MySQL Tech-Feed (en)

If and how to use Galera Cluster for MySQL has been described already by many others…

In this article we focus on the question: When is Galera Cluster NOT the right solution for you?

These thoughts also apply to Percona XtraDB Cluster (PXC) and MariaDB Galera Cluster.

• Galera Cluster currently supports only InnoDB (and TokuDB?) tables properly. You should avoid to use MyISAM or MEMORY tables. Otherwise data consistency is not guaranteed.
• It is wise to use Galera Cluster only if your software vendor …

Database migration tools

A generic database migration tool to MySQL and MariaDB is the MySQL Workbench.

An alternative is the old MySQL Migration Tool Kit.

Recommended by MariaDB Foundation: Sqlines.

Adabas D to MariaDB migration

Project migrating an Adabas D database to MariaDB is in progress. More information are expected before end of 2015.

Oracle to MySQL or MariaDB migration

Data Migration Tools

• MyOraDump is a tool to export data from an Oracle database to MySQL or MariaDB. …

The InnoDB Flush Method has changed. This can have an impact on InnoDB write Performance.

The following example should work for you:

CREATE TABLE spec(txt VARCHAR(255));

INSERT INTO spec values (‘bla\tbla\nbla’); INSERT INTO spec values (’\n\tb)’); INSERT INTO spec values (‘abc\n\tb)xyz’);

SELECT * FROM spec;

SELECT * FROM spec WHERE txt LIKE ‘\n\tb)’; SELECT * FROM spec WHERE txt LIKE ‘%\n\tb)%’; SELECT * FROM spec WHERE txt REGEXP ‘^\n\tb)$’; SELECT * FROM spec WHERE txt REGEXP ‘\n\tb)’;

A MySQL customer of FromDual has different manufacturing plants spread across the globe. They are operated by local companies. FromDuals customer wants to maintain the manufacturing receipts centralized in a MySQL database in the Head Quarter in Europe. Each manufacturing plant should only see their specific data.

Manufacturing log information should be reported backup to European Head Quarter MySQL database.

The process was designed as follows:

Preparation of Proof of Concept (PoC)

To simulate all cases …

We finally got the results. The table does NOT have a Primary Key and/or an index on lSessionId:

CREATE TABLE IF NOT EXISTS `genLogins` (
  `lSessionId` varchar(128) NOT NULL,
  `lUid` int(8) NOT NULL DEFAULT '0',
  `lLang` char(2) NOT NULL,
  `lTimeout` int(10) NOT NULL DEFAULT '0',
  `lReloadsess` enum('y','n') NOT NULL DEFAULT 'n',
  `lTsexpire` int(10) NOT NULL DEFAULT '0'
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

Please also read: Disadvantages of explicitly NOT using …

We typically suggest our customers to use our MySQL/Galera Cluster my.cnf configuration template to avoid MySQL configuration and performance problems.

And we are paranoid as well. Thus we enable all useful logging:

wsrep_log_conflicts = 1

But this has also some consequences of more visibility…

If you monitor carefully your Galera Cluster for example with the FromDual Performance Monitor for MySQL and MariaDB, you might probably see some strange values increasing from time to time:

mysql< SHOW …

From time to time we see at Galera Cluster customer engagements the following, for me scary, warning in the MySQL error log:

[Warning] WSREP: last inactive check more than PT1.5S ago (PT7.06159S), skipping check

We mostly see this in VMware set-ups. Some further enquiry with the Galera developers did not give a satisfying answer:

This can be seen on bare metal as well - with poorly configured mysqld, O/S, or simply being overloaded. All it means is that this thread could not get CPU time for 7.1 seconds. …

Before I forget it and have to search again here a short note about how to rename a MySQL Partition:

My dream:

ALTER TABLE history RENAME PARTITION p2015_kw10 INTO p2015_kw09;

In reality:

ALTER TABLE history
REORGANIZE PARTITION p2015_kw10 INTO (
PARTITION p2015_kw09 VALUES LESS THAN (UNIX_TIMESTAMP('2015-03-02 00:00:00'))
);

Caution: REORGANIZE PARTITION causes a full copy of the whole partition!

Hint: I assume it would be very easy for MySQL or MariaDB to make this DDL command an in-place …

This error is NOT serious. It happens, when one MPM run overpasses an older one or when you start a second run manually.

