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Max_used_connections per user/account

Shinguz - Thu, 2015-07-30 23:34
Taxonomy upgrade extras: max_used_connectionsuseraccountconnectionconfiguration

How many connections can be opened concurrently against my MySQL or MariaDB database can be configured and checked with the following command:

SHOW GLOBAL VARIABLES LIKE 'max_connections'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 505 | +-----------------+-------+

If this limit was ever reached in the past can be checked with:

SHOW GLOBAL STATUS LIKE 'max_use%'; +----------------------+-------+ | Variable_name | Value | +----------------------+-------+ | Max_used_connections | 23 | +----------------------+-------+

But on MySQL instances with many different applications (= databases/schemas) and thus many different users it is a bit more complicated to find out which of these users have connected how many times concurrently. We can configure how many connections one specific user can have at maximum at the same time with:

SHOW GLOBAL VARIABLES LIKE 'max_user_connections'; +----------------------+-------+ | Variable_name | Value | +----------------------+-------+ | max_user_connections | 500 | +----------------------+-------+

Further we can limit one specific user with:

GRANT USAGE ON *.* TO 'repl'@'%' WITH MAX_CONNECTIONS_PER_HOUR 100 MAX_USER_CONNECTIONS 10;

and check with:

SELECT User, Host, max_connections, max_user_connections FROM mysql.user; +------+---------------+-----------------+----------------------+ | User | Host | max_connections | max_user_connections | +------+---------------+-----------------+----------------------+ | root | localhost | 0 | 0 | | repl | % | 100 | 10 | | repl | 192.168.1.139 | 0 | 0 | +------+---------------+-----------------+----------------------+

But we have currently no chance to check if this limit was reached or nearly reached in the past...

A feature request for this was opened at MySQL wit bug #77888

Solution

If you cannot wait for the implementation here we have a little workaround:

DROP TABLE IF EXISTS mysql.`max_used_connections`; CREATE TABLE mysql.`max_used_connections` ( `USER` char(16) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL, `HOST` char(60) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL, `MAX_USED_CONNECTIONS` bigint(20) NOT NULL, PRIMARY KEY (`USER`, `HOST`) USING HASH ) ENGINE=MEMORY DEFAULT CHARSET=utf8 ; DROP EVENT IF EXISTS mysql.gather_max_used_connections; -- event_scheduler = on CREATE DEFINER=root@localhost EVENT mysql.gather_max_used_connections ON SCHEDULE EVERY 10 SECOND DO INSERT INTO mysql.max_used_connections SELECT user, host, current_connections FROM performance_schema.accounts WHERE user IS NOT NULL AND host IS NOT NULL ON DUPLICATE KEY UPDATE max_used_connections = IF(current_connections > max_used_connections, current_connections, max_used_connections) ; SELECT * FROM mysql.max_used_connections; +--------+-----------+----------------------+ | USER | HOST | MAX_USED_CONNECTIONS | +--------+-----------+----------------------+ | root | localhost | 4 | | zabbix | localhost | 21 | +--------+-----------+----------------------+

Caution: Because we used a MEMORY table those values are reset at every MySQL restart (as it happens with the PERFORMANCE_SCHEMA or the INFORMATION_SCHEMA).

FromDual Backup Manager for MySQL 1.2.2 has been released

Shinguz - Tue, 2015-06-23 11:33

FromDual has the pleasure to announce the release of the new version 1.2.2 of the popular Backup Manager for MySQL and MariaDB (fromdual_bman).

You can download the FromDual Backup Manager from here.

In the inconceivable case that you find a bug in the Backup Manager please report it to our Bugtracker.

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

Upgrade from 1.2.x to 1.2.2 # cd ${HOME}/product # tar xf /download/fromdual_brman-1.2.2.tar.gz # rm -f fromdual_brman # ln -s fromdual_brman-1.2.2 fromdual_brman
Changes in FromDual Backup Manager 1.2.2 FromDual Backup Manager

It contains mainly fixes with brman catalog and physical backups.

You can verify your current FromDual Backup Manager version with the following command:

fromdual_bman --version
  • Archiving with physical backup bug fixed.
  • Connect replaced by OO style and error exit fixed.
  • Create catalog fixed.
  • Archivedir without archive option does not make sense.

Wir suchen Dich: MySQL/MariaDB DBA für FromDual Support

Shinguz - Mon, 2015-06-22 13:51
Taxonomy upgrade extras: jobDBAsupportWer sind wir?

FromDual ist das führende unabhängige Beratungs- und Dienstleistungsunternehmen für MySQL, Galera Cluster, MariaDB und Percona Server in Europa mit Hauptsitz in der Schweiz.

Unsere Kunden stammen hauptsächlich aus Europa und reichen vom kleinen Start-Up bis zur europäischen Top-500 Firma. Sie erhalten von uns Support bei Datenbank-Problemen, direkte Eingriffe als remote-DBA, Schulung für ihre DBAs und Entwickler sowie Beratung bei Architektur- und Design-Entscheidungen. Ausserdem entwickeln wir Tools rund um MySQL, schreiben Blog-Artikel und halten Vorträge bei Konferenzen.

Da unsere qualitativ guten Dienstleistungen immer mehr Kunden anziehen, brauchen wir Kollegen (m/w), welche selbst und mit uns wachsen wollen.

