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MySQL 5.5.38 Overview and Highlights

Chris on MySQL - June 13, 2014 - 2:28am GMT

MySQL 5.5.38 was recently released (it is the latest MySQL 5.5, is GA), and is available for download here:

http://downloads.skysql.com/archive/index/p/mysql/v/5.5.38

This release, similar to the last 5.5 release, is mostly uneventful.

Out of the mere 13 bugs, most were benign, but I thought there were two worth mentioning (just because one is a slight performance improvement for InnoDB, and the other relates to slave consistency, so always important to see if it could affect you):

  1. InnoDB: For each insert, memset would be called three times to allocate memory for system fields. To reduce CPU usage, the three memset calls are now combined into a single call. (Bug #17858679, Bug #71014)
  2. Replication: When used on a table employing a transactional storage engine, a failed TRUNCATE TABLE was still written to the binary log and thus replayed on the slave. This could lead to inconsistency when the master retained data that was removed on the slave. Now in such cases TRUNCATE TABLE is logged only when it executes successfully. (Bug #17942050, Bug #71070)

For reference, the full 5.5.38 changelog can be viewed here:

http://dev.mysql.com/doc/relnotes/mysql/5.5/en/news-5-5-38.html

Hope this helps.

 

MariaDB 5.5.38 Overview and Highlights

Chris on MySQL - June 12, 2014 - 5:11am GMT

MariaDB 5.5.38 was recently released (it is the latest MariaDB 5.5), and is available for download here:

https://downloads.mariadb.org/mariadb/5.5.38/

This is a maintenance release, and so there are not too many big changes of note, just a number of normal bug fixes. However, there are a few items worth mentioning:

  • Includes all bugfixes and updates from MySQL 5.5.38
  • XtraDB updated to the version from Percona Server 5.5.37-35.0
  • TokuDB updated to version 7.1.6
  • MariaDB on Power: With this release of MariaDB we’re introducing binary tarball builds created on a Power7 box running Red Hat 6. They’re listed on the downloads page in the “OS/CPU” column as “Linux ppc64″. We welcome your feedback on these new packages!

If interested, there is more about the 5.5.38 release here:

https://mariadb.com/kb/en/mariadb-5538-release-notes/

And the full list of fixed bugs and changes in MariaDB 5.5.38 can be found here:

https://mariadb.com/kb/en/mariadb-5538-changelog/

Hope this helps.

 

MySQL 5.6.19 Overview and Highlights

Chris on MySQL - June 11, 2014 - 5:26pm GMT

MySQL 5.6.19 was recently released (it is the latest MySQL 5.6, is GA), and is available for download here.

I should actually call this post “5.6.18 and 5.6.19 Overview and Highlights”.

The 5.6 “Release Notes” Index provides an entry/changelog for 5.6.18 and says it was released 2014-04-11. However, it’s not available in the community download archives. This isn’t mentioned in the 5.6.18 changelogs, but it is in the 5.6.19 changelogs, where it says:

“There is no MySQL Community Server 5.6.18. That version number was used for an out-of-schedule release of the Enterprise Edition to address the OpenSSL ‘Heartbleed’ issue. This issue did not affect the Community Edition because it uses yaSSL, not OpenSSL, so a new release of the Community Server was not needed, and 5.6.17 is followed by 5.6.19.”

While Heartbleed did not affect the *community* versions of MySQL 5.6, it does affect the *commercial* versions of MySQL 5.6 (less than 5.6.18). This is because the *community* version of MySQL 5.6 was built using yaSSL (unaffected SSL library), whereas the *commercial* version of MySQL 5.6 was build using OpenSSL (vulnerable SSL library). So take note of this if you’re running *commercial* MySQL 5.6.

There is also an important “known limitation” of this release, which affects MySQL 5.6.10 through and including 5.6.18, which is:

“If you have InnoDB tables with full-text search indexes and you are upgrading from MySQL 5.6.10 to a MySQL version up to and including MySQL 5.6.18, the server will fail to start after the upgrade (Bug#72079). This bug is fixed in MySQL 5.6.19. As a workaround, remove full-text search indexes prior to upgrading and rebuild full-text search indexes after the upgrade is completed.”

So beware of this if you’re running 5.6.10+, using InnoDB full-text search indexes, and plan on upgrading to 5.6.11 – 5.6.18.

There was also one other bug fixed in the 5.6.18 release notes, but just a rather obscure one related to running a collated subquery on an ARCHIVE table containing an AUTO_INCREMENT column.

