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MySQL Cluster 7.3.6 has been released
Posted by: Sowmya Dass
Date: July 12, 2014 11:03AM

Dear MySQL users,

MySQL Cluster is the distributed, shared-nothing variant of MySQL. This
storage engine provides:

     - Real-time performance based on in-memory storage (with
       checkpointing to disk)
     - Read & write scalability through transparent auto-sharding
     - 99.999% High Availability with no single point of failure and
       on-line maintenance
     - SQL and NoSQL API (including C++, Java, http, Memcached and
     - Active-Active/Multi-Master geographic replication

MySQL Cluster 7.3.6, 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 Cluster NDB 7.3.6 (5.6.19-ndb-7.3.6) (2014-07-11)

   MySQL Cluster NDB 7.3.6 is a new release of MySQL Cluster, based
   on MySQL Server 5.6 and including features from version 7.3 of the
   NDB storage engine, as well as fixing a number of recently
   discovered bugs in previous MySQL Cluster releases.

   Obtaining MySQL Cluster NDB 7.3.  MySQL Cluster NDB 7.3 source
   code and binaries can be obtained from

   For an overview of changes made in MySQL Cluster NDB 7.3, see
   MySQL Cluster Development in MySQL Cluster NDB 7.3

   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 5.6.19 (see Changes in MySQL 5.6.19 (2014-05-30)

   Functionality Added or Changed

     * Cluster API: Added as an aid to debugging the ability to
       specify a human-readable name for a given Ndb object and later
       to retrieve it. These operations are implemented,
       respectively, as the setNdbObjectName() and getNdbObjectName()
       To make tracing of event handling between a user application
       and NDB easier, you can use the reference (from getReference()
       followed by the name (if provided) in printouts; the reference
       ties together the application Ndb object, the event buffer,
       and the NDB storage engine's SUMA block. (Bug #18419907)

   Bugs Fixed

     * Cluster API: When two tables had different foreign keys with
       the same name, ndb_restore considered this a name conflict and
       failed to restore the schema. As a result of this fix, a slash
       character (/) is now expressly disallowed in foreign key
       names, and the naming format parent_id/child_id/fk_name is now
       enforced by the NDB API. (Bug #18824753)

     * Processing a NODE_FAILREP signal that contained an invalid
       node ID could cause a data node to fail. (Bug #18993037, Bug
       References: This bug is a regression of Bug #16007980.

     * When building out of source, some files were written to the
       source directory instead of the build dir. These included the files used for creating ClusterJ jars and the
       pom.xml file used by In addition,
       ndbinfo.sql was written to the build directory, but marked as
       output to the source directory in CMakeLists.txt. (Bug
       #18889568, Bug #72843)

     * Adding a foreign key failed with NDB Error 208 if the parent
       index was parent table's primary key, the primary key was not
       on the table's initial attributes, and the child table was not
       empty. (Bug #18825966)

     * When an NDB table served as both the parent table and a child
       table for 2 different foreign keys having the same name,
       dropping the foreign key on the child table could cause the
       foreign key on the parent table to be dropped instead, leading
       to a situation in which it was impossible to drop the
       remaining foreign key. This situation can be modelled using
       the following CREATE TABLE statements:
	CREATE TABLE parent (
    	id INT NOT NULL,
    	PRIMARY KEY (id)

    	id INT NOT NULL,
    	parent_id INT,
    	PRIMARY KEY (id),
    	INDEX par_ind (parent_id),

    	FOREIGN KEY (parent_id)
    	REFERENCES parent(id)

	CREATE TABLE grandchild (
    	id INT,
    	parent_id INT,
    	INDEX par_ind (parent_id),

	FOREIGN KEY (parent_id)
    	REFERENCES child(id)
       With the tables created as just shown, the issue occured when
       executing the statement ALTER TABLE child DROP FOREIGN KEY
       parent_id, because it was possible in some cases for NDB to
       drop the foreign key from the grandchild table instead. When
       this happened, any subsequent attempt to drop the foreign key
       from either the child or from the grandchild table failed.
       (Bug #18662582)