Stellenbeschreibung

Wir suchen deutschsprachige Mitarbeiter (Sie oder Ihn) auf Junior- oder Senior-Level für Dienstleistungen rund um MySQL (hauptsächlich Support und remote-DBA Arbeiten) in Vollzeit. Primär solltest Du sicherstellen, dass die geschäftskritischen MySQL-Datenbanken unserer Kunden wie am Schnürchen laufen - und falls nicht, diese schnell wieder ans Laufen kriegen...


Unser/e "Wunschkandidat/in"

  • hat Erfahrung im Betrieb kritischer und hoch verfügbarer produktiver Datenbanken hauptsächlich auf Linux,
  • kennt Replikation in allen Variationen aus der täglichen Arbeit,
  • weiß, wie die meist verbreiteten MySQL-HA-Setups funktionieren und wie man sie wieder effizient repariert, wenn ein Problem auftritt,
  • ist sattelfest in SQL,
  • bringt Erfahrung mit Galera Cluster mit,
  • kann Bash skripten und einfache Programme in mindestens einer verbreiteten Programmier-/Skripting-Sprache (PHP, Bash, ...) erstellen.

Wir suchen Verstärkung, die von soliden Grundlagen aus auf dem Weg zu diesem Ideal ist.


Was wir von Dir erwarten:

  • Kenntnisse in MySQL, Percona Server oder MariaDB oder Bereitschaft, sich diese anzueignen
  • wissen, wie man kritische Datenbank-Systeme betreibt
  • Verständnis, was beim Betrieb von Datenbanken falsch laufen kann
  • selbständige Arbeitsweise (remote) mit Kommunikation über IRC, Skype, Mail und Telefon
  • Kenntnisse des Linux Systems

DBA- oder DevOps-Erfahrungen wären z.B. eine gute fachliche Basis.


Du schätzt den direkten Kontakt mit Kunden, hast ein gutes Gespür für deren Probleme, kannst zuhören und findest schnell die eigentlichen Probleme. Du bist gewohnt, proaktiv zu handeln bevor etwas passiert, und führst den Kunden wieder auf den richtigen Pfad zurück.


Um Deine Arbeit erledigen zu können, arbeitest Du in einer europäischen Zeitzone. Deine Arbeitszeit kannst Du, der betrieblichen Situation entsprechend, flexibel gestalten. Wir erwarten, dass Du Deinen Beitrag zum Bereitschaftsdienst leistest. FromDual hat voraussichtlich keine Büroräumlichkeiten in Deinem Wohnort. Ein Umzug ist jedoch nicht notwendig: Wir ermöglichen Dir das Arbeiten von zu Hause aus oder unterstützen Dich bei der Suche einer geeigneten Arbeitsräumlichkeit in Deiner Nähe. Gute schriftliche und mündliche Englischkenntnisse sind erforderlich.

Was wir Dir bieten:
  • Deinen Leistungen angemessenes Gehalt.
  • Möglichkeit Dich zum Top MySQL-Datenbankspezialisten zu entwickeln.
  • Selbständiges Arbeiten.
  • Verantwortung für Deine Projekte und Kunden zu übernehmen.
  • Gute Kameradschaft im Team, sowie lockerer und angenehmer Umgang.
  • Stellenbezogene Weiterbildungsmöglichkeiten.
  • Teilnahme an Open Source Anlässen.
  • Arbeit von Deinem bevorzugten Wohnort aus.

Du solltest in der Lage sein, die meiste Zeit selbständig zu arbeiten, zu denken und zu handeln und Dir neues Wissen selbständig anzueignen (durch Web-Suche, die MySQL-Dokumentation, Ausprobieren, etc.). Solltest Du dennoch einmal nicht weiterkommen, werden Dir Deine Kollegen von FromDual gerne helfen.


Wenn Du jemanden brauchst, der Dir die ganze Zeit Dein Händchen hält, ist FromDual nicht die richtige Wahl.


Wie geht es weiter

Wenn Du an dieser Chance interessiert bist und Du denkst, dass Du die passende Kandidatin oder der passende Kandidat bist, würden wir uns freuen, von Dir zu hören. Wir wissen, dass niemand 100% auf diese Stellenbeschreibung passt!


Bitte schicke Deinen ungeschönten Lebenslauf mit Deinen Gehaltsvorstellungen an jobs@fromdual.com. Wenn Du mehr über diese Stelle erfahren oder wenn Du mit mir persönlich sprechen möchtest, ruf mich bitte an unter +41 79 830 09 33 (Oli Sennhauser, CTO). Bitte nur Bewerber, KEINE Headhunter!


Nachdem Du uns Deinen Lebenslauf zugeschickt hast, darfst Du Deine Fähigkeiten in einem kleinen MySQL-Test unter Beweis zu stellen. Nach bestandenem Test laden wir Dich für die finalen Interviews ein.

