Add cache mechanism for LoadRules in flow module (#268)

* Add cache mechanism for LoadRules in flow module 

Co-authored-by: louyuting <[email protected]>

core/flow/rule_manager.go

@@ -2,6 +2,7 @@ package flow
 
 import (
 	"fmt"
+	"reflect"
 	"sync"
 
 	"github.com/alibaba/sentinel-golang/core/base"
@@ -34,6 +35,7 @@ var (
 		readOnlyMetric:    base.NopReadStat(),
 		writeOnlyMetric:   base.NopWriteStat(),
 	}
+	currentRules = make([]*Rule, 0)
 )
 
 func init() {
@@ -165,12 +167,22 @@ func onRuleUpdate(rules []*Rule) (err error) {
 		}
 	}
 	tcMap = m
+	currentRules = rules
 	return nil
 }
 
 // LoadRules loads the given flow rules to the rule manager, while all previous rules will be replaced.
+// the first returned value indicates whether do real load operation, if the rules is the same with previous rules, return false
 func LoadRules(rules []*Rule) (bool, error) {
 	// TODO: rethink the design
+	tcMux.RLock()
+	isEqual := reflect.DeepEqual(currentRules, rules)
+	tcMux.RUnlock()
+	if isEqual {
+		logging.Info("[Flow] Load rules is the same with current rules, so ignore load operation.")
+		return false, nil
+	}
+
 	err := onRuleUpdate(rules)
 	return true, err
 }

core/flow/rule_manager_test.go

@@ -418,3 +418,27 @@ func Test_buildRulesOfRes(t *testing.T) {
 		assert.True(t, tcs[3].boundStat == stat4)
 	})
 }
+
+func TestLoadRules(t *testing.T) {
+	t.Run("loadSameRules", func(t *testing.T) {
+		_, err := LoadRules([]*Rule{
+			{
+				Resource:               "some-test",
+				Threshold:              10,
+				TokenCalculateStrategy: Direct,
+				ControlBehavior:        Reject,
+			},
+		})
+		assert.Nil(t, err)
+		ok, err := LoadRules([]*Rule{
+			{
+				Resource:               "some-test",
+				Threshold:              10,
+				TokenCalculateStrategy: Direct,
+				ControlBehavior:        Reject,
+			},
+		})
+		assert.Nil(t, err)
+		assert.False(t, ok)
+	})
+}

ext/datasource/helper.go

@@ -51,8 +51,8 @@ func FlowRulesUpdater(data interface{}) error {
 			fmt.Sprintf("Fail to type assert data to []flow.Rule or []*flow.Rule, in fact, data: %+v", data),
 		)
 	}
-	succ, err := flow.LoadRules(rules)
-	if succ && err == nil {
+	_, err := flow.LoadRules(rules)
+	if err == nil {
 		return nil
 	}
 	return NewError(