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MySQL Cluster 8.0.21 has been released
Posted by: Jocelyn Ramilison
Date: July 13, 2020 06:43AM

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

  - 99.9999% 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 8.0.21 has been released and can be downloaded from

  http://www.mysql.com/downloads/cluster/

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

The release notes are available from

  http://dev.mysql.com/doc/relnotes/mysql-cluster/8.0/en/index.html

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

  http://www.mysql.com/products/cluster/

Enjoy !

Changes in MySQL NDB Cluster 8.0.21 (2020-07-13, General Availability)

   MySQL NDB Cluster 8.0.21 is a new release of NDB 8.0, based
   on MySQL Server 8.0 and including features in version 8.0 of
   the NDB storage engine, as well as fixing recently discovered
   bugs in previous NDB Cluster releases.

   Obtaining NDB Cluster 8.0.  NDB Cluster 8.0 source code and
   binaries can be obtained from
   https://dev.mysql.com/downloads/cluster/.

   For an overview of changes made in NDB Cluster 8.0, see What
   is New in NDB Cluster
   (https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-what-is-new.html).

   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 8.0
   through MySQL 8.0.21 (see Changes in MySQL 8.0.21 (2020-07-13,
   General Availability)
   (https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-21.html)).


Packaging Notes


     * For Windows, MSI installer packages for MySQL Cluster now
       include a check for the required Visual Studio
       redistributable package, and produce a message asking the
       user to install it if it is missing. (Bug #30541398)

Functionality Added or Changed


     * NDB Disk Data: An initial restart of the cluster now
       causes the removal of all NDB tablespaces and log file
       groups from the NDB dictionary and the MySQL data
       dictionary. This includes the removal of all data files
       and undo log files associated with these objects. (Bug
       #30435378)
       References: See also: Bug #29894166.

     * The status variable Ndb_metadata_blacklist_size is now
       deprecated, and is replaced in NDB 8.0.22 by
       Ndb_metadata_excluded_count. (Bug #31465469)

     * It now possible to consolidate data from separate
       instances of NDB Cluster into a single target NDB Cluster
       when the original datasets all use the same schema. This
       is supported when using backups created using START
       BACKUP in ndb_mgm and restoring them with ndb_restore,
       using the --remap-column option implemented in this
       release (along with --restore-data and possibly other
       options). --remap-column can be employed to handle cases
       of overlapping primary, unique, or both sorts of key
       values between source clusters, and you need to make sure
       that they do not overlap in the target cluster. This can
       also be done to preserve other relationships between
       tables.
       When used together with --restore-data, the new option
       applies a function to the value of the indicated column.
       The value set for this option is a string of the format
       db.tbl.col:fn:args, whose components are listed here:

          + db: Database name, after performing any renames.

          + tbl: Table name.

          + col: Name of the column to be updated. This column's
            type must be one of INT or BIGINT, and can
            optionally be UNSIGNED.

          + fn: Function name; currently, the only supported
            name is offset.

          + args: The size of the offset to be added to the
            column value by offset. The range of the argument is
            that of the signed variant of the column's type;
            thus, negative offsets are supported.
       You can use --remap-column for updating multiple columns
       of the same table and different columns of different
       tables, as well as combinations of multiple tables and
       columns. Different offset values can be employed for
       different columns of the same table.
       As part of this work, two new options are also added to
       ndb_desc in this release:

          + --auto-inc (short form -a): Includes the the next
            auto-increment value in the output, if the table has
            an AUTO_INCREMENT column.

          + --context (short form -x): Provides extra
            information about the table, including the schema,
            database name, table name, and internal ID.
       These options may be useful for obtaining information
       about NDB tables when planning a merge, particularly in
       situations where the mysql client may not be readily
       available.
       For more information, see the descriptions for
       --remap-column, --auto-inc, and --context. (Bug
       #30383950)

     * Detailed real-time information about the state of
       automatic metadata mismatch detection and synchronization
       can now be obtained from tables in the MySQL Performance
       Schema. These two tables are listed here:

          + ndb_sync_pending_objects: Contains information about
            NDB database objects for which mismatches have been
            detected between the NDB dictionary and the MySQL
            data dictionary. It does not include objects which
            have been excluded from mismatch detection due to
            permanent errors raised when attempting to
            synchronize them.