Controlling worldwide manufacturing plants with MySQL

Shinguz - Thu, 2015-05-14 21:43
Taxonomy upgrade extras: multi-source replicationmysql-replicationreplicationMulti-Master Replicationfan-in replicationrow filteringGTID

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 need different schemas. Some which should be replicated, some which should NOT be replicated:

CREATE DATABASE finance; CREATE TABLE finance.accounting ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `data` varchar(255) DEFAULT NULL, `ts` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`id`), KEY `data_rename` (`data`) ); CREATE DATABASE crm; CREATE TABLE crm.customer ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `data` varchar(255) DEFAULT NULL, `ts` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`id`), KEY `data_rename` (`data`) ); CREATE DATABASE erp; -- Avoid specifying Storage Engine here!!! CREATE TABLE erp.manufacturing_data ( id INT UNSIGNED NOT NULL AUTO_INCREMENT , manufacture_plant VARCHAR(32) , manufacture_info VARCHAR(255) , PRIMARY KEY (id) , KEY (manufacture_plant) ); CREATE TABLE erp.manufacturing_log ( id INT UNSIGNED NOT NULL AUTO_INCREMENT , manufacture_plant VARCHAR(32) , log_data VARCHAR(255) , PRIMARY KEY (id) , KEY (manufacture_plant) );
MySQL replication architecture

Before you start with such complicated MySQL set-ups it is recommended to make a little sketch of what you want to build:

Preparing the Production Master database (Prod M1)

To make use of all the new and cool features of MySQL we used the new GTID replication. First we set up a Master (Prod M1) and its fail-over System (Prod M2) in the customers Head Quarter:

# /etc/my.cnf [mysqld] binlog_format = row # optional log_bin = binary-log # mandatory, also on Slave! log_slave_updates = on # mandatory gtid_mode = on # mandatory enforce_gtid_consistency = on # mandatory server-id = 39 # mandatory

This step requires a system restart (one minute downtime).

Preparing the Production Master standby database (Prod M2)

On Master (Prod M1):

GRANT REPLICATION SLAVE ON *.* TO 'replication'@'192.168.1.%' IDENTIFIED BY 'secret'; mysqldump -u root --set-gtid-purged=on --master-data=2 --all-databases --triggers --routines --events > /tmp/full_dump.sql

On Slave (Prod M2):

CHANGE MASTER TO MASTER_HOST='192.168.1.39', MASTER_PORT=3306 , MASTER_USER='replication', MASTER_PASSWORD='secret' , MASTER_AUTO_POSITION=1; RESET MASTER; -- On SLAVE! system mysql -u root < /tmp/full_dump.sql START SLAVE;

To make it easier for a Slave to connect to its master we set a VIP in front of those 2 database servers (VIP Prod). This VIP should be used by all applications in the head quarter and also the filter engines.

Set-up filter engines (Filter BR and Filter CN)

To make sure every manufacturing plant sees only the data it is allowed to see we need a filtering engine between the production site and the manufacturing plant (Filter BR and Filter CN).

To keep this filter engine lean we use a MySQL instance with all tables converted to the Blackhole Storage Engine:

# /etc/my.cnf [mysqld] binlog_format = row # optional log_bin = binary-log # mandatory, also on Slave! log_slave_updates = on # mandatory gtid_mode = on # mandatory enforce_gtid_consistency = on # mandatory server-id = 36 # mandatory default_storage_engine = blackhole

On the production master (Prod M1) we get the data as follows:

mysqldump -u root --set-gtid-purged=on --master-data=2 --triggers --routines --events --no-data --databases erp > /tmp/erp_dump_nd.sql

The Filter Engines (Filter BR and CN) are set-up as follows::

-- Here we can use the VIP! CHANGE MASTER TO master_host='192.168.1.33', master_port=3306 , master_user='replication', master_password='secret' , master_auto_position=1; RESET MASTER; -- On SLAVE! system cat /tmp/erp_dump_nd.sql | sed 's/ ENGINE=[a-zA-Z]*/ ENGINE=blackhole/' | mysql -u root START SLAVE;

Do not forget to also create the replication user on the filter engines.

GRANT REPLICATION SLAVE ON *.* TO 'replication'@'192.168.1.%' IDENTIFIED BY 'secret';
Filtering out all non ERP schemata

We only want the erp schema to be replicated to the manufacturing plants, not the crm or the finance application. This we achieve with the following option on the filter engines:

# /etc/my.cnf [mysqld] replicate_do_db = erp replicate_ignore_table = erp.manufacturing_log
MySQL row filtering

To achieve row filtering we use TRIGGERS. Make sure they are not replicated further down the hierarchy:

SET SESSION SQL_LOG_BIN = 0; use erp DROP TRIGGER IF EXISTS filter_row; delimiter // CREATE TRIGGER filter_row BEFORE INSERT ON manufacturing_data FOR EACH ROW BEGIN IF ( NEW.manufacture_plant != 'China' ) THEN SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Row was filtered out.' , CLASS_ORIGIN = 'FromDual filter trigger' , SUBCLASS_ORIGIN = 'filter_row' , CONSTRAINT_SCHEMA = 'erp' , CONSTRAINT_NAME = 'filer_row' , SCHEMA_NAME = 'erp' , TABLE_NAME = 'manufacturing_data' , COLUMN_NAME = '' , MYSQL_ERRNO = 1644 ; END IF; END; // delimiter ; SET SESSION SQL_LOG_BIN = 0;

Up to now this would cause to stop replication for every filtered row. To avoid this we tell the Filtering Slaves to skip this error number:

# /etc/my.cnf [mysqld] slave_skip_errors = 1644
Attaching production manufacturing Slaves (Man BR M1 and Man CN M1)

When we have finished everything on our head quarter site. We can start with the manufacturing sites (BR and CN):

