Dear MySQL Users,
MySQL Cluster is the distributed, shared-nothing variant of MySQL.
This storage engine provides:
- In-memory persistent storage - Real-time performance
- 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 7.4 makes significant advances in performance;
operational efficiency (such as enhanced reporting and faster restarts
and upgrades) and conflict detection and resolution for active-active
replication between MySQL Clusters.
MySQL Cluster 7.4.9, 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/7.4/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 7.4.9 (5.6.28-ndb-7.4.9) (2016-01-18)
MySQL Cluster NDB 7.4.9 is a new release of MySQL Cluster
7.4, based on MySQL Server 5.6 and including features in
version 7.4 of the NDB storage engine, as well as fixing
recently discovered bugs in previous MySQL Cluster releases.
Obtaining MySQL Cluster NDB 7.4. MySQL Cluster NDB 7.4
source code and binaries can be obtained from
http://dev.mysql.com/downloads/cluster/.
For an overview of changes made in MySQL Cluster NDB 7.4, see
MySQL Cluster Development in MySQL Cluster NDB 7.4
(http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-development-
5-6-ndb-7-4.html).
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 5.6
through MySQL 5.6.28 (see Changes in MySQL 5.6.28
(2015-12-07)
(http://dev.mysql.com/doc/relnotes/mysql/5.6/en/news-5-6-28.html)).
Functionality Added or Changed
* Important Change: Previously, the NDB scheduler always
optimized for speed against throughput in a predetermined
manner (this was hard coded); this balance can now be set
using the SchedulerResponsiveness data node configuration
parameter. This parameter accepts an integer in the range
of 0-10 inclusive, with 5 as the default. Higher values
provide better response times relative to throughput.
Lower values provide increased throughput, but impose
longer response times. (Bug #78531, Bug #21889312)
* Added the tc_time_track_stats table to the ndbinfo
information database. This table provides time-tracking
information relating to transactions, key operations, and
scan operations performed by NDB. (Bug #78533, Bug
#21889652)
* Cluster Replication: Normally, RESET SLAVE causes all
entries to be deleted from the mysql.ndb_apply_status
table. This release adds the ndb_clear_apply_status
system variable, which makes it possible to override this
behavior. This variable is ON by default; setting it to
OFF keeps RESET SLAVE from purging the ndb_apply_status
table. (Bug #12630403)
Bugs Fixed
* Important Change: Users can now set the number and length
of connection timeouts allowed by most NDB programs with
the --connect-retries and --connect-retry-delay command
line options introduced for the programs in this release.
For ndb_mgm, --connect-retries supersedes the existing
--try-reconnect option. (Bug #57576, Bug #11764714)
* 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)
* Attempting to create an NDB table having greater than the
maximum supported combined width for all BIT columns
(4096) caused data node failure when these columns were
defined with COLUMN_FORMAT DYNAMIC. (Bug #21889267)
* Creating a table with the maxmimum supported number of
columns (512) all using COLUMN_FORMAT DYNAMIC led to data
node failures. (Bug #21863798)
* In certain cases, a cluster failure (error 4009) was
reported as Unknown error code. (Bug #21837074)
* For a timeout in GET_TABINFOREQ while executing a CREATE
INDEX statement, mysqld returned Error 4243 (Index not
found) instead of the expected Error 4008 (Receive from
NDB failed).
The fix for this bug also fixes similar timeout issues
for a number of other signals that are sent the DBDICT
kernel block as part of DDL operations, including
ALTER_TAB_REQ, CREATE_INDX_REQ, DROP_FK_REQ,
DROP_INDX_REQ, INDEX_STAT_REQ, DROP_FILE_REQ,
CREATE_FILEGROUP_REQ, DROP_FILEGROUP_REQ, CREATE_EVENT,
WAIT_GCP_REQ, DROP_TAB_REQ, and LIST_TABLES_REQ, as well
as several internal functions used in handling NDB schema
operations. (Bug #21277472)
References: See also Bug #20617891, Bug #20368354, Bug
#19821115.
* 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)
* Compilation of MySQL Cluster failed on SUSE Linux
Enterprise Server 12. (Bug #79429, Bug #22292329)
* 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)
* When executed on an NDB table, ALTER TABLE ... DROP INDEX
made changes to an internal array referencing the indexes
before the index was actually dropped, and did not revert
these changes in the event that the drop was not
completed. One effect of this was that, after attempting
to drop an index on which there was a foreign key
dependency, the expected error referred to the wrong
index, and subsequent attempts using SQL to modify
indexes of this table failed. (Bug #78980, Bug #22104597)
* 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)
* ndbmtd checked for signals being sent only after a full
cycle in run_job_buffers, which is performed for all job
buffer inputs. Now this is done as part of
run_job_buffers itself, avoiding executing for extended
periods without sending to other nodes or flushing signals
to other threads. (Bug #78530, Bug #21889088)
* In MySQL Cluster 7.4 scan executions was optimised by
handling multiple rows at a time. This has two effects,
1) it gives scans higher prio compared to key lookup
operations, 2) it changes the behaviour of the scheduler.
2) was fixed, restoring the former scheduling behaviour.
1) is kept since it has a significant performance benefit
but means were provided for change of this in exceptional
circumstances. (Bug #78526, Bug #21886644)
* Disk Data: A unique index on a column of an NDB table is
implemented with an associated internal ordered index,
used for scanning. While dropping an index, this ordered
index was dropped first, followed by the drop of the
unique index itself. This meant that, when the drop was
rejected due to (for example) a constraint violation, the
statement was rejected but the associated ordered index
remained deleted, so that any subsequent operation using
a scan on this table failed. We fix this problem by
causing the unique index to be removed first, before
removing the ordered index; removal of the related
ordered index is no longer performed when removal of a
unique index fails. (Bug #78306, Bug #21777589)
* 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)
* Cluster API: Garbage collection is performed on several
objects in the implementation of NdbEventOperation, based
on which GCIs have been consumed by clients, including
those that have been dropped by
Ndb::dropEventOperation(). In this implementation, the
assumption was made that the global checkpoint index
(GCI) is always monotonically increasing, although this
is not the case during an initial restart, when the GCI
is reset. This could lead to event objects in the NDB API
being released prematurely or not at all, in the latter
case causing a resource leak.
To prevent this from happening, the NDB event object's
implementation now tracks, internally, both the GCI and
the generation of the GCI; the generation is incremented
whenever the node process is restarted, and this value is
now used to provide a monotonically increasing sequence.
(Bug #73781, Bug #21809959)
On behalf of the MySQL Release Team,
Lars Tangvald
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MySQL Cluster 7.4.9 has been released (no replies)
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