          + ndb_sync_excluded_objects: Contains information
            about NDB database objects which have been excluded
            because they cannot be synchronized between the NDB
            dictionary and the MySQL data dictionary, and thus
            require manual intervention. These objects are no
            longer subject to mismatch detection until such
            intervention has been performed.
       In each of these tables, each row corresponds to a
       database object, and contains the database object's
       parent schema (if any), the object's name, and the
       object's type. Types of objects include schemas,
       tablespaces, log file groups, and tables. The
       ndb_sync_excluded_objects table shows in addition to this
       information the reason for which the object has been
       excluded.
       Performance Schema NDB Cluster Tables
       (https://dev.mysql.com/doc/refman/8.0/en/performance-schema-ndb-cluster-tables.html)
       , provides further information about these Performance
       Schema tables. (Bug #30107543)

     * ndb_restore now supports different primary key
       definitions for source and target tables when restoring
       from an NDB native backup, using the --allow-pk-changes
       option introduced in this release. Both increasing and
       decreasing the number of columns making up the original
       primary key are supported. This may be useful when it is
       necessary to accommodate schema version changes while
       restoring data, or when doing so is more efficient or
       less time-consuming than performing ALTER TABLE
       statements involving primary key changes on a great many
       tables following the restore operation.
       When extending a primary key with additional columns, any
       columns added must not be nullable, and any values stored
       in any such columns must not change while the backup is
       being taken. Changes in the values of any such column
       while trying to add it to the table's primary key causes
       the restore operation to fail. Due to the fact that some
       applications set the values of all columns when updating
       a row even if the values of one or more of the columns
       does not change, it is possible to override this behavior
       by using the --ignore-extended-pk-updates option which is
       also added in this release. If you do this, care must be
       taken to insure that such column values do not actually
       change.
       When removing columns from the table's primary key, it is
       not necessary that the columns dropped from the primary
       key remain part of the table afterwards.
       For more information, see the description of the
       --allow-pk-changes option in the documentation for
       ndb_restore. (Bug #26435136, Bug #30383947, Bug
       #30634010)

     * Added the --ndb-log-fail-terminate option for mysqld.
       When used, this causes the SQL node to terminate if it is
       unable to log all row events. (Bug #21911930)
       References: See also: Bug #30383919.

     * When a scalar subquery has no outer references to the
       table to which the embedding condition is attached, the
       subquery may be evaluated independent of that table; that
       is, the subquery is not dependent. NDB now attempts to
       identify and evaluate such a subquery before trying to
       retrieve any rows from the table to which it is attached,
       and to use the value thus obtained in a pushed condition,
       rather than using the subquery which provided the value.

     * In MySQL 8.0.17 and later, the MySQL Optimizer transforms
       NOT EXISTS and NOT IN queries into antijoins. NDB can now
       push these down to the data nodes.
       This can be done when there is no unpushed condition on
       the table, and the query fulfills any other conditions
       which must be met for an outer join to be pushed down.

Bugs Fixed


     * Important Change; NDB Disk Data: An online change of
       tablespace is not supported for NDB tables. Now, for an
       NDB table, the statement ALTER TABLE ndb_table ...
       ALGORITHM=INPLACE, TABLESPACE=new_tablespace is
       specifically disallowed.
       As part of this fix, the output of the ndb_desc utility
       is improved to include the tablespace name and ID for an
       NDB table which is using one. (Bug #31180526)

     * The wrong index was used in the array of indexes while
       dropping an index. For a table with 64 indexes this
       caused uninitialized memory to be released. This problem
       also caused a memory leak when a new index was created at
       any later time following the drop. (Bug #31408095)

     * Removed an unnecessary dependency of ndb_restore on the
       NDBCLUSTER plugin. (Bug #31347684)

     * Objects for which auto-synchronization fails due to
       temporary errors, such as failed acquisitions of metadata
       locks, are simply removed from the list of detected
       objects, making such objects eligible for detection in
       later cycles in which the synchronization is retried and
       hopefully succeeds. This best-effort approach is suitable
       for the default auto-synchronization behaviour but is not
       ideal when the using the ndb_metadata_sync system
       variable, which triggers synchronization of all metadata,
       and when synchronization is complete, is automatically
       set to false to indicate that this has been done.
       What happened, when a temporary error persisted for a
       sizable length of time, was that metadata synchronization
       could take much longer than expected and, in extreme
       cases, could hang indefinitely, pending user action. One
       such case occurred when using ndb_restore with the
       --disable-indexes option to restore metadata, when the
       synchronization process entered a vicious cycle of
       detection and failed synchronization attempts due to the
       missing indexes until the indexes were rebuilt using
       ndb_restore --rebuild-indexes.
       The fix for this issue is, whenever ndb_metadata_sync is
       set to true, to exclude an object after synchronization
       of it fails 10 times with temporary errors by promoting
       these errors to a permanent error, in order to prevent
       stalling. This is done by maintaining a list of such
       objects, this list including a count of the number of
       times each such object has been retried. Validation of
       this list is performed during change detection in a
       similar manner to validation of the exclusion list. (Bug
       #31341888)