On Master (Prod M1):

mysqldump -u root --set-gtid-purged=on --master-data=2 --triggers --routines --events --where='manufacture_plant="Brazil"' --databases erp > /tmp/erp_dump_br.sql mysqldump -u root --set-gtid-purged=on --master-data=2 --triggers --routines --events --where='manufacture_plant="China"' --databases erp > /tmp/erp_dump_cn.sql

On the Manufacturing Masters (Man BR M1 and Man BR M2). Here we do NOT use a VIP because we think a blackhole storage engine is robust enough as master:

CHANGE MASTER TO master_host='192.168.1.43', master_port=3306 , master_user='replication', master_password='secret' , master_auto_position=1; RESET MASTER; -- On SLAVE! system cat /tmp/erp_dump_br.sql | mysql -u root START SLAVE;

The standby manufacturing (Man BR M2 and Man CN M2) database is created in the same way as the production manufacturing database on the master.

Testing replication from HQ to manufacturing plants

First we make sure, crm and finance is not replicated out and replication also does not stop (on Prod M1):

INSERT INTO finance.accounting VALUES (NULL, 'test data over VIP', NULL); INSERT INTO finance.accounting VALUES (NULL, 'test data over VIP', NULL); INSERT INTO crm.customer VALUES (NULL, 'test data over VIP', NULL); INSERT INTO crm.customer VALUES (NULL, 'test data over VIP', NULL); UPDATE finance.accounting SET data = 'Changed data'; UPDATE crm.customer SET data = 'Changed data'; DELETE FROM finance.accounting WHERE id = 1; DELETE FROM crm.customer WHERE id = 1; SELECT * FROM finance.accounting; SELECT * FROM crm.customer; SHOW SLAVE STATUS\G

The schema filter seems to work correctly. Then we check if also the row filter works correctly. For this we have to run the queries in statement based replication (SBR)! Otherwise the trigger would not fire:

use mysql INSERT INTO erp.manufacturing_data VALUES (NULL, 'China', 'Highly secret manufacturing info as RBR.'); INSERT INTO erp.manufacturing_data VALUES (NULL, 'Brazil', 'Highly secret manufacturing info as RBR.'); -- This needs SUPER privilege... :-( SET SESSION binlog_format = STATEMENT; -- Caution those rows will NOT be replicated!!! -- See filter rules for SBR INSERT INTO erp.manufacturing_data VALUES (NULL, 'China', 'Highly secret manufacturing info as SBR lost.'); INSERT INTO erp.manufacturing_data VALUES (NULL, 'Brazil', 'Highly secret manufacturing info as SBR lost.'); use erp INSERT INTO manufacturing_data VALUES (NULL, 'China', 'Highly secret manufacturing info as SBR.'); INSERT INTO manufacturing_data VALUES (NULL, 'Brazil', 'Highly secret manufacturing info as SBR.'); INSERT INTO manufacturing_data VALUES (NULL, 'Germany', 'Highly secret manufacturing info as SBR.'); INSERT INTO manufacturing_data VALUES (NULL, 'Switzerland', 'Highly secret manufacturing info as SBR.'); SET SESSION binlog_format = ROW; SELECT * FROM erp.manufacturing_data;
Production data back to head quarter

Now we have to take care about the production data on their way back to the HQ. To achieve this we use the new MySQL 5.7 feature called multi source replication. For multi source replication the replication repositories must be kept in tables instead of files:

# /etc/my.cnf [mysqld] master_info_repository = TABLE # mandatory relay_log_info_repository = TABLE # mandatory

Then we have to configure 2 replication channels from Prod M1 to their specific manufacturing masters over the VIP (VIP BR and VIP CN):

CHANGE MASTER TO MASTER_HOST='192.168.1.98', MASTER_PORT=3306 , MASTER_USER='replication', MASTER_PASSWORD='secret' , MASTER_AUTO_POSITION=1 FOR CHANNEL "manu_br"; CHANGE MASTER TO MASTER_HOST='192.168.1.99', MASTER_PORT=3306 , MASTER_USER='replication', MASTER_PASSWORD='secret' , MASTER_AUTO_POSITION=1 FOR CHANNEL "manu_cn"; START SLAVE FOR CHANNEL 'manu_br'; START SLAVE FOR CHANNEL 'manu_cn'; SHOW SLAVE STATUS FOR CHANNEL 'manu_br'\G SHOW SLAVE STATUS FOR CHANNEL 'manu_cn'\G

Avoid to configure and activate the channels on Prod M2 as well.

Testing back replication from manufacturing plants

Brazil on Man BR M1:

INSERT INTO manufacturing_log VALUES (1, 'Production data from Brazil', 'data');

China on Man CN M1:

INSERT INTO manufacturing_log VALUES (2, 'Production data from China', 'data');

For testing:

SELECT * FROM manufacturing_log;

Make sure you do not run into conflicts (Primary Key, AUTO_INCREMENTS). Make sure filtering is defined correctly!

