Don't allow same task to be completed by different user at same time

[himanshu_agarwa]

Hey guys,

I want to implement optimistic locking kind of behavior (I know its already been built in), but not sure why this is not working, adding error below. I have a requirement where a task is available in a pool and two users may complete the task at the same time and we need to send error back to the user whose transaction is executed secondly but I get deadlock error rather than task not available or Optmistic locking exception.

Database level isolation level

TX_ISOLATION - REPEATABLE-READ

### Error updating database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
### The error may involve org.activiti.engine.impl.persistence.entity.HistoricTaskInstanceEntity.updateHistoricTaskInstance-Inline
### The error occurred while setting parameters
### SQL: update ACT_HI_TASKINST set       EXECUTION_ID_ = ?,       NAME_ = ?,       PARENT_TASK_ID_ = ?,       DESCRIPTION_ = ?,       OWNER_ = ?,       ASSIGNEE_ = ?,       CLAIM_TIME_ = ?,       END_TIME_ = ?,       DURATION_ = ?,       DELETE_REASON_ = ?,       TASK_DEF_KEY_ = ?,       FORM_KEY_ = ?,       PRIORITY_ = ?,       DUE_DATE_ = ?,       CATEGORY_ = ?     where ID_ = ?
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction] with root cause
com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; 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:404)
   at com.mysql.jdbc.Util.getInstance(Util.java:387)
   at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:950)
   at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3966)
   at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3902)
   at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2526)
   at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2673)
   at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2549)
   at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1861)
   at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1192)
   at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:41)
   at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:66)
   at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:45)
   at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:100)
   at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:75)
   at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:148)
   at org.activiti.engine.impl.db.DbSqlSession.flushUpdates(DbSqlSession.java:870)
   at org.activiti.engine.impl.db.DbSqlSession.flush(DbSqlSession.java:611)
   at org.activiti.engine.impl.interceptor.CommandContext.flushSessions(CommandContext.java:211)
   at org.activiti.engine.impl.interceptor.CommandContext.close(CommandContext.java:137)
   at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:66)
   at org.activiti.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:47)
   at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:133)
   at org.activiti.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:45)
   at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
   at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
   at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:35)
   at org.activiti.engine.impl.TaskServiceImpl.claim(TaskServiceImpl.java:167)
   at com.shutterfly.eni.service.impl.ActivitiServiceImpl.claimAndCompleteTask(ActivitiServiceImpl.java:73)
   at com.shutterfly.eni.service.impl.OrderServiceImpl.submitSbsPlatformOrder(OrderServiceImpl.java:926)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
   at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
   at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
   at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)

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Appreciate, your prompt response.

-Himanshu

[vasile_dirla]

Hi,
I'll try to reproduce and investigate it,
could you please provide a unit test for this scenario? it would be very usefull.
Thanks.