     * 32-bit platforms are not supported by NDB 8.0. Beginning
       with this release, the build process checks the system
       architecture and aborts if it is not 64-bit. (Bug
       #31340969)

     * Page-oriented allocations on the data nodes are divided
       into nine resource groups, some having pages dedicated to
       themselves, and some having pages dedicated to shared
       global memory which can be allocated by any resource
       group. To prevent the query memory resource group from
       depriving other, more important resource groups such as
       transaction memory of resources, allocations for query
       memory are performed with low priority and are not
       allowed to use the last 10% of shared global memory. This
       change was introduced by poolification work done in NDB
       8.0.15.
       Subsequently, it was observed that the calculation for
       the number of pages of shared global memory kept
       inaccessible to query memory was correct only when no
       pages were in use, which is the case when the LateAlloc
       data node parameter is disabled (0).
       This fix corrects that calculation as performed when
       LateAlloc is enabled. (Bug #31328947)
       References: See also: Bug #31231286.

     * Multi-threaded restore is able to drive greater cluster
       load than the previous single-threaded restore,
       especially while restoring of the data file. To avoid
       load-related issues, the insert operation parallelism
       specified for an ndb_restore instance is divided equally
       among the part threads, so that a multithreaded instance
       has a similar level of parallelism for transactions and
       operations to a single-threaded instance.
       An error in division caused some part threads to have
       lower insert operation parallelism than they should have,
       leading to an slower restore than expected. This fix
       ensures all part threads in a multi-threaded ndb_restore
       instance get an equal share for parallelism. (Bug
       #31256989)

     * DUMP 1001 (DumpPageMemoryOnFail) now prints out
       information about the internal state of the data node
       page memory manager when allocation of pages fails due to
       resource constraints. (Bug #31231286)

     * Statistics generated by NDB for use in tracking internal
       objects allocated and deciding when to release them were
       not calculated correctly, with the result that the
       threshold for resource usage was 50% higher than
       intended. This fix corrects the issue, and should allow
       for reduced memory usage. (Bug #31127237)

     * An excessive number of entries were written to the backup
       log when performing an online backup, using ndbmtd on the
       data nodes. This happened because row changes occurring
       to fragments managed by LDM instance 1 were always
       recorded in the log, even when they were for primary
       fragments other than primary fragments. This wasted
       resources when restoring from the backup, and could cause
       other problems when doing so, such as when using staging
       tables for schema transforms while executing ndb_restore.
       (Bug #31034270)

     * The Dojo toolkit included with NDB Cluster and used by
       the Auto-Installer was upgraded to version 1.15.3. (Bug
       #31029110)

     * A packed version 1 configuration file returned by
       ndb_mgmd could contain duplicate entries following an
       upgrade to NDB 8.0, which made the file incompatible with
       clients using version 1. This occurs due to the fact that
       the code for handling backwards compatibility assumed
       that the entries in each section were already sorted when
       merging it with the default section. To fix this, we now
       make sure that this sort is performed prior to merging.
       (Bug #31020183)

     * When executing any of the SHUTDOWN, ALL STOP, or ALL
       RESTART management commands, it is possible for different
       nodes to attempt to stop on different global checkpoint
       index (CGI) boundaries. If they succeed in doing so, then
       a subsequent system restart is slower than normal because
       any nodes having an earlier stop GCI must undergo
       takeover as part of the process. When nodes failing on
       the first GCI boundary cause surviving nodes to be
       nonviable, surviving nodes suffer an arbitration failure;
       this has the positive effect of causing such nodes to
       halt at the correct GCI, but can give rise to spurious
       errors or similar.
       To avoid such issues, extra synchronization is now
       performed during a planned shutdown to reduce the
       likelihood that different data nodes attempt to shut down
       at different GCIs as well as the use of unnecessary node
       takeovers during system restarts. (Bug #31008713)

     * During an upgrade, a client could connect to an NDB 8.0
       data node without specifying a multiple transporter
       instance ID, so that this ID defaulted to -1. Due to an
       assumption that this would occur only in the Node
       starting state with a single transporter, the node could
       hang during the restart. (Bug #30899046)

     * When an NDB cluster was upgraded from a version that does
       not support the data dictionary to one that does, any DDL
       executed on a newer SQL node was not properly distributed
       to older ones. In addition, newer SDI generated during
       DDL execution was ignored by any data nodes that had not
       yet been upgraded. These two issues led to schema states
       that were not consistent between nodes of different NDB
       software versions.
       We fix this problem by blocking any DDL affecting NDB
       data objects while an upgrade from a previous NDB version
       to a version with data dictionary support is ongoing.
       (Bug #30877440)
       References: See also: Bug #30184658.