To check the different channel states you can use the following command:

SHOW SLAVE STATUS\G or SELECT ras.channel_name, ras.service_state AS 'SQL_thread', ras.remaining_delay , CONCAT(user, '@', host, ':', port) AS user , rcs.service_state AS IO_thread, REPLACE(received_transaction_set, '\n', '') AS received_transaction_set FROM performance_schema.replication_applier_status AS ras JOIN performance_schema.replication_connection_configuration AS rcc ON rcc.channel_name = ras.channel_name JOIN performance_schema.replication_connection_status AS rcs ON ras.channel_name = rcs.channel_name ;
Troubleshooting Inject empty transaction

If you try to skip a transaction as you did earlier (SQL_SLAVE_SKIP_COUNTER) you will face some problems:

STOP SLAVE; ERROR 1858 (HY000): sql_slave_skip_counter can not be set when the server is running with @@GLOBAL.GTID_MODE = ON. Instead, for each transaction that you want to skip, generate an empty transaction with the same GTID as the transaction

To skip the next transaction you have find the ones applied so far:

SHOW SLAVE STATUS\G ... Executed_Gtid_Set: c3611091-f80e-11e4-99bc-28d2445cb2e9:1-20

then tell MySQL to skip this by injecting a new empty transaction:

SET SESSION GTID_NEXT='c3611091-f80e-11e4-99bc-28d2445cb2e9:21'; BEGIN; COMMIT; SET SESSION GTID_NEXT='AUTOMATIC'; SHOW SLAVE STATUS\G ... Executed_Gtid_Set: c3611091-f80e-11e4-99bc-28d2445cb2e9:1-21 START SLAVE;
Revert from GTID-based replication to file/position-based replication

If you want to fall-back from MySQL GTID-based replication to file/position-based replication this is quite simple:

CHANGE MASTER TO MASTER_AUTO_POSITION = 0;
MySQL Support and Engineering

If you need some help or support our MySQL support and engineering team is happy to help you.

Logging Galera Cluster conflicts

Shinguz - Sat, 2015-04-11 12:30
Taxonomy upgrade extras: logginggaleraclusterconflictdeadlockerror logerror

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 GLOBAL STATUS LIKE 'wsrep_local_%r_s'; +---------------------------+-------+ | Variable_name | Value | +---------------------------+-------+ | wsrep_local_cert_failures | 42 | | wsrep_local_bf_aborts | 13 | +---------------------------+-------+

Those values are indicators that some transactions (Galera write sets) did to not succeed and were aborted by Galera. In this case the paranoid logging helps to find, what exactly was aborted and possibly helps to find out, if this can or should be fixed:

150410 1:44:18 [Note] WSREP: cluster conflict due to certification failure for threads: 150410 1:44:18 [Note] WSREP: Victim thread: THD: 151856, mode: local, state: executing, conflict: cert failure, seqno: 30399304 SQL: UPDATE login SET lTsexpire = UNIX_TIMESTAMP(NOW()) + lTimeout WHERE lSessionId = 'va3ta7besku82k56ncv3bnhlj5' *** Priority TRANSACTION: TRANSACTION 464359568, ACTIVE 0 sec starting index read mysql tables in use 1, locked 1 1 lock struct(s), heap size 360, 0 row lock(s) MySQL thread id 4, OS thread handle 0x7f1c0916c700, query id 8190690 Update_rows_log_event::find_row(30399302) *** Victim TRANSACTION: TRANSACTION 464359562, ACTIVE 0 sec mysql tables in use 1, locked 1 2 lock struct(s), heap size 360, 1 row lock(s), undo log entries 1 MySQL thread id 151856, OS thread handle 0x7f1c09091700, query id 8190614 172.20.100.11 sam_angiz query end UPDATE login SET lTsexpire = UNIX_TIMESTAMP(now()) + lTimeout WHERE lSessionId = 'va3ta7besku82k56ncv3bnhlj5' *** WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 835205 page no 3 n bits 72 index `PRIMARY` of table `fromdual`.`login` trx table locks 1 total table locks 2 trx id 464359562 lock_mode X locks rec but not gap lock hold time 0 wait time before grant 0 150410 1:44:18 [Note] WSREP: cluster conflict due to high priority abort for threads: 150410 1:44:18 [Note] WSREP: Winning thread: THD: 4, mode: applier, state: executing, conflict: no conflict, seqno: 30399302 SQL: (null) 150410 1:44:18 [Note] WSREP: Victim thread: THD: 151856, mode: local, state: committing, conflict: no conflict, seqno: -1 SQL: UPDATE login SET lTsexpire = UNIX_TIMESTAMP(now()) + lTimeout WHERE lSessionId = 'va3ta7besku82k56ncv3bnhlj5'

In the above Galera conflict 2 login transactions where running at the same time. They both come with the same Session ID and want to update the expiry timestamp. Now how to solve or fix this:

  • First check, if this table has a Primary Key (tables without a PK causes full table scans which can last for long time, increasing the chance for conflicts).
  • Second check, if there is a (UNIQUE?) index on lSessionId. A missing index leads to full table scans which increases the chance for conflicts.
  • Third check WHY 2 logins from the same Session ID can arrive at the same time (within 1 second) on 2 different Galera nodes (Ajax requests, etc...). Try to avoid such situations.

Galera Cluster last inactive check and VMware snapshots

Shinguz - Sat, 2015-04-11 11:46
Taxonomy upgrade extras: galeravmwaresnapshot

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. You can imagine that access to resources in virtual machines is even harder (especially I/O) than on bare metal, so you will see this in virtual machines more often.