Now, as for 5.6.19, there are more fixes:

2 Functionality Added or Changed, which all seem quite minor:

  1. The obsolete and unmaintained charset2html utility has been removed from MySQL distributions. (Bug #71897, Bug #18352347)
  2. The mysqlbug, mysql_waitpid, and mysql_zap utilities have been deprecated and will be removed in MySQL 5.7.

And I counted 32 bug fixes (6 InnoDB, 7 Replication, and 19 misc. bugs).

I found the more important/noteworthy bug fixes to be:

  • InnoDB: After upgrading from 5.6.10 to MySQL versions up to and including MySQL 5.6.18, InnoDB would attempt to rename obsolete full-text search auxiliary tables on server startup, resulting in an assertion failure. (Bug #18634201, Bug #72079)
  • InnoDB: The fix for Bug#17699331 caused a high rate of read/write lock creation and destruction which resulted in a performance regression. (Bug #18345645, Bug #71708). This regression bug affects versions 5.6.16 – 5.6.18.
  • InnoDB: For each insert, memset would be called three times to allocate memory for system fields. To reduce CPU usage, the three memset calls are now combined into a single call. (Bug #17858679, Bug #71014)
  • InnoDB: Enabling the InnoDB Table Monitor would result in a ib_table->stat_initialized assertion failure. (Bug #17039528, Bug #69641)
  • InnoDB: With innodb_max_dirty_pages_pct=0 buffer pool flushing would not be initiated until the percentage of dirty pages reached at least 1%, which would leave up to 1% of dirty pages unflushed. (Bug #13029450, Bug #62534)
  • Replication: Log rotation events could cause group_relay_log_pos to be moved forward incorrectly within a group. This meant that, when the transaction was retried, or if the SQL thread was stopped in the middle of a transaction following one or more log rotations (such that the transaction or group spanned multiple relay log files), part or all of the group was silently skipped. This issue has been addressed by correcting a problem in the logic used to avoid touching the coordinates of the SQL thread when updating the log position as part of a relay log rotation whereby it was possible to update the SQL thread’s coordinates when not using a multi-threaded slave, even in the middle of a group. (Bug #18482854)
  • Replication: In certain cases, the server mishandled triggers and stored procedures that tried to modify other tables when called by CREATE TABLE … SELECT. This is now handled correctly as an error. (Bug #18137535)
  • Replication: When used on a table employing a transactional storage engine, a failed TRUNCATE TABLE was still written to the binary log and thus replayed on the slave. This could lead to inconsistency when the master retained data that was removed on the slave. Now in such cases TRUNCATE TABLE is logged only when it executes successfully. (Bug #17942050, Bug #71070)
  • For indexes on prefixes or character string columns, index corruption could occur for assignment of binary data to the column due to improper character counting. (Bug #18359924)
  • mysqldump could create table definitions in the dump file that resulted in Too many columns errors when reloading the dump file. (Bug #17477959)
  • On Windows, REPAIR TABLE and OPTIMIZE TABLE failed for MyISAM tables with .MYD files larger than 4GB. (Bug #69683, Bug #17235179)

Conclusions:

  • If you’re running 5.6 *commercial*, and not running 5.6.18 or 5.6.19, you need to upgrade now.
  • If you’re running 5.6.10 through 5.6.18 and using InnoDB full-text indexes, and if you upgrade to a 5.6 version less than 5.6.19, you will encounter problems (though there is a work-around mentioned above).
  • The InnoDB fixes were somewhat specific, so I would only consider the regression bug that affected 5.6.16 – 5.6.18 to be an overall worrier, but read through them to be sure none of the others affect you.
  • Similarly, the couple replication fixes were also somewhat specific, so read through those to see if they could affect you.

The full changelogs can be viewed here (which has more details about all of the bugs listed above), 5.6.18 and 5.6.19 listed respectively:

http://dev.mysql.com/doc/relnotes/mysql/5.6/en/news-5-6-18.html
http://dev.mysql.com/doc/relnotes/mysql/5.6/en/news-5-6-19.html

Hope this helps.

 

MariaDB is the default implementation of MySQL in Red Hat Enterprise Linux 7

Chris on MySQL - June 11, 2014 - 3:23am GMT

It was announced that MariaDB is now the default implementation of MySQL in the newly released Red Hat Enterprise Linux 7.

News of the Red Hat Enterprise Linux 7 can be found here.

