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 7.5.7, 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 7.5 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/7.5/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 7.5.7 (5.7.19-ndb-7.5.7) (2017-07-19,
General Availability)

MySQL NDB Cluster 7.5.7 is a new release of MySQL NDB Cluster
7.5, based on MySQL Server 5.7 and including features in
version 7.5 of the NDB
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster.html)
storage engine, as well as fixing recently discovered bugs in
previous NDB Cluster releases.

Obtaining MySQL NDB Cluster 7.5. MySQL NDB Cluster 7.5
source code and binaries can be obtained from
g://dev.mysql.com/downloads/cluster/.

For an overview of changes made in MySQL NDB Cluster 7.5, see
What is New in NDB Cluster 7.5
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-what-is-new-7-5.html).

This release also incorporates all bugfixes and changes made
in previous NDB Cluster releases, as well as all bugfixes and
feature changes which were added in mainline MySQL 5.7
through MySQL 5.7.19 (see Changes in MySQL 5.7.19
(2017-07-17, General Availability)
(http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-19.html)).

* Packaging Notes

* Functionality Added or Changed

* Bugs Fixed

Packaging Notes

* mysqladmin was added to Docker/Minimal packages because
it is needed by InnoDB Cluster. (Bug #25998285)

Functionality Added or Changed

* Important Change; MySQL NDB ClusterJ: The ClusterJPA
plugin for OpenJPA is no longer supported by NDB Cluster,
and has been removed from the distribution. (Bug
#23563810)

* NDB Replication: Added the --ndb-log-update-minimal
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-minimal)
option for logging by mysqld. This option causes only
primary key values to be written in the before image, and
only changed columns in the after image. (Bug #24438868)

* NDB Cluster APIs; ndbinfo Information Database: Added two
tables to the ndbinfo
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo.html)
information database. The config_nodes
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-config-nodes.html)
table provides information about
nodes that are configured as part of a given NDB Cluster,
such as node ID and process type. The processes
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-processes.html)
table shows information about nodes
currently connected to the cluster; this information
includes the process name and system process ID, and
service address. For each data node and SQL node, it also
shows the process ID of the node's angel process.
As part of the work done to implement the processes
table, a new set_service_uri()
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection-set-service-uri.html)
method has been added to the NDB API.
For more information, see The ndbinfo config_nodes Table
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-config-nodes.html),
and The ndbinfo processes Table
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-processes.html),
as well as Ndb_cluster_connection::set_service_uri()
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection-set-service-uri.html).

* NDB Cluster APIs: The system name of an NDB cluster is
now visible in the mysql client as the value of the
Ndb_system_name
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-options-variables.html#statvar_Ndb_system_name)
status variable, and can also be obtained by NDB API application
using the Ndb_cluster_connection::get_system_name()
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection-get-system-name.html)
method. The system name can be set using the Name parameter in
the [system] section of the cluster configuration file.

* MySQL NDB ClusterJ: A new automatic reconnection feature
has been implemented to facilitate the handling of
connectivity issues. The feature is enabled by setting a
positive number for a new connection property,
com.mysql.clusterj.connection.autoreconnect.timeout,
which specifies the length of the timeout period in
seconds. If a connectivity error occurs, ClusterJ
attempts to reconnect the application to the NDB Cluster
after the application closes all the sessions; if the
application does not close all sessions within the
timeout period, ClusterJ closes any open sections
forcibly, and then attempts reconnection. See Error
Handling and Reconnection
(http://dev.mysql.com/doc/ndbapi/en/mccj-using-clusterj-start.html#mccj-using-clusterj-reconnect)
for details.