This is not a Galera specific issue (it just reports being stuck, other mysqld threads are equally stuck) so there is no configuration options for that. You simply must make sure that your system and mysqld are properly configured, that there is enough RAM (buffer pool not over provisioned), that there is swap, that there are proper I/O drivers installed on guest and so on.

Basically, Galera runs in virtual machines as well as well virtual machines approximates bare metal.

We were still suspecting that this is somehow VMware related. This week we had the chance to investigate... At 01:36 am node Galera2 lost connection to the Cluster and became NON-PRIMARY. This is basically a bad sign:

150401 1:36:15 [Warning] WSREP: last inactive check more than PT1.5S ago (PT5.08325S), skipping check 150401 1:36:15 [Note] WSREP: (09c6b2f2, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://192.168.42.2:4567 150401 1:36:16 [Note] WSREP: view(view_id(NON_PRIM,09c6b2f2,30) memb { 09c6b2f2,0 } joined { } left { } partitioned { ce6bf2e1,0 d1f9bee0,0 }) 150401 1:36:16 [Note] WSREP: view(view_id(NON_PRIM,09c6b2f2,31) memb { 09c6b2f2,0 } joined { } left { } partitioned { ce6bf2e1,0 d1f9bee0,0 }) 150401 1:36:16 [Note] WSREP: New COMPONENT: primary = no, bootstrap = no, my_idx = 0, memb_num = 1 150401 1:36:16 [Note] WSREP: Flow-control interval: [16, 16] 150401 1:36:16 [Note] WSREP: Received NON-PRIMARY. 150401 1:36:16 [Note] WSREP: Shifting SYNCED -> OPEN (TO: 26304132) 150401 1:36:16 [Note] WSREP: New COMPONENT: primary = no, bootstrap = no, my_idx = 0, memb_num = 1 150401 1:36:16 [Note] WSREP: Flow-control interval: [16, 16] 150401 1:36:16 [Note] WSREP: Received NON-PRIMARY. 150401 1:36:16 [Warning] WSREP: Send action {(nil), 328, TORDERED} returned -107 (Transport endpoint is not connected) 150401 1:36:16 [Note] WSREP: New cluster view: global state: dcca768c-b5ad-11e3-bbc0-fb576fb3c451:26304132, view# -1: non-Primary, number of nodes: 1, my index: 0, protocol version 3 150401 1:36:17 [Note] WSREP: (09c6b2f2, 'tcp://0.0.0.0:4567') reconnecting to d1f9bee0 (tcp://192.168.42.1:4567), attempt 0

I suspected, after some investigation with the FromDual Performance Monitor for MySQL and MariaDB, that the database backup (mysqldump) could be the reason. It was not. But the customer explained, that after the database backup they do a VMware snapshot.

And when we compared our problem with the backup log file:

2015/04/01 01:35:08 [3] backup.fromdual.com: Creating a snapshot of galera3 2015/04/01 01:35:16 [3] backup.fromdual.com: Created a snapshot of galera3 2015/04/01 01:35:23 [3] backup.fromdual.com: galera3: backup the changed blocks of disk 'Festplatte 1' using NBD transport 2015/04/01 01:36:10 [3] backup.fromdual.com: galera3: saving the Change Block Tracking's reference for disk 'Festplatte 1' 2015/04/01 01:36:10 [3] backup.fromdual.com: Removing Arkeia's snapshot of galera3

we can see that our problem pretty much started with the end of the WMware snapshot (01:36:10 + 5.08 = 1:36:15). By the way: For such kind of investigations it is always good to have a ntp daemon for time synchronization running. Otherwise problem investigation becomes much harder...

Some more and deeper investigation shows that we loose from time to time nodes during VMware snapshots (galera3). But they recover quickly because they can do an IST. In worst case we can loose 2 nodes and then the whole Galera Cluster has gone.

