背景
最近在排查問題時發現，偶爾會發生關於數據庫鎖超時的現象，會發生像如下的報錯信息：
Exception in thread "pool-3-thread-1" org.springframework.dao.CannotAcquireLockException:
### Error updating database. Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction
### The error may involve com.zr.center.mybatis.auto.mapper.UserMapper.updateByExampleSelective-Inline
### The error occurred while setting parameters
### SQL: update user SET user_name = ? WHERE ( user_id = ? )
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction
; ]; Lock wait timeout exceeded; try restarting transaction; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction
at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:262)
at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)
at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:75)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:447)
at com.sun.proxy.$Proxy101.update(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.update(SqlSessionTemplate.java:295)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:59)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)
at com.sun.proxy.$Proxy103.updateByExampleSelective(Unknown Source)
at com.zr.center.framework.web.service.BaseService.updateByExampleSelective(BaseService.java:97)
at com.zr.center.api.test.service.TestService.updateUserName(TestService.java:34)
at com.zr.center.api.test.service.TestService$$FastClassBySpringCGLIB$$bd3aa32.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:746)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:294)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688)
at com.zr.center.api.test.service.TestService$$EnhancerBySpringCGLIB$$59b19302.updateUserName(<generated>)
at com.zr.center.ApplicationTests.lambda$testTxLockWaiting$0(ApplicationTests.java:32)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.Util.getInstance(Util.java:408)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:952)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3976)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3912)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2530)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2683)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2486)
排查
經過排查，DBA給出的日志中並未有死鎖，死鎖的原因排除，查詢業務日志發現在高並發的時期有時會有重復請求過來，也有一個服務在處理某個邏輯時會發一條mq消息，而同時會消費這條消息，此時也會導致鎖超時。超時原因就是因為一個事務中處理的邏輯過多，有調外部服務(超時)，有更新其它多張表的操作，這樣就會導致后面事務請求超時，報以上錯誤。
重現步驟
-
數據庫配置
關於配置信息查看，可以看到事務隔離是RR,事務鎖等待時長為默認的50s
-
事務代碼
/**
* @description: 用戶服務超時測試
* @author: chong guo
* @create: 2018-12-10 14:44
*/
@Service
@Slf4j
public class TestService extends BaseService<User, UserExample, Long> {
/**
* 更新用戶名稱
*
* @param userId
* @param name
*/
@Transactional(rollbackFor = Exception.class)
public void updateUserName(Long userId, String name) throws InterruptedException {
log.info("開始更新用戶名【{}】，用戶ID為【{}】", name, userId);
UserExample userExample = new UserExample();
userExample.createCriteria().andUserIdEqualTo(userId);
User user = new User();
user.setUserName(name);
super.updateByExampleSelective(user, userExample);
// 模擬業務超時，有可能調用外部遠程服務超時，也有可能處理其它邏輯
Thread.sleep(55000);
log.info("結束更新用戶名【{}】，用戶ID為【{}】", name, userId);
}
}
-
模擬並發
/**
* @author Chong Guo
*/
@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
public class ApplicationTests {
@Resource
TestService testService;
private final int threadCount = 5;
@Test
public void testTxLockWaiting() throws InterruptedException {
CountDownLatch countDownLatch = new CountDownLatch(threadCount);
ExecutorService threadPool = Executors.newFixedThreadPool(300);
for (int i = 0; i < threadCount; i++) {
threadPool.execute(() -> {
try {
testService.updateUserName(611526166943105024L, "chongguo");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
countDownLatch.countDown();
}
});
}
countDownLatch.await();
threadPool.shutdown();
log.info("Test tx lock is over");
Thread.sleep(100000);
}
}
運行代碼后會現三次失敗，二次成功，失敗原因都是鎖超時
總結
- 代碼優化，將大事務中無關的邏輯拆出來，異步處理
- 業務提供方涉及到外部調用的接口需要把超時時長設置短一些
- 如果調用方有重試機制，可以針對業務去掉重試，將connetion time設置大一些