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Fault tolerance MySQL Cluster is designed to be very fault tolerant. Although there are issues you should be aware of. This section will cover how cluster is fault tolerant and how your application should work with this. MySQL Server When using MySQL in general temporary errors can happen, that is to say errors that may not occur if the transaction is retried. In MySQL Cluster this can happen more often than other storage engines for a variety of reasons, such as timeouts, node failures or redo log problems. With MySQL Cluster when this happens the transaction will be implicitly rolled-back and the error will be returned to the client. It is up to the client application to retry the transaction. Sometimes the error message returned will not give enough details to find the true cause of the failure, so it is a good idea to run 'SHOW WARNINGS' after an error to see other messages from cluster. For example, if there is a transaction exclusive locking some rows this could happen: mysql> select * from t1; ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction This is kind of useful, but MySQL Cluster has 5 different things that can cause this error. So: mysql> show warnings\G *************************** 1. row *************************** Level: Error Code: 1297 Message: Got temporary error 274 'Time-out in NDB, probably caused by deadlock' from NDB *************************** 2. row *************************** Level: Error Code: 1297 Message: Got temporary error 274 'Time-out in NDB, probably caused by deadlock' from NDB *************************** 3. row *************************** Level: Error Code: 1205 Message: Lock wait timeout exceeded; try restarting transaction *************************** 4. row *************************** Level: Error Code: 1622 Message: Storage engine NDB does not support rollback for this statement. Transaction rolled back and must be restarted 4 rows in set (0.00 sec) So, the error here is NDB error code 274, it is now possible for the MySQL cluster team to find out the cause of this (274 is triggered by TransactionDeadLockDetectionTimeOut exceeded during a scan operation). Heartbeats The data nodes use a system of heartbeats in a ring to make sure that a node's neighbour is still up and running. The heartbeat interval is set using the HeartbeatIntervalDBDB setting which is 1500ms by default. A cluster node will be declared dead if it is not heard from Copyright © 2010, Oracle and/or its affiliates. All rights reserved. 34/81
within 4 heartbeat intervals. This can happen if the data node is overloaded and too busy to send heartbeats on-time or if there are network problems. If any heartbeats are missed it will be logged in the cluster log on the management node. A node's neighbours are decided when a node starts and this information is logged in the node's stdout log. Copyright © 2010, Oracle and/or its affiliates. All rights reserved. 35/81
Page 1 and 2: MySQL Cluster Tutorial O’Reilly M
Page 3 and 4: ndbinfo Data Node Statistics! 39 nd
Page 5 and 6: Introduction MySQL Cluster is a too
Page 7 and 8: MySQL Cluster in short • MySQL Cl
Page 9 and 10: Installation and Configuration In t
Page 11 and 12: Configuration my_Slave.cnf Configur
Page 13 and 14: Starting & Using MySQL Cluster Star
Page 15 and 16: ndb_mgm> show Connected to Manageme
Page 17 and 18: Administer MySQL Cluster MySQL Clus
Page 19 and 20: ndb_mgm> 2 restart Node 2: Node shu
Page 21 and 22: to load problems such as timing iss
Page 23 and 24: MySQL Cluster Manager MySQL Cluster
Page 25 and 26: • The management node(s) can cont
Page 27 and 28: Example configuration Throughout th
Page 29 and 30: example, the MySQL Cluster installa
Page 31 and 32: 3. Fetch the port parameter to conn
Page 33: Introducing MySQL Cluster Manager t
Page 37 and 38: • Stored routines and other none
Page 39 and 40: NDB Info ndbinfo Data Node Statisti
Page 41 and 42: For the redo log space, there is 1
Page 43 and 44: NDB API NDB API Overview The NDB AP
Page 45 and 46: static void run_application(MYSQL &
Page 47 and 48: const NdbDictionary::Index *myPInde
Page 49 and 50: MySQL Cluster Connector for Java Te
Page 51 and 52: • SessionFactory: There is one in
Page 53 and 54: Figure 4: Performance of OpenJPA Ad
Page 55 and 56: config.ini: [ndbd default]noofrepli
Page 57 and 58: The next step is to write the appli
Page 59 and 60: mysql> select * from clusterdb.empl
Page 61 and 62: Compiling and running the ClusterJ
Page 63 and 64: Employee.java: import javax.persist
Page 65 and 66: Main.java (part 2): userTransaction
Page 67 and 68: Main.java (part 4): em.close(); ent
Page 69 and 70: This fails with an error saying the
Page 71 and 72: Scaling and Performance MySQL Nodes
Page 73 and 74: Geographical Replication The MySQL
Page 75 and 76: You can, however, have a more reada
Page 77 and 78: shell> mysql mysql_A:(none)> SHOW M
Page 79 and 80: On the Slave we now issue the CHANG
Page 81: Security It should be noted right f

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