MySQL Cluster 7.2.20 has been released

[Surya Narayana Murthy Narkedimilli]

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 7.2.20, 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 7.2.20 (5.5.43-ndb-7.2.20) (2015-04-13)


   MySQL Cluster NDB 7.2.20 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 5.5.43 (see Changes in MySQL 5.5.43 (Not yet
   released)
   (http://dev.mysql.com/doc/relnotes/mysql/5.5/en/news-5-5-43.h
   tml)).

   Bugs Fixed

     * It was found during testing that problems could arise
       when the node registered as the arbitrator disconnected
       or failed during the arbitration process.
       In this situation, the node requesting arbitration could
       never receive a positive acknowledgement from the
       registered arbitrator; this node also lacked a stable set
       of members and could not initiate selection of a new
       arbitrator.
       Now in such cases, when the arbitrator fails or loses
       contact during arbitration, the requesting node
       immediately fails rather than waiting to time out. (Bug
       #20538179)

     * The maximum failure time calculation used to ensure that
       normal node failure handling mechanisms are given time to
       handle survivable cluster failures (before global
       checkpoint watchdog mechanisms start to kill nodes due to
       GCP delays) was excessively conservative, and neglected
       to consider that there can be at most
       number_of_data_nodes / NoOfReplicas node failures before
       the cluster can no longer survive. Now the value of
       NoOfReplicas is properly taken into account when
       performing this calculation. (Bug #20069617, Bug
       #20069624)
       References: See also Bug #19858151, Bug #20128256, Bug
       #20135976.

     * When a data node fails or is being restarted, the
       remaining nodes in the same nodegroup resend to
       subscribers any data which they determine has not already
       been sent by the failed node. Normally, when a data node
       (actually, the SUMA kernel block) has sent all data
       belonging to an epoch for which it is responsible, it
       sends a SUB_GCP_COMPLETE_REP signal, together with a
       count, to all subscribers, each of which responds with a
       SUB_GCP_COMPLETE_ACK. When SUMA receives this
       acknowledgment from all subscribers, it rports this to
       the other nodes in the same nodegroup so that they know
       that there is no need to resend this data in case of a
       subsequent node failure. If a node failed before all
       subscribers sent this acknowledgement but before all the
       other nodes in the same nodegroup received it from the
       failing node, data for some epochs could be sent (and
       reported as complete) twice, which could lead to an
       unplanned shutdown.
       The fix for this issue adds to the count reported by
       SUB_GCP_COMPLETE_ACK a list of identifiers which the
       receiver can use to keep track of which buckets are
       completed and to ignoreany duplicate reported for an
       already completed bucket. (Bug #17579998)

     * When performing a restart, it was sometimes possible to
       find a log end marker which had been written by a
       previous restart, and that should have been invalidated.
       Now when when searching for the last page to invalidate,
       the same search algorithm is used as when searching for
       the last page of the log to read. (Bug #76207, Bug
       #20665205)

     * When reading and copying transporter short signal data,
       it was possible for the data to be copied back to the
       same signal with overlapping memory. (Bug #75930, Bug
       #20553247)

     * When a bulk delete operation was committed early to avoid
       an additional round trip, while also returning the number
       of affected rows, but failed with a timeout error, an SQL
       node performed no verification that the transaction was
       in the Committed state. (Bug #74494, Bug #20092754)
       References: See also Bug #19873609.

     * Cluster API: When a transaction is started from a cluster
       connection, Table and Index schema objects may be passed
       to this transaction for use. If these schema objects have
       been acquired from a different connection
       (Ndb_cluster_connection object), they can be deleted at
       any point by the deletion or disconnection of the owning
       connection. This can leave a connection with invalid
       schema objects, which causes an NDB API application to
       fail when these are dereferenced.
       To avoid this problem, if your application uses multiple
       connections, you can now set a check to detect sharing of
       schema objects between connections when passing a schema
       object to a transaction, using the
       NdbTransaction::setSchemaObjectOwnerChecks() method added
       in this release. When this check is enabled, the schema
       objects having the same names are acquired from the
       connection and compared to the schema objects passed to
       the transaction. Failure to match causes the application
       to fail with an error. (Bug #19785977)

     * Cluster API: The increase in the default number of
       hashmap buckets (DefaultHashMapSize API node
       configuration parameter) from 240 to 3480 in MySQL
       Cluster NDB 7.2.11 increased the size of the internal
       DictHashMapInfo::HashMap type considerably. This type was
       allocated on the stack in some getTable() calls which
       could lead to stack overflow issues for NDB API users.
       To avoid this problem, the hashmap is now dynamically
       allocated from the heap. (Bug #19306793)

     * Cluster API: A scan operation, whether it is a single
       table scan or a query scan used by a pushed join, stores
       the result set in a buffer. This maximum size of this
       buffer is calculated and preallocated before the scan
       operation is started. This buffer may consume a
       considerable amount of memory; in some cases we observed
       a 2 GB buffer footprint in tests that executed 100
       parallel scans with 2 single-threaded (ndbd) data nodes.
       This memory consumption was found to scale linearly with
       additional fragments.
       A number of root causes, listed here, were discovered
       that led to this problem:

          + Result rows were unpacked to full NdbRecord format
            before they were stored in the buffer. If only some
            but not all columns of a table were selected, the
            buffer contained empty space (essentially wasted).

          + Due to the buffer format being unpacked, VARCHAR and
            VARBINARY columns always had to be allocated for the
            maximum size defined for such columns.

          + BatchByteSize and MaxScanBatchSize values were not
            taken into consideration as a limiting factor when
            calculating the maximum buffer size.
       These issues became more evident in NDB 7.2 and later
       MySQL Cluster release series. This was due to the fact
       buffer size is scaled by BatchSize, and that the default
       value for this parameter was increased fourfold (from 64
       to 256) beginning with MySQL Cluster NDB 7.2.1.
       This fix causes result rows to be buffered using the
       packed format instead of the unpacked format; a buffered
       scan result row is now not unpacked until it becomes the
       current row. In addition, BatchByteSize and
       MaxScanBatchSize are now used as limiting factors when
       calculating the required buffer size.
       Also as part of this fix, refactoring has been done to
       separate handling of buffered (packed) from handling of
       unbuffered result sets, and to remove code that had been
       unused since NDB 7.0 or earlier. The NdbRecord class
       declaration has also been cleaned up by removing a number
       of unused or redundant member variables. (Bug #73781, Bug
       #75599, Bug #19631350, Bug #20408733)


On behalf of the Oracle/MySQL Build and Release Team,
Murthy Narkedimilli