192.168.42.3 / node Galera3 2015-04-10 01:44:00 [3] backup.fromdual.com: Creating a snapshot of galera3 2015-04-10 01:44:08 [3] backup.fromdual.com: Created a snapshot of galera3 2015-04-10 01:44:15 [3] backup.fromdual.com: galera3: backup the changed blocks of disk 'Festplatte 1' using NBD transport 2015-04-10 01:45:39 [3] backup.fromdual.com: galera3: saving the Change Block Tracking's reference for disk 'Festplatte 1' 2015-04-10 01:45:39 [3] backup.fromdual.com: Removing Arkeia's snapshot of galera3
150410 1:44:07 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera1:4567 tcp://galera2:4567 150410 1:44:07 [Warning] WSREP: last inactive check more than PT1.5S ago (PT7.06159S), skipping check 150410 1:44:08 [Note] WSREP: Received NON-PRIMARY. 150410 1:44:10 [Note] WSREP: Shifting OPEN -> PRIMARY (TO: 30399299) 150410 1:44:11 [Warning] WSREP: Gap in state sequence. Need state transfer. 150410 1:44:11 [Note] WSREP: Prepared IST receiver, listening at: tcp://galera3:4568 150410 1:44:11 [Note] WSREP: Member 0.0 (galera3) requested state transfer from '*any*'. Selected 2.0 (galera2)(SYNCED) as donor. 150410 1:44:11 [Note] WSREP: Shifting PRIMARY -> JOINER (TO: 30399309) 150410 1:44:11 [Note] WSREP: Requesting state transfer: success, donor: 2 150410 1:44:11 [Note] WSREP: 2.0 (galera2): State transfer to 0.0 (galera3) complete. 150410 1:44:11 [Note] WSREP: Member 2.0 (galera2) synced with group. 150410 1:44:11 [Note] WSREP: Receiving IST: 8 writesets, seqnos 30399291-30399299 150410 1:44:11 [Note] WSREP: IST received: dcca768c-b5ad-11e3-bbc0-fb576fb3c451:30399299 150410 1:44:11 [Note] WSREP: 0.0 (galera3): State transfer from 2.0 (galera2) complete. 150410 1:44:11 [Note] WSREP: Shifting JOINER -> JOINED (TO: 30399309) 150410 1:44:11 [Note] WSREP: Member 0.0 (galera3) synced with group. 150410 1:44:11 [Note] WSREP: Shifting JOINED -> SYNCED (TO: 30399309) 150410 1:44:11 [Note] WSREP: Synchronized with group, ready for connections 150410 1:44:13 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') turning message relay requesting off 150410 1:45:42 [Warning] WSREP: last inactive check more than PT1.5S ago (PT2.47388S), skipping check 150410 1:45:43 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera1:4567 tcp://galera2:4567 150410 1:45:44 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') reconnecting to 54de92f8 (tcp://galera1:4567), attempt 0 150410 1:45:44 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') reconnecting to c9d964d3 (tcp://galera2:4567), attempt 0 150410 1:45:48 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') turning message relay requesting off 150410 1:47:26 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera1:4567 150410 1:47:27 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') reconnecting to 54de92f8 (tcp://galera1:4567), attempt 0 150410 1:47:31 [Note] WSREP: (158f71de, 'tcp://0.0.0.0:4567') turning message relay requesting off
192.168.42.1 / node Galera1 2015-04-10 01:47:24 [3] backup.fromdual.com: Creating a snapshot of galera1 2015-04-10 01:47:29 [3] backup.fromdual.com: Created a snapshot of galera1 2015-04-10 01:47:40 [3] backup.fromdual.com: galera1: backup the changed blocks of disk 'Festplatte 1' using NBD transport 2015-04-10 01:48:43 [3] backup.fromdual.com: galera1: saving the Change Block Tracking's reference for disk 'Festplatte 1' 2015-04-10 01:48:44 [3] backup.fromdual.com: Removing Arkeia's snapshot of galera1 150410 1:44:02 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera3:4567 150410 1:44:04 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') reconnecting to 158f71de (tcp://galera3:4567), attempt 0 150410 1:44:12 [Note] WSREP: Member 0.0 (galera3) requested state transfer from '*any*'. Selected 2.0 (galera2)(SYNCED) as donor. 150410 1:45:43 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera3:4567 150410 1:45:44 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') reconnecting to 158f71de (tcp://galera3:4567), attempt 0 150410 1:45:48 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') turning message relay requesting off 150410 1:47:27 [Warning] WSREP: last inactive check more than PT1.5S ago (PT3.66452S), skipping check 150410 1:47:27 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera3:4567 150410 1:47:30 [Note] WSREP: (54de92f8, 'tcp://0.0.0.0:4567') turning message relay requesting off
192.168.42.2 / node Galera2 2015-04-10 02:09:55 [3] backup.fromdual.com: Creating a snapshot of galera2 2015-04-10 02:09:58 [3] backup.fromdual.com: Created a snapshot of galera2 2015-04-10 02:10:05 [3] backup.fromdual.com: galera2: backup the changed blocks of disk 'Festplatte 1' using NBD transport 2015-04-10 02:10:53 [3] backup.fromdual.com: galera2: saving the Change Block Tracking's reference for disk 'Festplatte 1' 2015-04-10 02:10:54 [3] backup.fromdual.com: Removing Arkeia's snapshot of galera2
150410 1:44:02 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera3:4567 150410 1:44:03 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') reconnecting to 158f71de (tcp://galera3:4567), attempt 0 150410 1:44:08 [Warning] WSREP: discarding established (time wait) 158f71de (tcp://192.168.42.3:4567) 150410 1:44:11 [Note] WSREP: Member 0.0 (galera3) requested state transfer from '*any*'. Selected 2.0 (galera2)(SYNCED) as donor. 150410 1:44:13 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') turning message relay requesting off 150410 1:45:43 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera3:4567 150410 1:45:44 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') reconnecting to 158f71de (tcp://galera3:4567), attempt 0 150410 1:45:48 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') turning message relay requesting off 150410 1:47:26 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') turning message relay requesting on, nonlive peers: tcp://galera1:4567 150410 1:47:27 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') reconnecting to 54de92f8 (tcp://galera1:4567), attempt 0 150410 1:47:30 [Note] WSREP: (c9d964d3, 'tcp://0.0.0.0:4567') turning message relay requesting off 150410 2:09:57 [Warning] WSREP: last inactive check more than PT1.5S ago (PT1.83618S), skipping check

The backups are done with the 2 options:

enabled.

Possibly this is the reason and one should disable those features in combination with Galera. Further investigation is going on. In worst case VMware snapshotting with Galera should be avoided.

Rename MySQL Partition

Shinguz - Fri, 2015-03-06 15:00
Taxonomy upgrade extras: partitionrenameDDL

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 operation...

MySQL Partitioning was introduced in MySQL 5.1.