* Added the --diff-default
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-config.html#option_ndb_config_diff-default)
option for ndb_config. This option causes the program to
print only those parameters having values that differ
from their defaults. (Bug #85831, Bug #25844166)

* Added the --query-all
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-config.html#option_ndb_config_query-all)
option to ndb_config. This option acts much like the --query
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-config.html#option_ndb_config_query)
option except that --query-all (short form: -a) dumps
configuration information for all attributes at one time.
(Bug #60095, Bug #11766869)

Bugs Fixed

* Packaging: Two missing dependencies were added to the apt
packages:

+ The data node package requires
libclass-methodmaker-perl

+ The auto-installer requires python-paramiko
(Bug #85679, Bug #25799465)

* Solaris; ndbmemcache: ndbmemcache was not built correctly
on Solaris platforms when compiling NDB Cluster using
Developer Studio. (Bug #85477, Bug #25730703)

* Solaris; MySQL NDB ClusterJ: ClusterJ was not built
correctly on Solaris platforms when compiling NDB Cluster
using Oracle Developer Studio. (Bug #25738510)

* NDB Replication: Added a check to stop an NDB replication
slave when configuration as a multi-threaded slave is
detected (for example, if slave_parallel_workers
(http://dev.mysql.com/doc/refman/5.7/en/replication-options-slave.html#sysvar_slave_parallel_workers)
is set to a nonzero value). (Bug #21074209)

* NDB Replication: Execution of CREATE TABLE
(http://dev.mysql.com/doc/refman/5.7/en/create-table.html)
could in some cases cause the replication slave SQL
thread to hang. (Bug #85015, Bug #25654833)
References: This issue is a regression of: Bug #83676,
Bug #25042101.

* NDB Cluster APIs: The implementation method
NdbDictionary::NdbTableImpl::getColumn(), used from many
places in the NDB API where a column is referenced by
name, has been made more efficient. This method used a
linear search of an array of columns to find the correct
column object, which could be inefficient for tables with
many columns, and was detected as a significant use of
CPU in customer applications. (Ideally, users should
perform name-to-column object mapping, and then use
column IDs or objects in method calls, but in practice
this is not always done.) A less costly hash index
implementation, used previously for the name lookup, is
reinstated for tables having relatively many columns. (A
linear search continues to be used for tables having
fewer columns, where the difference in performance is
neglible.) (Bug #24829435)

* MySQL NDB ClusterJ: The JTie and NDB JTie tests were
skipped when the unit tests for ClusterJ were being run.
(Bug #26088583)

* Backup .log files contained log entries for one or more
extra fragments, due to an issue with filtering out
changes logged by other nodes in the same node group.
This resulted in a larger .log file and thus use of more
resources than necessary; it could also cause problems
when restoring, since backups from different nodes could
interfere with one another while the log was being
applied. (Bug #25891014)

* When making the final write to a redo log file, it is
expected that the next log file is already opened for
writes, but this was not always the case with a slow
disk, leading to node failure. Now in such cases NDB
waits for the next file to be opened properly before
attempting to write to it. (Bug #25806659)

* Data node threads can be bound to a single CPU or a set
of CPUs, a set of CPUs being represented internally by
NDB as a SparseBitmask. When attempting to lock to a set
of CPUs, CPU usage was excessive due to the fact that the
routine performing the locks used the
mt_thr_config.cpp::do_bind() method, which looks for bits
that are set over the entire theoretical range of the
SparseBitmask (2^32-2, or 4294967294). This is fixed by
using SparseBitmask::getBitNo(), which can be used to
iterate over only those bits that are actually set,
instead. (Bug #25799506)

* When ndb_report_thresh_binlog_epoch_slip
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-options-variables.html#sysvar_ndb_report_thresh_binlog_epoch_slip)
was enabled, an event buffer status message with
report_reason=LOW/ENOUGH_FREE_EVENTBUFFER was printed in
the logs when event buffer usage was high and then
decreased to a lower level. This calculation was based on
total allocated event buffer memory rather than the limit
set by ndb_eventbuffer_max_alloc
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-options-variables.html#sysvar_ndb_eventbuffer_max_alloc);
it was also printed even when the event buffer had unlimited
memory (ndb_eventbuffer_max_alloc = 0, the default),
which could confuse users.
This is fixed as follows:

+ The calculation of ndb_eventbuffer_free_percent
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-options-variables.html#sysvar_ndb_eventbuffer_free_percent)
is now based on ndb_eventbuffer_max_alloc,
rather than the amount actually allocated.