     * The mysql.ndb_schema table, used internally for schema
       distribution among SQL nodes, has been modified in NDB
       8.0. When a cluster is being upgraded from a older
       version of NDB, the first SQL node to be upgraded updates
       the definition of this table to match that used by NDB
       8.0 GA releases. (For this purpose, NDB now uses 8.0.21
       as the cutoff version.) This is done by dropping the
       existing table and re-creating it using the newer
       definition. SQL nodes which have not yet been upgraded
       receive this ndb_schema table drop event and enter
       read-only mode, becoming writable again only after they
       are upgraded.
       To keep SQL nodes running older versions of NDB from
       going into read-only mode, we change the upgrade behavior
       of mysqld such that the ndb_schema table definition is
       updated only if all SQL nodes connected to the cluster
       are running an 8.0 GA version of NDB and thus having the
       updated ndb_schema table definition. This means that,
       during an upgrade to the current or any later version, no
       MySQL Server that is being upgraded updates the
       ndb_schema table if there is at least one SQL node with
       an older version connected to the cluster. Any SQL node
       running an older version of NDB remains writable
       throughout the upgrade process. (Bug #30876990, Bug
       #31016905)

     * When mysqld was upgraded to a version that used a new SDI
       version, all NDB tables become inaccessible. This was
       because, during an upgrade, synchronization of NDB tables
       relies on deserializing the SDI packed into the NDB
       Dictionary; if the SDI format was of an version older
       than that used prior to the upgrade, deserialization
       could not take place if the format was not the same as
       that of the new version, which made it impossible to
       create a table object in the MySQL data dictionary.
       This is fixed by making it possible for NDB to bypass the
       SDI version check in the MySQL server when necessary to
       perform deserialization as part of an upgrade. (Bug
       #30789293, Bug #30825260)

     * When responding to a SCANTABREQ, an API node can provide
       a distribution key if it knows that the scan should work
       on only one fragment, in which case the distribution key
       should be the fragment ID, but in some cases a hash of
       the partition key was used instead, leading to failures
       in DBTC. (Bug #30774226)

     * Several memory leaks found in ndb_import have been
       removed. (Bug #30756434, Bug #30727956)

     * The master node in a backup shut down unexpectedly on
       receiving duplicate replies to a DEFINE_BACKUP_REQ
       signal. These occurred when a data node other than the
       master errored out during the backup, and the backup
       master handled the situation by sending itself a
       DEFINE_BACKUP_REF signal on behalf of the missing node,
       which resulted in two replies being received from the
       same node (a CONF signal from the problem node prior to
       shutting down and the REF signal from the master on
       behalf of this node), even though the master expected
       only one reply per node. This scenario was also
       encountered for START_BACKUP_REQ and STOP_BACKUP_REQ
       signals.
       This is fixed in such cases by allowing duplicate replies
       when the error is the result of an unplanned node
       shutdown. (Bug #30589827)

     * When processing a CSV file, ndb_import did not accept
       trailing field terminators at the ends of lines that were
       accepted by mysqlimport. (Bug #30434663)

     * When updating NDB_TABLE comment options using ALTER
       TABLE, other options which has been set to non-default
       values when the table was created but which were not
       specified in the ALTER TABLE statement could be reset to
       their defaults.
       See Setting NDB_TABLE Options
       (https://dev.mysql.com/doc/refman/8.0/en/create-table-ndb-table-comment-options.html)
       , for more information. (Bug #30428829)

     * Removed a memory leak found in the ndb_import utility.
       (Bug #29820879)

     * Incorrect handling of operations on replicas during node
       restarts could result in a forced shutdown, or in content
       diverging between replicas, when primary keys with
       nonbinary (case-sensitive) equality conditions were used.
       (Bug #98526, Bug #30884622)

On Behalf of Oracle/MySQL Release Engineering Team,
Hery Ramilison


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