![]() Worker #2 needs the screwdriver, but can't get it because worker #1 is holding it. Worker #1 goes to grab the screw as well, but can't, because it's being held by worker #2. Worker #1 grabs the screwdriver, and worker #2 grabs the screw. In real world terms, consider a construction site: You've got one screwdriver, and one screw. (Say, 3 retries on this particular error before giving up).ĭeadlocks occur when two or more processes requests locks in such a way that the resources being locked overlap, but occur in different orders, so that each process is waiting for a resource that's locked by another process, and that other process is waiting for a lock that the original process has open. you can add this logic to your client code. WHERE datetime <= now() - INTERVAL 900 SECONDĪnother thing to keep in mind is that MySQL documentation suggest that in case of a deadlock the client should retry automatically. if you do (and I suspect you do), order their WHERE in (k1,k2.kn) in ascending order.įix your delete statement to work in ascending order: Make sure you have no other queries that lock access more than one key at a time except for the delete statement. connection 2: locks key( 1), locks key( 2).Now, if you changed your queries such that the connections would lock the keys at the same order, ie: If both run at the same time, connection 1 will lock key(1), connection 2 will lock key(2) and each connection will wait for the other to release the key -> deadlock. connection 2: locks key(2), locks key(1).connection 1: locks key(1), locks key(2).You get a deadlock when two transactions are trying to lock two locks at opposite orders, ie: One easy trick that can help with most deadlocks is sorting the operations in a specific order. Is there a simple way to work around it or lessen its frequency? For example, how exactly do I go about "restarting transaction at Db.pm line 276"? What exactly about my situation is causing the error above? I have seen online that several other people have reported similar errors and that this may be a genuine deadlock situation. ![]() MySQL is a standard Solaris deployment, and the database connection is set up as follows: my $dsn = "DBI:mysql:database=". I haven't done much tuning on MySQL or DBD::mysql. The limit is designed to break their work into small chunks. Note that I am using the a_lock field in file_table to ensure that the four near-identical processes I am running do not try and work on the same row. However, it never happened with a small table and has become more common as the database has grown. The SQL statement that triggers the error is something like this: UPDATE file_table SET a_lock = 'process-1234' WHERE param1 = 'X' AND param2 = 'Y' AND param3 = 'Z' LIMIT 47 One fairly common operation gives rise to the following error sometimes: DBD::mysql::st execute failed: Deadlock found when trying to get lock try restarting transaction at Db.pm line 276. The table has about 10 columns and several indexes. ![]() Cause: .jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock try restarting transaction The error may involve .-Inline The error occurred while setting parameters SQL: update ACT_RU_EXECUTION SET REV_ = ?, IS_ACTIVE_ = ? where ID_ = ? and REV_ = ? Cause: .jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock try restarting transaction at .ExceptionFactory.wrapException(ExceptionFactory.java:30)Īt .(DefaultSqlSession.java:200)Īt .impl.db.DbSqlSession.flushUpdates(DbSqlSession.java:570)Īt .impl.db.DbSqlSession.flush(DbSqlSession.java:359)Īt .(CommandContext.java:192)Īt .(CommandContext.java:61)Īt .(CommandContextInterceptor.java:81)Īt .SpringTransactionInterceptor.lambda$execute$0(SpringTransactionInterceptor.java:56)Īt .TransactionTemplate.execute(TransactionTemplate.java:140)Īt .SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:56)Īt .(LogInterceptor.java:30)Īt .(CommandExecutorImpl.java:56)Īt .(CommandExecutorImpl.java:51)Īt .plete(TaskServiceImpl.I have a MySQL table with about 5,000,000 rows that are being constantly updated in small ways by parallel Perl processes connecting via DBI. ![]()
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