+ When ndb_eventbuffer_free_percent is set and
ndb_eventbuffer_max_alloc is equal to 0, event
buffer status messages using
report_reason=LOW/ENOUGH_FREE_EVENTBUFFER are no
longer printed.

+ When ndb_report_thresh_binlog_epoch_slip is set, an
event buffer status message showing
report_reason=BUFFERED_EPOCHS_OVER_THRESHOLD is
written each 10 seconds (rather than every second)
whenever this is greater than the threshold.
(Bug #25726723)

* A bulk update is executed by reading records and
executing a transaction on the set of records, which is
started while reading them. When transaction
initialization failed, the transaction executor function
was subsequently unaware that this had occurred, leading
to SQL node failures. This issue is fixed by providing
appropriate error handling when attempting to initialize
the transaction. (Bug #25476474)
References: See also: Bug #20092754.

* Setting NoOfFragmentLogParts such that there were more
than 4 redo log parts per local data manager led to
resource exhaustion and subsequent multiple data node
failures. Since this is an invalid configuration, a check
has been added to detect a configuration with more than 4
redo log parts per LDM, and reject it as invalid. (Bug
#25333414)

* Execution of an online ALTER TABLE ... REORGANIZE
PARTITION
(http://dev.mysql.com/doc/refman/5.7/en/alter-table-online-operations.html)
statement on an NDB table having a
primary key whose length was greater than 80 bytes led to
restarting of data nodes, causing the reorganization to
fail. (Bug #25152165)

* In certain cases, a failed ALTER TABLE ... ADD UNIQUE KEY
(http://dev.mysql.com/doc/refman/5.7/en/alter-table.html)
statement could lead to SQL node failure. (Bug #24444878)
References: This issue is a regression of: Bug #23089566.

* Error 240 is raised when there is a mismatch between
foreign key trigger columns and the values supplied to
them during trigger execution, but had no error message
indicating the source of the problem. (Bug #23141739)
References: See also: Bug #23068914, Bug #85857.

* If the number of LDM blocks was not evenly divisible by
the number of TC/SPJ blocks, SPJ requests were not
equally distributed over the available SPJ instances. Now
a round-robin distribution is used to distribute SPJ
requests across all available SPJ instances more
effectively.
As part of this work, a number of unused member variables
have been removed from the class Dbtc. (Bug #22627519)

* ALTER TABLE .. MAX_ROWS=0
(http://dev.mysql.com/doc/refman/5.7/en/alter-table.html)
can now be performed only by using a copying ALTER TABLE
statement. Resetting MAX_ROWS to 0 can no longer be
performed using ALGORITHM=INPLACE. (Bug #21960004)

* During a system restart, when a node failed due to having
missed sending heartbeats, all other nodes reported only
that another node had failed without any additional
information. Now in such cases, the fact that heartbeats
were missed and the ID of the node that failed to send
heartbeats is reported in both the error log and the data
node log. (Bug #21576576)

* The planned shutdown of an NDB Cluster having more than
10 data nodes was not always performed gracefully. (Bug
#20607730)

* Due to a previous issue with unclear separation between
the optimize and execute phases when a query involved a
GROUP BY, the join-pushable evaluator was not sure
whether its optimized query execution plan was in fact
pushable. For this reason, such grouped joins were always
considered not pushable. It has been determined that the
separation issue has been resolved by work already done
in MySQL 5.6, and so we now remove this limitation. (Bug
#86623, Bug #26239591)

* When deleting all rows from a table immediately followed
by DROP TABLE
(http://dev.mysql.com/doc/refman/5.7/en/drop-table.html),
it was possible that the shrinking of the DBACC hash
index was not ready prior to the drop. This shrinking is
a per-fragment operation that does not check the state of
the table. When a table is dropped, DBACC releases
resources, during which the description of the fragment
size and page directory is not consistent; this could
lead to reads of stale pages, and undefined behavior.
Inserting a great many rows followed by dropping the
table should also have had such effects due to expansion
of the hash index.
To fix this problem we make sure, when a fragment is
about to be released, that there are no pending expansion
or shrinkage operations on this fragment. (Bug #86449,
Bug #26138592)

