feat: add round robin in remote module

pkg/remoting/loadbalance/loadbalance.go

@@ -37,6 +37,8 @@ func Select(loadBalanceType string, sessions *sync.Map, xid string) getty.Sessio
 		return RandomLoadBalance(sessions, xid)
 	case xidLoadBalance:
 		return XidLoadBalance(sessions, xid)
+	case roundRobinLoadBalance:
+		return RoundRobinLoadBalance(sessions, xid)
 	default:
 		return RandomLoadBalance(sessions, xid)
 	}

pkg/remoting/loadbalance/round_robin_loadbalance.go

@@ -0,0 +1,69 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package loadbalance
+
+import (
+	"math"
+	"sort"
+	"sync"
+	"sync/atomic"
+
+	getty "github.com/apache/dubbo-getty"
+)
+
+var sequence int32
+
+func RoundRobinLoadBalance(sessions *sync.Map, s string) getty.Session {
+	// collect sync.Map adderToSession
+	// filter out closed session instance
+	adderToSession := make(map[string]getty.Session, 0)
+	// map has no sequence, we should sort it to make sure the sequence is always the same
+	adders := make([]string, 0)
+	sessions.Range(func(key, value interface{}) bool {
+		session := key.(getty.Session)
+		if session.IsClosed() {
+			sessions.Delete(key)
+		} else {
+			adderToSession[session.RemoteAddr()] = session
+			adders = append(adders, session.RemoteAddr())
+		}
+		return true
+	})
+	sort.Strings(adders)
+	// adderToSession eq 0 means there are no available session
+	if len(adderToSession) == 0 {
+		return nil
+	}
+	index := getPositiveSequence() % len(adderToSession)
+	return adderToSession[adders[index]]
+}
+
+func getPositiveSequence() int {
+	for {
+		current := atomic.LoadInt32(&sequence)
+		next := current
+		if current == math.MaxInt32 {
+			next = 0
+		} else {
+			next = current + 1
+		}
+		if atomic.CompareAndSwapInt32(&sequence, current, next) {
+			return int(current)
+		}
+	}
+}

pkg/remoting/loadbalance/round_robin_loadbalance_test.go

@@ -0,0 +1,100 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package loadbalance
+
+import (
+	"fmt"
+	"math"
+	"sync"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/seata/seata-go/pkg/remoting/mock"
+)
+
+func TestRoundRobinLoadBalance_Normal(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	sessions := &sync.Map{}
+
+	for i := 0; i < 10; i++ {
+		session := mock.NewMockTestSession(ctrl)
+		session.EXPECT().IsClosed().Return(i == 2).AnyTimes()
+		session.EXPECT().RemoteAddr().Return(fmt.Sprintf("%d", i)).AnyTimes()
+		sessions.Store(session, fmt.Sprintf("session-%d", i+1))
+	}
+
+	for i := 0; i < 10; i++ {
+		if i == 2 {
+			continue
+		}
+		result := RoundRobinLoadBalance(sessions, "some_xid")
+		assert.Equal(t, fmt.Sprintf("%d", i), result.RemoteAddr())
+		assert.NotNil(t, result)
+		assert.False(t, result.IsClosed())
+	}
+}
+
+func TestRoundRobinLoadBalance_OverSequence(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	sessions := &sync.Map{}
+	sequence = math.MaxInt32
+
+	for i := 0; i < 10; i++ {
+		session := mock.NewMockTestSession(ctrl)
+		session.EXPECT().IsClosed().Return(false).AnyTimes()
+		session.EXPECT().RemoteAddr().Return(fmt.Sprintf("%d", i)).AnyTimes()
+		sessions.Store(session, fmt.Sprintf("session-%d", i+1))
+	}
+
+	for i := 0; i < 10; i++ {
+		// over sequence here
+		if i == 0 {
+			result := RoundRobinLoadBalance(sessions, "some_xid")
+			assert.Equal(t, "7", result.RemoteAddr())
+			assert.NotNil(t, result)
+			assert.False(t, result.IsClosed())
+			continue
+		}
+		result := RoundRobinLoadBalance(sessions, "some_xid")
+		assert.Equal(t, fmt.Sprintf("%d", i-1), result.RemoteAddr())
+		assert.NotNil(t, result)
+		assert.False(t, result.IsClosed())
+	}
+}
+
+func TestRoundRobinLoadBalance_All_Closed(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	sessions := &sync.Map{}
+	for i := 0; i < 10; i++ {
+		session := mock.NewMockTestSession(ctrl)
+		session.EXPECT().IsClosed().Return(true).AnyTimes()
+		sessions.Store(session, fmt.Sprintf("session-%d", i+1))
+	}
+	if result := RoundRobinLoadBalance(sessions, "some_xid"); result != nil {
+		t.Errorf("Expected nil, actual got %+v", result)
+	}
+}
+
+func TestRoundRobinLoadBalance_Empty(t *testing.T) {
+	sessions := &sync.Map{}
+	if result := RoundRobinLoadBalance(sessions, "some_xid"); result != nil {
+		t.Errorf("Expected nil, actual got %+v", result)
+	}
+}