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MySQL Cluster 7.6.10 has been released
Posted by: Lars Tangvald
Date: April 27, 2019 03:25AM

Dear MySQL Users,

MySQL Cluster is the distributed, shared-nothing variant of MySQL.
This storage engine provides:

  - In-Memory storage - Real-time performance (with optional
    checkpointing to disk)
  - Transparent Auto-Sharding - Read & write scalability
  - Active-Active/Multi-Master geographic replication

  - 99.999% High Availability with no single point of failure
    and on-line maintenance
  - NoSQL and SQL APIs (including C++, Java, http, Memcached
    and JavaScript/Node.js)

MySQL Cluster 7.6.10 has been released and can be downloaded from

where you will also find Quick Start guides to help you get your
first MySQL Cluster database up and running.

MySQL Cluster 7.6 is also available from our repository for Linux
platforms, go here for details:

The release notes are available from

MySQL Cluster enables users to meet the database challenges of next
generation web, cloud, and communications services with uncompromising
scalability, uptime and agility.

More details can be found at

Enjoy !

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

   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

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

     * 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

     * 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
       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

     * 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. (Bug #27484882)

     * 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 acjknowledgements 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 >
       (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)

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MySQL Cluster 7.6.10 has been released
April 27, 2019 03:25AM

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