And mention of MariaDB replacing MySQL as the default implementation is referenced in their release notes here.

The full change log entry reads:

MariaDB 5.5

  • MariaDB is the default implementation of MySQL in Red Hat Enterprise Linux 7. MariaDB is a community-developed fork of the MySQL database project, and provides a replacement for MySQL. MariaDB preserves API and ABI compatibility with MySQL and adds several new features; for example, a non-blocking client API library, the Aria and XtraDB storage engines with enhanced performance, better server status variables, and enhanced replication.

    Detailed information about MariaDB can be found at https://mariadb.com/kb/en/what-is-mariadb-55/.

 

What exactly does log_warnings=2 log?

Chris on MySQL - June 6, 2014 - 7:29pm GMT

Have you ever wondered exactly does log_warnings=2 log? Well, I have, and finally decided to check the code. (The manual used to mention setting this to 2 for diagnosing some connection-related problems, but I didn’t run into that comment in my most recent search.)

Basically, in recent 5.6 source code, we find “log_warnings > 1″ in 7 files. In 5.5 source, it is only in 5 files. Here are the 7 files in 5.6:

filesort.cc (line 460)
log_event.cc (lines 4873, 10020, 11209)
rpl_master.cc (line 912)
rpl_rli_pdb.cc (lines 1538, 1596, 1735, 2066)
rpl_slave.cc (lines 3585, 4684, 5405, 5436)
sql_acl.cc (lines 9591, 9613, 11351)
sql_connect.cc (line 791)

Long story short, the main (most common) ones are when a filesort fails (filesort.cc) or a failed login occurs (sql_acl.cc). Then there are some replication-specific instances where it logs extra info, such as master/slave/binlog info, “ignored” errors, and some summary stats for multi-threaded slave worker threads (rpl_master.cc, rpl_rli_pdb.cc, rpl_slave.cc) (All of the extra replication logging was new to 5.6, fwiw.). If it fails to close a connection that it should close, it logs some info (sql_connect.cc). And lastly, another new option in 5.6 is password expiration support. So if that is enabled and expired for the current user (and log_warnings > 1), then a note is logged to the error log as well (sql_acl.cc line 11351).

Long story long, … I debated posting the relevant code snippets, but after seeing how boring that was going to be, I’ve omitted them.

Fwiw, the max log_warnings in 5.6 on 32-bit is 4294967295 and for 64-bit is 18446744073709547520. However, at least for now anyway, it seems there is no difference between setting this to 2 or 18446744073709547520, as the only current references/actions are for “log_warnings > 1″.

In 5.7, there is some new info added to the log_warnings definition, mostly because of the new 5.7 variable log_error_verbosity. Here is what is says about “log_warnings=2 (or higher)”:

“Setting log_warnings=2 (or higher) is equivalent to log_error_verbosity=3 (errors, warnings, notes), and the server sets log_warnings to 2 if a larger value is specified.”

Hope this helps.

 

MaxScale 0.7.0 Overview and Highlights

Chris on MySQL - June 6, 2014 - 6:24pm GMT

MaxScale 0.7.0 was recently released (it is the 4th alpha, with the beta on the near horizon), and is available for download here.

The release contains a number of new enhancements as well as 8 bugs fixes.

Enhancements:

  1. Galera Support: Enhanced support for Galera cluster to allow Galera to be used as a High Available Cluster with no write contention between the nodes. MaxScale will control access to a Galera Cluster such that one node is designated as the master node to which all write operations will be sent. Read operations will be sent to any of the remaining nodes that are part of the cluster. Should the currently elected master node fail MaxScale will automatically promote one of the remaining nodes to become the new master node.
  2. Multiple Slave Connections: The Read/Write Split query router has been enhanced to allow multiple slaves connections to be created. The number of slave connections is configurable via a parameter in the MaxScale configuration file. Adding multiple connections allows for better load balancing between the slaves and in a pre-requisite for providing improved fault tolerance within the Read/Write Splitter. The selection of which slave to use for a particular read operation can be controlled via options in the router configuration.
  3. Debug Interface Enhancements: A number of new list commands have been added to the debug interface to allow more concise tabular output of certain object types within the interface.
    MaxScale> help list
    Available options to the list command:
       filters    List all the filters defined within MaxScale
       listeners  List all the listeners defined within MaxScale
       modules    Show all currently loaded modules
       services   List all the services defined within MaxScale
       servers    List all the servers defined within MaxScale
       sessions   List all the active sessions within MaxScale
    MaxScale>

    Those objects that are defined in the configuration file can now be referenced by the names used in the configuration file rather than by using memory addresses. This means that services, servers, monitors and filters can all now be referenced using meaningful names provided by the user. Internal objects such as DCB’s and sessions, which are not named in the configuration file still require the use of memory addresses. Two modes of operation of the interface are now available, user mode and developer mode. The user mode restricts access to the feature that allow arbitrary structures to be examined and checks all memory address for validity before allowing access.