We will fix this issue in one of our next releases when we completely have redesigned the MPM agent…

MySQL Enterprise Backup (MEB) has the capability to make real incremental (differential and cumulative?) backups. The actual releases are quite cool and you should really look at it…

Unfortunately the original MySQL documentation is much too complicated for my simple mind. So I did some testing and simplified it a bit for our customers…

If you want to dive into the original documentation please look here: Making an Incremental Backup .

If you want to use MySQL Enterprise Backup please let us …

Hi burps

In Zabbix we have “hosts”. In MPM a host is either a server (DBSERVER01) or a MySQL Instance (mysqld).

The host section [DBSERVER01] or [mysqld] overwrites the [default] section.

The MPM Agent is triggered by the mpm Module in the Server section. So it needs only ONE mpm module per MPM Agent.

In your case it most probably makes sense to have 2 sections: One for the Server and one for the Database:

[DBSERVER01] Modules = mpm server

[mysqld] Modules = process mysql myisam innodb …

MySQL Enterprise Monitor (MEM) has by default no Event Handlers created and activated. These Event Handlers you have to define yourself according to your needs.

In this article we discuss how to create MySQL Enterprise Monitor Event Handlers with MEM v.3.0.18. For other (older) versions the steps may vary…

Task: Event Handler for maximum Connections reached

We would like to be notified by MySQL Enterprise Monitor when the number of connections is near to max_connections.

For this we search first …

FromDual has the pleasure to announce the release of the new version 1.0.0 of its widely used Nagios and Icinga plugins for MySQL, Galera Cluster, MariaDB and Percona Server.

All plugins are basically renewed and should now work all correctly.

The new Nagios/Icinga plugins can be downloaded here.

In the inconceivable case that you find a bug in the Nagios/Icinga plugins please report it to our bug tracker.

Any feedback, statements and testimonials are welcome as well! Please send them to …

MySQL provides some great enterprise features beside the MySQL Server. The ones we are asked the most at customers are:

• MySQL Enterprise Backup (MEB)
• MySQL Enterprise Monitor (MEM) and
• MySQL Enterprise Workbench (MWB)

MySQL Enterprise Backup (MEB)

MySQL Enterprise Backup (MEB) is an alternative to the mysqldump backup utility. Its big advantage is its fast backup but even faster restore performance. This is a must for all MySQL users having bigger databases than let’s say 10 to 20 Gigabytes and/or …

Sometimes we face the situation where we have a full MySQL database backup done with mysqldump and then we have to restore and recover just one single table out of our huge mysqldump file.
Further our mysqldump backup was taken hours ago so we want to recover all the changes on that table since our backup was taken up to the end.

In this blog article we cover all the steps needed to achieve this goal for MySQL and MariaDB.

Recommendation: It is recommended to do theses steps on a testing system and then …

We recently run into some troubles with max_allowed_packet size problems during backups with the FromDual Backup/Recovery Manager and thus I investigated a bit more in the symptoms of such problems.

Read more about: max_allowed_packet.

A general rule for max_allowed_packet size to avoid problems is: All clients and the server should have set the same value for max_allowed_packet size!

I prepared some data for the test which looked as follows:

mysql> SELECT id, LEFT(data, 30), LENGTH(data), ts FROM test; …

Hello oli,

every user/process on a UNIX system has some user limits. There are some soft (S) and hard (H) user limits. Soft limits a user can change himself up to the hard limits.

You can find you own user limits as follows:

shell> ulimit -aS | grep 'open'
open files                      (-n) 1024

shell> ulimit -aH | grep 'open'
open files                      (-n) 4096

and the user limits of an already running process as follows:

shell> cat /proc/`pidof mysqld`/limits | egrep 'Limit|open …

Hello oli,

it looks like you have enabled skip_name_resolve in your my.cnf.
This prevents MySQL to do (DNS) host lookups. If you have created some users with explicit host names MySQL wants to tell you now that you cannot use these users any more with this configuration. Example:

mysql> GRANT ALL ON *.* TO 'root'@'master';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> SHOW WARNINGS; …

Looking at Percona Server source code we can find the following:

storage/innobase/srv/srv0srv.cc

export_vars.innodb_checkpoint_age     = (log_sys->lsn - log_sys->last_checkpoint_lsn);
export_vars.innodb_checkpoint_max_age = log_sys->max_checkpoint_age;

Looking at the code we can see how output of SHOW ENGINE INNODB STATUS\G is produced:

storage/innobase/log/log0log.cc

void log_print(FILE* file)
{

 fprintf(file,
         "Log sequence number " LSN_PF "\n"
         "Log flushed up to   " …