     * ndbmtd supports multiple parallel receiver threads, each of
       which performs signal reception for a subset of the remote
       node connections (transporters) with the mapping of
       remote_nodes to receiver threads decided at node startup.
       Connection control is managed by the multi-instance TRPMAN
       block, which is organized as a proxy and workers, and each
       receiver thread has a TRPMAN worker running locally.
       The QMGR block sends signals to TRPMAN to enable and disable
       communications with remote nodes. These signals are sent to
       the TRPMAN proxy, which forwards them to the workers. The
       workers themselves decide whether to act on signals, based on
       the set of remote nodes they manage.
       The current isuue arises because the mechanism used by the
       TRPMAN workers for determining which connections they are
       responsible for was implemented in such a way that each worker
       thought it was responsible for all connections. This resulted
       in the TRPMAN actions for OPEN_COMORD, ENABLE_COMREQ, and
       CLOSE_COMREQ being processed multiple times.
       The fix keeps TRPMAN instances (receiver threads) executing
       addition, the correct TRPMAN instance is now chosen when
       routing from this instance for a specific remote connection.
       (Bug #18518037)

       increasing the number of data nodes in the cluster from 4 to
       16 led to a crash of the data nodes. This issue was shown to
       be a regression caused by previous fix which added a new dump
       handler using a dump code that was already in use (7019),
       which caused the command to execute two different handlers
       with different semantics. The new handler was assigned a new
       DUMP code (7024). (Bug #18550318)
       References: This bug is a regression of Bug #14220269.

     * When running with a very slow main thread, and one or more
       transaction coordinator threads, on different CPUs, it was
       possible to encounter a timeout when sending a
       DIH_SCAN_GET_NODESREQ signal, which could lead to a crash of
       the data node. Now in such cases the timeout is avoided. (Bug

     * During data node failure handling, the transaction coordinator
       performing takeover gathers all known state information for
       any failed TC instance transactions, determines whether each
       transaction has been committed or aborted, and informs any
       involved API nodes so that they can report this accurately to
       their clients. The TC instance provides this information by
       sending TCKEY_FAILREF or TCKEY_FAILCONF signals to the API
       nodes as appropriate top each affected transaction.
       In the event that this TC instance does not have a direct
       connection to the API node, it attempts to deliver the signal
       by routing it through another data node in the same node group
       as the failing TC, and sends a GSN_TCKEY_FAILREFCONF_R signal
       to TC block instance 0 in that data node. A problem arose in
       the case of multiple transaction cooridnators, when this TC
       instance did not have a signal handler for such signals, which
       led it to fail.
       This issue has been corrected by adding a handler to the TC
       proxy block which in such cases forwards the signal to one of
       the local TC worker instances, which in turn attempts to
       forward the signal on to the API node. (Bug #18455971)

     * A local checkpoint (LCP) is tracked using a global LCP state
       (c_lcpState), and each NDB table has a status indicator which
       indicates the LCP status of that table (tabLcpStatus). If the
       global LCP state is LCP_STATUS_IDLE, then all the tables
       should have an LCP status of TLS_COMPLETED.
       When an LCP starts, the global LCP status is LCP_INIT_TABLES
       and the thread starts setting all the NDB tables to
       TLS_ACTIVE. If any tables are not ready for LCP, the LCP
       initialization procedure continues with CONTINUEB signals
       until all tables have become available and been marked
       TLS_ACTIVE. When this initialization is complete, the global
       LCP status is set to LCP_STATUS_ACTIVE.
       This bug occurred when the following conditions were met:

          + An LCP was in the LCP_INIT_TABLES state, and some but not
            all tables had been set to TLS_ACTIVE.

          + The master node failed before the global LCP state
            changed to LCP_STATUS_ACTIVE; that is, before the LCP
            could finish processing all tables.

          + The NODE_FAILREP signal resulting from the node failure
            was processed before the final CONTINUEB signal from the
            LCP initialization process, so that the node failure was
            processed while the LCP remained in the LCP_INIT_TABLES
       Following master node failure and selection of a new one, the
       new master queries the remaining nodes with a MASTER_LCPREQ
       signal to determine the state of the LCP. At this point, since
       the LCP status was LCP_INIT_TABLES, the LCP status was reset
       to LCP_STATUS_IDLE. However, the LCP status of the tables was
       not modified, so there remained tables with TLS_ACTIVE.
       Afterwards, the failed node is removed from the LCP. If the
       LCP status of a given table is TLS_ACTIVE, there is a check
       that the global LCP status is not LCP_STATUS_IDLE; this check
       failed and caused the data node to fail.
       Now the MASTER_LCPREQ handler ensures that the tabLcpStatus
       for all tables is updated to TLS_COMPLETED when the global LCP
       status is changed to LCP_STATUS_IDLE. (Bug #18044717)

