   local node_count = set_count * subset_size
-
   -- if we don't have enough endpoints, we reuse endpoints in the last set to
   -- keep the same number on all of them.
   local j = 1
@@ -61,7 +60,9 @@ function _M.new(self, backend)
     instance = resty_chash:new(subset_map),
     hash_by = complex_val,
     subsets = subsets,
-    current_endpoints = backend.endpoints
+    current_endpoints = backend.endpoints,
+    traffic_shaping_policy = backend.trafficShapingPolicy,
+    alternative_backends = backend.alternativeBackends,
   }
   setmetatable(o, self)
   self.__index = self

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

@@ -86,5 +86,21 @@ describe("Balancer chash subset", function()
         assert.are.equal(#endpoints, 3)
       end
     end)
+
+    it("set alternative backends", function()
+      local backend = get_test_backend(7)
+      backend.trafficShapingPolicy  = {
+        weight = 0,
+        header = "",
+        headerValue = "",
+        cookie = ""
+      }
+      backend.alternativeBackends = {
+        "my-dummy-canary-backend"
+      }
+      local instance = balancer_chashsubset:new(backend)
+      assert.not_equal(instance.traffic_shaping_policy, nil)
+      assert.not_equal(instance.alternative_backends, nil)
+    end)
   end)
 end)