  4. Maintenance Mode for Servers: MaxScale now provides a maintenance mode for servers, this mode allows servers to be set such that no new connections will be opened to that server. Also, servers in maintenance mode are not monitored by MaxScale. This allows an administrator to set a server into maintenance mode when it is required to be taken out of use. The connections will then diminish over time and since no new connections are created, the administrator can remove the node from use to perform some maintenance activities.

    Nodes are placed into maintenance mode via the debug interface using the set server command.

    MaxScale> set server datanode3 maintenance

    Nodes are taken out of maintenance using the clear server command.

    MaxScale> clear server datanode3 maintenance
  5. Configurable Monitoring Interval: All monitor plugins now provide a configuration parameter that can be set to control how frequently the MaxScale monitoring is performed.
  6. Replication Lag Heartbeat Monitor: The mysqlmon monitor module now implements a replication heartbeat protocol that is used to determine the lag between updates to the master and those updates being applied to the slave. This information is then made available to routing modules and may be used to determine if a particular slave node may be used or which slave node is most up to date.
  7. Filters API: The first phase of the filter API is available as part of this release. This provides filtering for the statements from the client application to the router. Filtering for the returned results has not yet been implemented and will be available in a future version.

    Three example filters are including in the release

    1. Statement counting Filter – a simple filter that counts the number of SQL statements executed within a session. Results may be viewed via the debug interface.
    2. Query Logging Filter – a simple query logging filter that write all statements for a session into a log file for that session.
    3. Query Rewrite Filter – an example of how filters can alter the query contents. This filter allows a regular expression to be defined, along with replacement text that should be substituted for every match of that regular expression.
  8. MariaDB 10 Replication Support: The mysqlmon monitor module has been updated to support the new syntax for show all slaves status in MariaDB in order to correctly determine the master and slave state of each server being monitor. Determination of MariaDB 10 is automatically performed by the monitor and no configuration is required.
  9. API Versioning: The module interface has been enhanced to allow the API version in use to be reported, along with the status of the module and a short description of the module. The status allows for differentiation of the release status of a plugin to be identified independently of the core of MaxScale. plugins may be designated as “in development”, “alpha”, “beta” or “GA”.
    MaxScale> list modules
    Module Name     | Module Type | Version | API   | Status
    ----------------------------------------------------------------
    regexfilter     | Filter      | V1.0.0  | 1.0.0 | Alpha
    MySQLBackend    | Protocol    | V2.0.0  | 1.0.0 | Alpha
    telnetd         | Protocol    | V1.0.1  | 1.0.0 | Alpha
    MySQLClient     | Protocol    | V1.0.0  | 1.0.0 | Alpha
    mysqlmon        | Monitor     | V1.2.0  | 1.0.0 | Alpha
    readwritesplit  | Router      | V1.0.2  | 1.0.0 | Alpha
    readconnroute   | Router      | V1.0.2  | 1.0.0 | Alpha
    debugcli        | Router      | V1.1.1  | 1.0.0 | Alpha
    MaxScale>
  10. Linking: Following reported issues with incompatibilities between MaxScale and the shared library used by MySQL this version of MaxScale will be statically linked with the MariaDB 5.5 embedded library that it requires. This library is used for internal purposes only and does not result in MaxScale support for other versions of MySQL or MariaDB being affected.

Bug Fixes:

  1. mysql/galera monitors hang when backend fails (443)
  2. Read/Write Splitter closes connection without sending COM_QUIT (424)
  3. Internal thread deadlock (438)
  4. Sessions in invalid state (436)
  5. Router options for Read/Write Split module (359)
  6. Some automated tests have invalid SQL syntax (435)
  7. rwsplit.sh test script has incorrect bash syntax (431)
  8. MaxScale crashes after prolonged use (425)

If you’re not too familiar with MaxScale, you can view a short, 4 minute, overview (as well as read some details) here.

Hope this helps.

 

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