* The internal function execute_signals() in mt.cpp read
three section pointers from the signal even when none was
passed to it. This was mostly harmless, although
unneeded. When the signal read was the last one on the
last page in the job buffer, and the next page in memory
was not mapped or otherwise accessible, ndbmtd failed
with an error. To keep this from occurring, this function
now only reads section pointers that are actually passed
to it. (Bug #86354, Bug #26092639)

* The ndb_show_tables program --unqualified
(http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-show-tables.html#option_ndb_show_tables_unqualified)
option did not work correctly when set to 0
(false); this should disable the option and so cause
fully qualified table and index names to be printed in
the output. (Bug #86017, Bug #25923164)

* When an NDB table with foreign key constraints is
created, its indexes are created first, and then, during
foreign key creation, these indexes are loaded into the
NDB dictionary cache. When a CREATE TABLE
(http://dev.mysql.com/doc/refman/5.7/en/create-table.html)
statement failed due to an issue relating to foreign
keys, the indexes already in the cache were not
invalidated. This meant that any subsequent CREATE TABLE
with any indexes having the same names as those in the
failed statement produced inconsistent results. Now, in
such cases, any indexes named in the failed CREATE TABLE
are immediately invalidated from the cache. (Bug #85917,
Bug #25882950)

* Attempting to execute ALTER TABLE ... ADD FOREIGN KEY
(http://dev.mysql.com/doc/refman/5.7/en/alter-table.html)
when the key to be added had the name of an existing
foreign key on the same table failed with the wrong error
message. (Bug #85857, Bug #23068914)

* The node internal scheduler (in mt.cpp) collects
statistics about its own progress and any outstanding
work it is performing. One such statistic is the number
of outstanding send bytes, collected in
send_buffer::m_node_total_send_buffer_size. This
information may later be used by the send thread
scheduler, which uses it as a metric to tune its own send
performance versus latency.
In order to reduce lock contention on the internal send
buffers, they are split into two thr_send_buffer parts,
m_buffer and m_sending, each protected by its own mutex,
and their combined size repesented by
m_node_total_send_buffer_size.
Investigation of the code revealed that there was no
consistency as to which mutex was used to update
m_node_total_send_buffer_size, with the result that there
was no consurrency protection for this value. To avoid
this, m_node_total_send_buffer_size is replaced with two
values, m_buffered_size and m_sending_size, which keep
separate track of the sizes of the two buffers. These
counters are updated under the protection of two
different mutexes protecting each buffer individually,
and are now added together to obtain the total size.
With concurrency control established, updates of the
partial counts should now be correct, so that their
combined value no longer accumulates errors over time.
(Bug #85687, Bug #25800933)

* Dropped TRANS_AI signals that used the long signal format
were not handled by the DBTC kernel block. (Bug #85606,
Bug #25777337)
References: See also: Bug #85519, Bug #27540805.

* To prevent a scan from returning more rows, bytes, or
both than the client has reserved buffers for, the DBTUP
kernel block reports the size of the TRANSID_AI it has
sent to the client in the TUPKEYCONF signal it sends to
the requesting DBLQH block. DBLQH is aware of the maximum
batch size available for the result set, and terminates
the scan batch if this has been exceeded.
The DBSPJ block's FLUSH_AI attribute allows DBTUP to
produce two TRANSID_AI results from the same row, one for
the client, and one for DBSPJ, which is needed for key
lookups on the joined tables. The size of both of these
were added to the read length reported by the DBTUP
block, which caused the controlling DBLQH block to
believe that it had consumed more of the available
maximum batch size than was actually the case, leading to
premature termination of the scan batch which could have
a negative impact on performance of SPJ scans. To correct
this, only the actual read length part of an API request
is now reported in such cases. (Bug #85408, Bug
#25702850)

* Data node binaries for Solaris 11 built using Oracle
Developer Studio 12.5 on SPARC platforms failed with bus
errors. (Bug #85390, Bug #25695818)

* When compiling the NDB kernel with gcc version 6.0.0 or
later, it is now built using -flifetime-dse=1. (Bug
#85381, Bug #25690926)


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