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 7.6.9 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.
MySQL Cluster 7.6 is also available from our repository for Linux
platforms, go here for details:
http://dev.mysql.com/downloads/repo/
The release notes are available from
http://dev.mysql.com/doc/relnotes/mysql-cluster/7.6/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 7.6.9 (5.7.25-ndb-7.6.9) (2019-01-22,
General Availability)
MySQL NDB Cluster 7.6.9 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
https://dev.mysql.com/downloads/cluster/.
For an overview of changes made in NDB Cluster 7.6, see What
is New in NDB Cluster 7.6
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-what-is-new-7-6.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 5.7
through MySQL 5.7.25 (see Changes in MySQL 5.7.25
(2019-01-21, General Availability)
(http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-25.html)).
Bugs Fixed
* Important Change: When restoring to a cluster using data
node IDs different from those in the original cluster,
ndb_restore tried to open files corresponding to node ID
0. To keep this from happening, the --nodeid and
--backupid options---neither of which has a default
value---are both now explicitly required when invoking
ndb_restore. (Bug #28813708)
* Packaging; MySQL NDB ClusterJ: libndbclient was missing
from builds on some platforms. (Bug #28997603)
* NDB Replication: A DROP DATABASE operation involving
certain very large tables could lead to an unplanned
shutdown of the cluster. (Bug #28855062)
* NDB Replication: When writes on the master---done in such
a way that multiple changes affecting BLOB column values
belonging to the same primary key were part of the same
epoch---were replicated to the slave, Error 1022 occurred
due to constraint violations in the NDB$BLOB_id_part
table. (Bug #28746560)
* NDB Cluster APIs: When the NDB kernel's SUMA block sends
a TE_ALTER event, it does not keep track of when all
fragments of the event are sent. When NDB receives the
event, it buffers the fragments, and processes the event
when all fragments have arrived. An issue could possibly
arise for very large table definitions, when the time
between transmission and reception could span multiple
epochs; during this time, SUMA could send a
SUB_GCP_COMPLETE_REP signal to indicate that it has sent
all data for an epoch, even though in this case that is
not entirely true since there may be fragments of a
TE_ALTER event still waiting on the data node to be sent.
Reception of the SUB_GCP_COMPLETE_REP leads to closing
the buffers for that epoch. Thus, when TE_ALTER finally
arrives, NDB assumes that it is a duplicate from an
earlier epoch, and silently discards it.
We fix the problem by making sure that the SUMA kernel
block never sends a SUB_GCP_COMPLETE_REP for any epoch in
which there are unsent fragments for a SUB_TABLE_DATA
signal.
This issue could have an impact on NDB API applications
making use of TE_ALTER events. (SQL nodes do not make any
use of TE_ALTER events and so they and applications using
them were not affected.) (Bug #28836474)
* Where a data node was restarted after a configuration
change whose result was a decrease in the sum of
MaxNoOfTables, MaxNoOfOrderedIndexes, and
MaxNoOfUniqueHashIndexes, it sometimes failed with a
misleading error message which suggested both a temporary
error and a bug, neither of which was the case.
The failure itself is expected, being due to the fact
that there is at least one table object with an ID
greater than the (new) sum of the parameters just
mentioned, and that this table cannot be restored since
the maximum value for the ID allowed is limited by that
sum. The error message has been changed to reflect this,
and now indicates that this is a permanent error due to a
problem configuration. (Bug #28884880)
* When only the management server but no data nodes were
started, RESTART ALL timed out and eventually failed.
This was because, as part of a restart, ndb_mgmd starts a
timer, sends a STOP_REQ signal to all the data nodes, and
waits for all of them to reach node state SL_CMVMI. The
issue arose becaue no STOP_REQ signals were ever sent,
and thus no data nodes reached SL_CMVMI. This meant that
the timer always expired, causing the restart to fail.
(Bug #28728485, Bug #28698831)
References: See also: Bug #11757421.
* Running ANALYZE TABLE on an NDB table with an index
having longer than the supported maximum length caused
data nodes to fail. (Bug #28714864)
* It was possible in certain cases for nodes to hang during
an initial restart. (Bug #28698831)
References: See also: Bug #27622643.
* The output of ndb_config --configinfo --xml --query-all
now shows that configuration changes for the ThreadConfig
and MaxNoOfExecutionThreads data node parameters require
system initial restarts (restart="system"
initial="true"). (Bug #28494286)
* API nodes should observe that a node is moving through
SL_STOPPING phases (graceful stop) and stop using the
node for new transactions, which minimizes potential
disruption in the later phases of the node shutdown
process. API nodes were only informed of node state
changes via periodic heartbeat signals, and so might not
be able to avoid interacting with the node shutting down.
This generated unnecessary failures when the heartbeat
interval was long. Now when a data node is being
gracefully stopped, all API nodes are notified directly,
allowing them to experience minimal disruption. (Bug
#28380808)
* Executing SELECT * FROM INFORMATION_SCHEMA.TABLES caused
SQL nodes to restart in some cases. (Bug #27613173)
* When scanning a row using a TUP scan or ACC scan, or when
performing a read using the primary key, it is possible
to start a read of the row and hit a real-time break
during which it is necessary to wait for the page to
become available in memory. When the page request returns
later, an attempt to read the row fails due to an invalid
checksum; this is because, when the row is deleted, its
checksum is invalidated.
This problem is solved by introducing a new tuple header
DELETE_WAIT flag, which is checked before starting any
row scan or PK read operations on the row where disk data
pages are not yet available, and cleared when the row is
finally committed. (Bug #27584165)
References: See also: Bug #28868412.
* When running a cluster with 4 or more data nodes under
very high loads, data nodes could sometimes fail with
Error 899 Rowid already allocated. (Bug #25960230)
* mysqld shut down unexpectedly when a purge of the binary
log was requested before the server had completely
started, and it was thus not yet ready to delete rows
from the ndb_binlog_index table. Now when this occurs,
requests for any needed purges of the ndb_binlog_index
table are saved in a queue and held for execution when
the server has completely started. (Bug #25817834)
* When starting, a data node copies metadata, while a local
checkpoint updates metadata. To avoid any conflict, any
ongoing LCP activity is paused while metadata is being
copied. An issue arose when a local checkpoint was paused
on a given node, and another node that was also
restarting checked for a complete LCP on this node; the
check actually caused the LCP to be completed before
copying of metadata was complete and so ended the pause
prematurely. Now in such cases, the LCP completion check
waits to complete a paused LCP until copying of metadata
is finished and the pause ends as expected, within the
LCP in which it began. (Bug #24827685)
* Asynchronous disconnection of mysqld from the cluster
caused any subsequent attempt to start an NDB API
transaction to fail. If this occurred during a bulk
delete operation, the SQL layer called
HA::end_bulk_delete(), whose implementation by
ha_ndbcluster assumed that a transaction had been
started, and could fail if this was not the case. This
problem is fixed by checking that the transaction pointer
used by this method is set before referencing it. (Bug
#20116393)
* NdbScanFilter did not always handle NULL according to the
SQL standard, which could result in sending
non-qualifying rows to be filtered (otherwise not
necessary) by the MySQL server. (Bug #92407, Bug
#28643463)
* NDB attempted to use condition pushdown on greater-than
(>) and less-than (<) comparisons with ENUM column values
but this could cause rows to be omitted in the result.
Now such comparisons are no longer pushed down.
Comparisons for equality (=) and inequality (<> / !=)
with ENUM values are not affected by this change, and
conditions including these comparisons can still be
pushed down. (Bug #92321, Bug #28610217)
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