     * When performing a copying ALTER TABLE operation, mysqld
       creates a new copy of the table to be altered. This
       intermediate table, which is given a name bearing the prefix
       #sql-, has an updated schema but contains no data. mysqld then
       copies the data from the original table to this intermediate
       table, drops the original table, and finally renames the
       intermediate table with the name of the original table.
       mysqld regards such a table as a temporary table and does not
       include it in the output from SHOW TABLES; mysqldump also
       ignores an intermediate table. However, NDB sees no difference
       between such an intermediate table and any other table. This
       difference in how intermediate tables are viewed by mysqld
       (and MySQL client programs) and by the NDB storage engine can
       give rise to problems when performing a backup and restore if
       an intermediate table existed in NDB, possibly left over from
       a failed ALTER TABLE that used copying. If a schema backup is
       performed using mysqldump and the mysql client, this table is
       not included. However, in the case where a data backup was
       done using the ndb_mgm client's BACKUP command, the
       intermediate table was included, and was also included by
       ndb_restore, which then failed due to attempting to load data
       into a table which was not defined in the backed up schema.
       To prevent such failures from occurring, ndb_restore now by
       default ignores intermediate tables created during ALTER TABLE
       operations (that is, tables whose names begin with the prefix
       #sql-). A new option --exclude-intermediate-sql-tables is
       added that makes it possible to override the new behavior. The
       option's default value is TRUE; to cause ndb_restore to revert
       to the old behavior and to attempt to restore intermediate
       tables, set this option to FALSE. (Bug #17882305)

     * The logging of insert failures has been improved. This is
       intended to help diagnose occasional issues seen when writing
       to the mysql.ndb_binlog_index table. (Bug #17461625)

     * The DEFINER column in the INFORMATION_SCHEMA.VIEWS table
       contained erroneous values for views contained in the ndbinfo
       information database. This could be seen in the result of a
       query such as SELECT TABLE_NAME, DEFINER FROM

     * Employing a CHAR column that used the UTF8 character set as a
       table's primary key column led to node failure when restarting
       data nodes. Attempting to restore a table with such a primary
       key also caused ndb_restore to fail. (Bug #16895311, Bug

     * Disk Data: Setting the undo buffer size used by
       InitialLogFileGroup to a value greater than that set by
       SharedGlobalMemory prevented data nodes from starting; the
       data nodes failed with Error 1504 Out of logbuffer memory.
       While the failure itself is expected behavior, the error
       message did not provide sufficient information to diagnose the
       actual source of the problem; now in such cases, a more
       specific error message Out of logbuffer memory (specify
       smaller undo_buffer_size or increase SharedGlobalMemory) is
       supplied. (Bug #11762867, Bug #55515)

     * Cluster Replication: When using NDB$EPOCH_TRANS, conflicts
       between DELETE operations were handled like conflicts between
       updates, with the primary rejecting the transaction and
       dependents, and realigning the secondary. This meant that
       their behavior with regard to subsequent operations on any
       affected row or rows depended on whether they were in the same
       epoch or a different one: within the same epoch, they were
       considered conflicting events; in different epochs, they were
       not considered in conflict.
       This fix brings the handling of conflicts between deletes by
       NDB$EPOCH_TRANS with that performed when using NDB$EPOCH for
       conflict detection and resolution, and extends testing with
       NDB$EPOCH and NDB$EPOCH_TRANS to include "delete-delete"
       conflicts, and encapsulate the expected result, with
       transactional conflict handling modified so that a conflict
       between DELETE operations alone is not sufficient to cause a
       transaction to be considered in conflict. (Bug #18459944)

     * Cluster API: When an NDB data node indicates a buffer overflow
       via an empty epoch, the event buffer places an inconsistent
       data event in the event queue. When this was consumed, it was
       not removed from the event queue as expected, causing
       subsequent nextEvent() calls to return 0. This caused event
       consumption to stall because the inconsistency remained
       flagged forever, while event data accumulated in the queue.
       Event data belonging to an empty inconsistent epoch can be
       found either at the beginning or somewhere in the middle.
       pollEvents() returns 0 for the first case. This fix handles
       the second case: calling nextEvent() call dequeues the
       inconsistent event before it returns. In order to benefit from
       this fix, user applications must call nextEvent() even when
       pollEvents() returns 0. (Bug #18716991)

     * Cluster API: The pollEvents() method returned 1, even when
       called with a wait time equal to 0, and there were no events
       waiting in the queue. Now in such cases it returns 0 as
       expected. (Bug #18703871)

On Behalf of the MySQL Cluster and the Oracle/MySQL RE Team
Sowmya Dass

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Written By
MySQL Cluster 7.3.6 has been released
July 12, 2014 11:03AM

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