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 and Memcached)

MySQL Cluster 7.2.23, 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/7.2/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 Cluster NDB 7.2.23 (5.5.47-ndb-7.2.23) (2016-01-19)

MySQL Cluster NDB 7.2.23 is a new release of MySQL Cluster,
incorporating new features in the NDB storage engine, and
fixing recently discovered bugs in previous MySQL Cluster NDB
7.2 development releases.

Obtaining MySQL Cluster NDB 7.2. MySQL Cluster NDB 7.2
source code and binaries can be obtained from
http://dev.mysql.com/downloads/cluster/.

This release also incorporates all bugfixes and changes made
in previous MySQL Cluster releases, as well as all bugfixes
and feature changes which were added in mainline MySQL 5.5
through MySQL 5.5.47 (see Changes in MySQL 5.5.47
(2015-12-07)
(http://dev.mysql.com/doc/relnotes/mysql/5.5/en/news-5-5-47.html)).

Bugs Fixed

* In debug builds, a WAIT_EVENT while polling caused
excessive logging to stdout. (Bug #22203672)

* When executing a schema operation such as CREATE TABLE on
a MySQL Cluster with multiple SQL nodes, it was possible
for the SQL node on which the operation was performed to
time out while waiting for an acknowledgement from the
others. This could occur when different SQL nodes had
different settings for --ndb-log-updated-only,
--ndb-log-update-as-write, or other mysqld options
effecting binary logging by NDB.
This happened due to the fact that, in order to
distribute schema changes between them, all SQL nodes
subscribe to changes in the ndb_schema system table, and
that all SQL nodes are made aware of each others
subscriptions by subscribing to TE_SUBSCRIBE and
TE_UNSUBSCRIBE events. The names of events to subscribe
to are constructed from the table names, adding REPL$ or
REPLF$ as a prefix. REPLF$ is used when full binary
logging is specified for the table. The issue described
previously arose because different values for the options
mentioned could lead to different events being subscribed
to by different SQL nodes, meaning that all SQL nodes
were not necessarily aware of each other, so that the
code that handled waiting for schema distribution to
complete did not work as designed.
To fix this issue, MySQL Cluster now treats the
ndb_schema table as a special case and enforces full
binary logging at all times for this table, independent
of any settings for mysqld binary logging options. (Bug
#22174287, Bug #79188)

* Using ndb_mgm STOP -f to force a node shutdown even when
it triggered a complete shutdown of the cluster, it was
possible to lose data when a sufficient number of nodes
were shut down, triggering a cluster shutodwn, and the
timing was such that SUMA handovers had been made to
nodes already in the process of shutting down. (Bug
#17772138)

* The internal NdbEventBuffer::set_total_buckets() method
calculated the number of remaining buckets incorrectly.
This caused any incomplete epoch to be prematurely
completed when the SUB_START_CONF signal arrived out of
order. Any events belonging to this epoch arriving later
were then ignored, and so effectively lost, which
resulted in schema changes not being distributed
correctly among SQL nodes. (Bug #79635, Bug #22363510)

* Schema events were appended to the binary log out of
order relative to non-schema events. This was caused by
the fact that the binlog injector did not properly handle
the case where schema events and non-schema events were
from different epochs.
This fix modifies the handling of events from the two
schema and non-schema event streams such that events are
now always handled one epoch at a time, starting with
events from the oldest available epoch, without regard to
the event stream in which they occur. (Bug #79077, Bug
#22135584, Bug #20456664)

* NDB failed during a node restart due to the status of the
current local checkpoint being set but not as active,
even though it could have other states under such
conditions. (Bug #78780, Bug #21973758)

* Cluster Replication: While the binary log injector thread
was handling failure events, it was possible for all NDB
tables to be left indefinitely in read-only mode. This
was due to a race condition between the binlog injector
thread and the utility thread handling events on the
ndb_schema table, and to the fact that, when handling
failure events, the binlog injector thread places all NDB
tables in read-only mode until all such events are
handled and the thread restarts itself.
When the binlog inject thread receives a group of one or
more failure events, it drops all other existing event
operations and expects no more events from the utility
thread until it has handled all of the failure events and
then restarted itself. However, it was possible for the
utility thread to continue attempting binary log setup
while the injector thread was handling failures and thus
attempting to create the schema distribution tables as
well as event subscriptions on these tables. If the
creation of these tables and event subscriptions occurred
during this time, the binlog injector thread's
expectation that there were no further event operations
was never met; thus, the injector thread never restarted,
and NDB tables remained in read-only as described
previously.
To fix this problem, the Ndb object that handles schema
events is now definitely dropped once the ndb_schema
table drop event is handled, so that the utility thread
cannot create any new events until after the injector
thread has restarted, at which time, a new Ndb object for
handling schema events is created. (Bug #17674771, Bug
#19537961, Bug #22204186, Bug #22361695)

* Cluster API: The binlog injector did not work correctly
with TE_INCONSISTENT event type handling by
Ndb::nextEvent(). (Bug #22135541)
References: See also Bug #20646496.

* Cluster API: Ndb::pollEvents() and pollEvents2() were
slow to receive events, being dependent on other client
threads or blocks to perform polling of transporters on
their behalf. This fix allows a client thread to perform
its own transporter polling when it has to wait in either
of these methods.
Introduction of transporter polling also revealed a
problem with missing mutex protection in the
ndbcluster_binlog handler, which has been added as part
of this fix. (Bug #20957068, Bug #22224571, Bug #79311)

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