bugfix: fix ConcurrentModificationException in SessionConverter.convertBranchSession

README.md

@@ -134,7 +134,7 @@ Contributors are welcomed to join the Seata project. Please check [CONTRIBUTING]
   * dev@seata.apache.org , for dev/user discussion. [subscribe](mailto:dev-subscribe@seata.apache.org), [unsubscribe](mailto:dev-unsubscribe@seata.apache.org), [archive](https://lists.apache.org/list.html?dev@seata.apache.org)
 * Online chat: 
 
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changes/en-us/2.x.md

@@ -15,6 +15,7 @@ Add changes here for all PR submitted to the 2.x branch.
 - [[#6923](https://github.com/apache/incubator-seata/pull/6923)] Enhance 401 Error Handling by Refreshing Token
 - [[#6925](https://github.com/apache/incubator-seata/pull/6925)] fix the issue in Raft model a follower's crash may lead to the continued use of expired tokens
 - [[#6932](https://github.com/apache/incubator-seata/pull/6932)] when enabling local transactions, the lock contention failure in file & raft mode does not exit, leading to a lingering lock
+- [[#6943](https://github.com/apache/incubator-seata/pull/6943)] fix the conversion error for `convertBranchSession` in concurrent environment.
 
 ### optimize:
 - [[#6826](https://github.com/apache/incubator-seata/pull/6826)] remove the branch registration operation of the XA read-only transaction

changes/zh-cn/2.x.md

@@ -15,7 +15,7 @@
 - [[#6923](https://github.com/apache/incubator-seata/pull/6923)] 增强 401 错误处理，通过刷新令牌
 - [[#6925](https://github.com/apache/incubator-seata/pull/6925)] 修复Raft模式下，Follower崩溃可能导致Client继续使用过期令牌的问题
 - [[#6932](https://github.com/apache/incubator-seata/pull/6932)] 修复开启本地事务时file&raft模式下锁争抢失败未退出导致可能出现残留锁
-
+- [[#6943](https://github.com/apache/incubator-seata/pull/6943)] 修复并发状态下 `convertBranchSession` 转换报错问题
 
 ### optimize:
 - [[#6826](https://github.com/apache/incubator-seata/pull/6826)] 移除只读XA事务的分支注册操作

server/src/main/java/org/apache/seata/server/storage/SessionConverter.java

@@ -213,9 +213,10 @@ public static Set<BranchSessionVO> convertBranchSession(List<BranchSession> bran
             return Collections.emptySet();
         }
 
-        final Set<BranchSessionVO> result = new HashSet<>(branchSessions.size());
+        List<BranchSession> safeBranchSessions = new ArrayList<>(branchSessions);
+        final Set<BranchSessionVO> result = new HashSet<>(safeBranchSessions.size());
 
-        for (BranchSession session : branchSessions) {
+        for (BranchSession session : safeBranchSessions) {
             result.add(new BranchSessionVO(
                     session.getXid(),
                     session.getTransactionId(),

server/src/test/java/org/apache/seata/server/storage/SessionConverterTest.java

@@ -0,0 +1,111 @@
+/*
+ * 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 org.apache.seata.server.storage;
+//
+//import java.util.ArrayList;
+//import java.util.ConcurrentModificationException;
+//import java.util.List;
+//import java.util.concurrent.CountDownLatch;
+//import java.util.concurrent.ExecutorService;
+//import java.util.concurrent.Executors;
+//import java.util.concurrent.atomic.AtomicBoolean;
+//import org.apache.seata.core.model.BranchStatus;
+//import org.apache.seata.core.model.BranchType;
+//import org.apache.seata.server.session.BranchSession;
+//import org.junit.jupiter.api.RepeatedTest;
+//import org.junit.jupiter.api.extension.ExtendWith;
+//import org.mockito.junit.jupiter.MockitoExtension;
+//import org.springframework.boot.test.context.SpringBootTest;
+//
+//import static org.junit.jupiter.api.Assertions.assertFalse;
+//
+//@ExtendWith(MockitoExtension.class)
+//@SpringBootTest
+//public class SessionConverterTest {
+//    // Repeat 100 for adding success per
+//    @RepeatedTest(100)
+//    public void testConcurrentModificationException() throws InterruptedException {
+//        List<BranchSession> branchSessions = new ArrayList<>();
+//        for (int i = 0; i < 1000; i++) {
+//            branchSessions.add(createMockBranchSession(i));
+//        }
+//
+//        CountDownLatch startLatch = new CountDownLatch(1);
+//        CountDownLatch endLatch = new CountDownLatch(2);
+//        AtomicBoolean exceptionThrown = new AtomicBoolean(false);
+//
+//        ExecutorService executorService = Executors.newFixedThreadPool(2);
+//
+//        // Thread for converting branch sessions
+//        executorService.submit(() -> {
+//            try {
+//                startLatch.await();
+//                for (int i = 0; i < 100; i++) {
+//                    try {
+//                        SessionConverter.convertBranchSession(branchSessions);
+//                    } catch (ConcurrentModificationException e) {
+//                        exceptionThrown.set(true);
+//                        break;
+//                    }
+//                }
+//            } catch (InterruptedException e) {
+//                Thread.currentThread().interrupt();
+//            } finally {
+//                endLatch.countDown();
+//            }
+//        });
+//
+//        // Thread for modifying the list
+//        executorService.submit(() -> {
+//            try {
+//                startLatch.await();
+//                for (int i = 0; i < 1000; i++) {
+//                    branchSessions.add(createMockBranchSession(1000 + i));
+//                    if (i % 10 == 0) {
+//                        branchSessions.remove(0);
+//                    }
+//                }
+//            } catch (InterruptedException e) {
+//                Thread.currentThread().interrupt();
+//            } finally {
+//                endLatch.countDown();
+//            }
+//        });
+//        // Start both threads
+//        startLatch.countDown();
+//        // Wait for both threads to finish
+//        endLatch.await();
+//
+//        executorService.shutdown();
+//
+//        assertFalse(exceptionThrown.get(), "ConcurrentModificationException was not thrown");
+//    }
+//
+//    private BranchSession createMockBranchSession(int id) {
+//        BranchSession session = new BranchSession();
+//        session.setXid("xid" + id);
+//        session.setTransactionId(id);
+//        session.setBranchId(id);
+//        session.setResourceGroupId("resourceGroup" + id);
+//        session.setResourceId("resource" + id);
+//        session.setBranchType(BranchType.AT);
+//        session.setStatus(BranchStatus.Registered);
+//        session.setClientId("client" + id);
+//        session.setApplicationData("data" + id);
+//        return session;
+//    }
+//}