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MySQL Cluster 7.6.6 GA has been released
Posted by: Jocelyn Ramilison
Date: June 01, 2018 06:48AM

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-Paritioning (Sharding) - Read & write scalability
- Transactional consistency across partitioned and distributed datasets
- Parallel cross partition queries such as joins
- Active-Active/Multi-Master geographic replication
- 99.9999% High Availability with on-line maintenance and no single point of
- NoSQL and SQL APIs (including C++, Java, http, Memcached
and JavaScript/Node.js)

MySQL Cluster 7.6.6 GA, 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.

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 7.6.6 (5.7.22-ndb-7.6.6) (2018-05-31, General Availability)

MySQL NDB Cluster 7.6.6 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 5.7.22 (see Changes in MySQL 5.7.22
(2018-04-19, General Availability)

Functionality Added or Changed

* When performing an NDB backup, the ndbinfo.logbuffers
table now displays information regarding buffer usage by
the backup process on each data node. This is implemented
as rows reflecting two new log types in addition to REDO
and DD-UNDO. One of these rows has the log type
BACKUP-DATA, which shows the amount of data buffer used
during backup to copy fragments to backup files. The
other row has the log type BACKUP-LOG, which displays the
amount of log buffer used during the backup to record
changes made after the backup has started. One each of
these log_type rows is shown in the logbuffers table for
each data node in the cluster. Rows having these two log
types are present in the table only while an NDB backup
is currently in progress. (Bug #25822988)

* Added the --logbuffer-size option for ndbd and ndbmtd,
for use in debugging with a large number of log messages.
This controls the size of the data node log buffer; the
default (32K) is intended for normal operations.
(Bug #89679, Bug #27550943)

* The previously experimental shared memory (SHM)
transporter is now supported in production. SHM works by
transporting signals through writing them into memory,
rather than on a socket. NDB already attempts to use SHM
automatically between data nodes and API nodes sharing
the same host. To enable explicit shared memory
connections, set the UseShm SHM configuration parameter
to true. When explicitly defining shared memory as the
connection method, it is also necessary to identify the
nodes at either end of the connection (NodeId1 and
NodeId2 parameters), and to provide a shared memory key
(ShmKey). In addition, to improve performance, it is also
possible to set a spin time (ShmSpinTime) for the SHM
Configuration of SHM is otherwise similar to that of the
TCP transporter. NDB Cluster Shared-Memory Connections
, provides additional information.

* The SPJ kernel block now takes into account when it is
evaluating a join request in which at least some of the
tables are used in inner joins. This means that SPJ can
eliminate requests for rows or ranges as soon as it
becomes known that a preceding request did not return any
results for a parent row. This saves both the data nodes
and the SPJ block from having to handle requests and
result rows which never take part in a result row from an
inner join.
When upgrading from NDB 7.6.5 or earlier, you should be
aware that this optimization depends on both API client
and data node functionality, and so is not available
until all of these have been upgraded.

* The poll receiver which NDB uses to read from sockets,
execute messages from the sockets, and wake up other
threads now offloads wakeup of other threads to a new
thread that wakes up the other threads on request, and
otherwise simply sleeps. This improves the scalability of
a single cluster connection by keeping the receive thread
from becoming overburdened by tasks including wakeup of
other threads.

Bugs Fixed

* Important Change; NDB Client Programs: ndb_top ignored
short forms of command-line options, and did not in all
cases handle misformed long options correctly. As part of
the fix for these issues, the following changes have been
made to command-line options used with ndb_top to bring
them more into line with those used with other NDB
Cluster and MySQL programs:

+ The --passwd option is removed, and replaced by
--password (short form -p).

+ The short form -t for the --port option has been
replaced by -P.

+ The short form -x for the --text option has been
replaced by -t.
(Bug #26907833)
References: See also: Bug #88236, Bug #20733646.

* NDB Cluster APIs: A previous fix for an issue, in which
the failure of multiple data nodes during a partial
restart could cause API nodes to fail, did not properly
check the validity of the associated NdbReceiver object
before proceeding. Now in such cases an invalid object
triggers handling for invalid signals, rather than a node
failure. (Bug #25902137)
References: This issue is a regression of: Bug #25092498.

* NDB Cluster APIs: Incorrect results, usually an empty
result set, were returned when setBound() was used to
specify a NULL bound. This issue appears to have been
caused by a problem in gcc, limited to cases using the
old version of this method (which does not employ
NdbRecord), and is fixed by rewriting the problematic
internal logic in the old implementation. (Bug #89468,
Bug #27461752)

* NDB Cluster APIs: Released NDB API objects are kept in
one or more Ndb_free_list structures for later reuse.
Each list also keeps track of all objects seized from it,
and makes sure that these are eventually released back to
it. In the event that the internal function
NdbScanOperation::init() failed, it was possible for an
NdbApiSignal already allocated by the NdbOperation to be
leaked. Now in such cases, NdbScanOperation::release() is
called to release any objects allocated by the failed
NdbScanOperation before it is returned to the free list.
This fix also handles a similar issue with
NdbOperation::init(), where a failed call could also leak
a signal. (Bug #89249, Bug #27389894)

* NDB Client Programs: ndb_top did not support a number of
options common to most NDB programs. The following
options are now supported:

+ --defaults-file

+ --defaults-extra-file

+ --print-defaults

+ --no-defaults

+ --defaults-group-suffix
In addition, ndb_top now supports a --socket option
(short form -S) for specifying a socket file to use for
the connection. (Bug #86614, Bug #26236298)

* MySQL NDB ClusterJ: ClusterJ quit unexpectedly as there
was no error handling in the scanIndex() function of the
ClusterTransactionImpl class for a null returned to it
internally by the scanIndex() method of the
ndbTransaction class. (Bug #27297681, Bug #88989)

* In some circumstances, when a transaction was aborted in
the DBTC block, there remained links to trigger records
from operation records which were not yet
reference-counted, but when such an operation record was
released the trigger reference count was still
decremented. (Bug #27629680)

* An NDB online backup consists of data, which is fuzzy,
and a redo and undo log. To restore to a consistent state
it is necessary to ensure that the log contains all of
the changes spanning the capture of the fuzzy data
portion and beyond to a consistent snapshot point. This
is achieved by waiting for a GCI boundary to be passed
after the capture of data is complete, but before
stopping change logging and recording the stop GCI in the
backup's metadata.
At restore time, the log is replayed up to the stop GCI,
restoring the system to the state it had at the
consistent stop GCI. A problem arose when, under load, it
was possible to select a GCI boundary which occurred too
early and did not span all the data captured. This could
lead to inconsistencies when restoring the backup; these
could be be noticed as broken constraints or corrupted
BLOB entries.
Now the stop GCI is chosen is so that it spans the entire
duration of the fuzzy data capture process, so that the
backup log always contains all data within a given stop
GCI. (Bug #27497461)
References: See also: Bug #27566346.

* For NDB tables, when a foreign key was added or dropped
as a part of a DDL statement, the foreign key metatdata
for all parent tables referenced should be reloaded in
the handler on all SQL nodes connected to the cluster,
but this was done only on the mysqld on which the
statement was executed. Due to this, any subsequent
queries relying on foreign key metadata from the
corresponding parent tables could return inconsistent
results. (Bug #27439587)
References: See also: Bug #82989, Bug #24666177.

* ANALYZE TABLE used excessive amounts of CPU on large,
low-cardinality tables. (Bug #27438963)

* Queries using very large lists with IN were not handled
correctly, which could lead to data node failures.
(Bug #27397802)

* A data node overload could in some situations lead to an
unplanned shutdown of the data node, which led to all
data nodes disconnecting from the management and nodes.
This was due to a situation in which API_FAILREQ was not
the last received signal prior to the node failure.
As part of this fix, the transaction coordinator's
handling of SCAN_TABREQ signals for an ApiConnectRecord
in an incorrect state was also improved. (Bug #27381901)
References: See also: Bug #47039, Bug #11755287.

* In a two-node cluster, when the node having the lowest ID
was started using --nostart, API clients could not
connect, failing with Could not alloc node id at HOST
port PORT_NO: No free node id found for mysqld(API).
(Bug #27225212)

* Changing MaxNoOfExecutionThreads without an initial
system restart led to an unplanned data node shutdown.
(Bug #27169282)
References: This issue is a regression of: Bug #26908347,
Bug #26968613.

* Race conditions sometimes occurred during asynchronous
disconnection and reconnection of the transporter while
other threads concurrently inserted signal data into the
send buffers, leading to an unplanned shutdown of the
As part of the work fixing this issue, the internal
templating function used by the Transporter Registry when
it prepares a send is refactored to use
likely-or-unlikely logic to speed up execution, and to
remove a number of duplicate checks for NULL.
(Bug #24444908, Bug #25128512)
References: See also: Bug #20112700.

* ndb_restore sometimes logged data file and log file
progress values much greater than 100%. (Bug #20989106)

* The internal function BitmaskImpl::setRange() set one bit
fewer than specified. (Bug #90648, Bug #27931995)

* It was not possible to create an NDB table using
FOR_RA_BY_LDM_X_3, or FOR_RA_BY_LDM_X_4. (Bug #89811, Bug
References: This issue is a regression of: Bug #81759,
Bug #23544301.

* Adding a [tcp] or [shm] section to the global
configuration file for a cluster with multiple data nodes
caused default TCP connections to be lost to the node
using the single section. (Bug #89627, Bug #27532407)

* As a result of the reuse of code intended for send
threads when performing an assist send, all of the local
release send buffers were released to the global pool,
which caused the intended level of the local send buffer
pool to be ignored. Now send threads and assisting worker
threads follow their own policies for maintaining their
local buffer pools. (Bug #89119, Bug #27349118)

* When sending priority A signals, we now ensure that the
number of pending signals is explicitly initialized.
(Bug #88986, Bug #27294856)

* In a MySQL Cluster with one MySQL Server configured to
write a binary log failure occurred when creating and
using an NDB table with non-stored generated columns. The
problem arose only when the product was built with
debugging support. (Bug #86084, Bug #25957586)

* ndb_restore --print_data --hex did not print trailing 0s
of LONGVARBINARY values. (Bug #65560, Bug #14198580)

* When the internal function
ha_ndbcluster::copy_fk_for_offline_alter() checked
dependent objects on a table from which it was supposed
to drop a foreign key, it did not perform any filtering
for foreign keys, making it possible for it to attempt
retrieval of an index or trigger instead, leading to a
spurious Error 723 (No such table).

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

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Written By
MySQL Cluster 7.6.6 GA has been released
June 01, 2018 06:48AM

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