Changes in MySQL NDB Cluster 7.6.10 (5.7.26-ndb-7.6.10) (2019-04-26, General Availability)

MySQL NDB Cluster 7.6.10 is a new release of NDB 7.6, based on MySQL Server 5.7 and including features in version 7.6 of the NDB storage engine, as well as fixing recently discovered bugs in previous NDB Cluster releases.

Obtaining NDB Cluster 7.6.  NDB Cluster 7.6 source code and binaries can be obtained from https://dev.mysql.com/downloads/cluster/.

For an overview of changes made in NDB Cluster 7.6, see What is New in NDB Cluster 7.6.

This release also incorporates all bug fixes and changes made in previous NDB Cluster releases, as well as all bug fixes and feature changes which were added in mainline MySQL 5.7 through MySQL 5.7.26 (see Changes in MySQL 5.7.26 (2019-04-25, General Availability)).

Bugs Fixed

• NDB Disk Data: The error message returned when validation of MaxNoOfOpenFiles in relation to InitialNoOfOpenFiles failed has been improved to make the nature of the problem clearer to users. (Bug #28943749)

• NDB Disk Data: Repeated execution of ALTER TABLESPACE ... ADD DATAFILE against the same tablespace caused data nodes to hang and left them, after being killed manually, unable to restart. (Bug #22605467)

• NDB Cluster APIs: NDB now identifies short-lived transactions not needing the reduction of lock contention provided by NdbBlob::close() and no longer invokes this method in cases (such as when autocommit is enabled) in which unlocking merely causes extra work and round trips to be performed prior to committing or aborting the transaction. (Bug #29305592)

  References: See also: Bug #49190, Bug #11757181.

• NDB Cluster APIs: When the most recently failed operation was released, the pointer to it held by NdbTransaction became invalid and when accessed led to failure of the NDB API application. (Bug #29275244)

• When a pushed join executing in the DBSPJ block had to store correlation IDs during query execution, memory for these was allocated for the lifetime of the entire query execution, even though these specific correlation IDs are required only when producing the most recent batch in the result set. Subsequent batches require additional correlation IDs to be stored and allocated; thus, if the query took sufficiently long to complete, this led to exhaustion of query memory (error 20008). Now in such cases, memory is allocated only for the lifetime of the current result batch, and is freed and made available for re-use following completion of the batch. (Bug #29336777)

  References: See also: Bug #26995027.

• API and data nodes running NDB 7.6 and later could not use an existing parsed configuration from an earlier release series due to being overly strict with regard to having values defined for configuration parameters new to the later release, which placed a restriction on possible upgrade paths. Now NDB 7.6 and later are less strict about having all new parameters specified explicitly in the configuration which they are served, and use hard-coded default values in such cases. (Bug #28993400)

• Added DUMP 406 (NdbfsDumpRequests) to provide NDB file system information to global checkpoint and local checkpoint stall reports in the node logs. (Bug #28922609)

• A race condition between the DBACC and DBLQH kernel blocks occurred when different operations in a transaction on the same row were concurrently being prepared and aborted. This could result in DBTUP attempting to prepare an operation when a preceding operation had been aborted, which was unexpected and could thus lead to undefined behavior including potential data node failures. To solve this issue, DBACC and DBLQH now check that all dependencies are still valid before attempting to prepare an operation.

  Note

  This fix also supersedes a previous one made for a related issue which was originally reported as Bug #28500861.

  (Bug #28893633)

• The ndbinfo.cpustat table reported inaccurate information regarding send threads. (Bug #28884157)

• Execution of an LCP_COMPLETE_REP signal from the master while the LCP status was IDLE led to an assertion. (Bug #28871889)

• Issuing a STOP command in the ndb_mgm client caused ndbmtd processes which had recently been added to the cluster to hang in Phase 4 during shutdown. (Bug #28772867)

• In some cases, one and sometimes more data nodes underwent an unplanned shutdown while running ndb_restore. This occurred most often, but was not always restircted to, when restoring to a cluster having a different number of data nodes from the cluster on which the original backup had been taken.

  The root cause of this issue was exhaustion of the pool of SafeCounter objects, used by the DBDICT kernel block as part of executing schema transactions, and taken from a per-block-instance pool shared with protocols used for NDB event setup and subscription processing. The concurrency of event setup and subscription processing is such that the SafeCounter pool can be exhausted; event and subscription processing can handle pool exhaustion, but schema transaction processing could not, which could result in the node shutdown experienced during restoration.

  This problem is solved by giving DBDICT schema transactions an isolated pool of reserved SafeCounters which cannot be exhausted by concurrent NDB event activity. (Bug #28595915)

• After a commit failed due to an error, mysqld shut down unexpectedly while trying to get the name of the table involved. This was due to an issue in the internal function ndbcluster_print_error(). (Bug #28435082)

• ndb_restore did not restore autoincrement values correctly when one or more staging tables were in use. As part of this fix, we also in such cases block applying of the SYSTAB_0 backup log, whose content continued to be applied directly based on the table ID, which could ovewrite the autoincrement values stored in SYSTAB_0 for unrelated tables. (Bug #27917769, Bug #27831990)

  References: See also: Bug #27832033.

• ndb_restore employed a mechanism for restoring autoincrement values which was not atomic, and thus could yield incorrect autoincrement values being restored when multiple instances of ndb_restore were used in parallel. (Bug #27832033)

  References: See also: Bug #27917769, Bug #27831990.

• Neither the MAX_EXECUTION_TIME optimizer hint nor the max_execution_time system variable was respected for DDL statements or queries against INFORMATION_SCHEMA tables while an NDB global schema lock was in effect. (Bug #27538139)

• When query memory was exhausted in the DBSPJ kernel block while storing correlation IDs for deferred operations, the query was aborted with error status 20000 Query aborted due to out of query memory. (Bug #26995027)

  References: See also: Bug #86537.

• MaxBufferedEpochs is used on data nodes to avoid excessive buffering of row changes due to lagging NDB event API subscribers; when epoch acknowledgements from one or more subscribers lag by this number of epochs, an asynchronous disconnection is triggered, allowing the data node to release the buffer space used for subscriptions. Since this disconnection is asynchronous, it may be the case that it has not completed before additional new epochs are completed on the data node, resulting in new epochs not being able to seize GCP completion records, generating warnings such as those shown here:

      [ndbd] ERROR    -- c_gcp_list.seize() failed...
  
      ...
  
      [ndbd] WARNING  -- ACK wo/ gcp record...

  And leading to the following warning:

      Disconnecting node %u because it has exceeded MaxBufferedEpochs
      (100 > 100), epoch ....

  This fix performs the following modifications:

  • Modifies the size of the GCP completion record pool to ensure that there is always some extra headroom to account for the asynchronous nature of the disconnect processing previously described, thus avoiding c_gcp_list seize failures.

  • Modifies the wording of the MaxBufferedEpochs warning to avoid the contradictory phrase “100 > 100”.

  (Bug #20344149)

• When executing the redo log in debug mode it was possible for a data node to fail when deallocating a row. (Bug #93273, Bug #28955797)

• An NDB table having both a foreign key on another NDB table using ON DELETE CASCADE and one or more TEXT or BLOB columns leaked memory.

  As part of this fix, ON DELETE CASCADE is no longer supported for foreign keys on NDB tables when the child table contains a column that uses any of the BLOB or TEXT types. (Bug #89511, Bug #27484882)