MySQL Enterprise Incremental Backup simplified

Shinguz - Wed, 2015-02-25 19:41
Taxonomy upgrade extras: mebMySQL Enterprise BackupenterpriseBackupincremental backup

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 know and we send you a quote...

Prepare MySQL Backup infrastructure mkdir /backup/full /backup/incremental1 /backup/incremental2
Full MySQL Backup mysqlbackup --defaults-file=/etc/my.cnf --user=root --backup-dir=/backup/full backup mysqlbackup --defaults-file=/etc/my.cnf --user=root --backup-dir=/backup/full apply-log
First MySQL Incremental Backup mysqlbackup --defaults-file=/etc/my.cnf --user=root --incremental --incremental-base=dir:/backup/full --incremental-backup-dir=/backup/incremental1 backup mysqlbackup --defaults-file=/etc/my.cnf --user=root --backup-dir=/backup/full --incremental-backup-dir=/backup/incremental1 apply-incremental-backup
Second MySQL Incremental Backup mysqlbackup --defaults-file=/etc/my.cnf --user=root --incremental --incremental-base=dir:/backup/full --incremental-backup-dir=/backup/incremental2 backup mysqlbackup --defaults-file=/etc/my.cnf --user=root --backup-dir=/backup/full --incremental-backup-dir=/backup/incremental2 apply-incremental-backup

and so on...

MySQL Restore mysqlbackup --defaults-file=/etc/my.cnf --user=root --backup-dir=/backup/full copy-back

Have fun with MySQL Enterprise Backup. If you need any help with your MySQL Backup concept, please let us know.

Creating Event Handlers with MySQL Enterprise Monitor

Shinguz - Tue, 2015-02-17 13:57
Taxonomy upgrade extras: MySQL Enterprise Monitormonitoringeventhandlermpmperformance monitor

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 which Advisors are available at all: Configuration -> Advisors -> Availability.


Here we can see that we have an Advisor called Maximum Connection Limit Nearing Or Reached which is scheduled for every 5 minutes and has thresholds at 75, 85, 95 and 100%:


Now we know which Advisor should create and Event. As a next step we have to create and Event which should be triggered: Configuration -> Event Handling -> Create Event Handler.


Here we can create and Event with all its needed configuration: Events -> All -> server.


If we look at the Events we can even see the detailed description and how the values for the Event are collected:


Task: Event Handler for used disk space

For this Event Handler we need the Advisor Filesystem Free Space under Operating System:


In this advisor we can configure the Threshold as well:


In the Event Handler we can define which Assets shall be monitored. For example the mountpoint: /.


Local disks can only be monitored, if a local MySQL Enterprise Monitor Agent is installed. An agent-less MySQL Enterprise Monitor cannot monitor local disk resources...

Have fun using the MySQL Enterprise Monitor. If you need any help in installing or configuring MEM do not hesitate to contact us.

All these functions are also implemented in the FromDual Performance Monitor for MySQL. If you want to relay on Open Source technology only you should consider our Performance Monitor.

Nagios and Icinga plug-ins for MySQL 1.0.0 have been released

Shinguz - Wed, 2015-02-04 22:02
Taxonomy upgrade extras: nagiosicingaplug-inmonitorperformancealert

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

All plug-ins are basically renewed and should now work all correctly.

The new Nagios/Icinga plug-ins can be downloaded here.

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

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

Description of the current functionality

Details about the functionality and the usage of each plug-in you get with the option: --help.

The following Nagios/Icinga plug-in for MySQL and MariaDB are currently available:

check_db_mysql.pl

This Nagios/Icinga plug-in alerts you if your MySQL database is not up and running.

check_errorlog_mysql.pl and errorLogFilterRules.pm

This Nagios/Icinga plug-in alerts you if it finds some suspicious messages in the MySQL error log.
The rules which messages should be ignored can be found in the file errorLogFilterRules.pm. If you want to add your own filter rules please add them in this file as well.

check_galera_nodes.pl

This Nagios/Icinga plug-in alerts you if the actual number of nodes in your a Galera Cluster is not the expected one.

check_repl_mysql_cnt_slave_hosts.pl

This Nagios/Icinga plug-in alerts you if your MySQL Slaves have not reported to their Master properly their existence with the report_host variable.

check_repl_mysql_heartbeat.pl

This Nagios/Icinga plug-in alerts you if your MySQL Slave is too many heartbeats behind its Master.

check_repl_mysql_io_thread.pl

This Nagios/Icinga plug-in alerts you if your MySQL Slaves IO thread is not up an running.

check_repl_mysql_read_exec_pos.pl

This Nagios/Icinga plug-in alerts you if your MySQL Slaves read and execution positions differ too much.

check_repl_mysql_readonly.pl

This Nagios/Icinga plug-in alerts you if your MySQL Slave is NOT set to readonly.

check_repl_mysql_seconds_behind_master.pl

This Nagios/Icinga plug-in alerts you if your MySQL Slave falls too many seconds behind its Master.

check_repl_mysql_sql_thread.pl

This Nagios/Icinga plug-in alerts you if your Slaves SQL thread is not up an running.

perf_mysql.pl

This Nagios/Icinga plug-in gathers MySQL and MariaDB performance data.

Changes in FromDual Nagios/Icinga plug-ins 1.0.0 All plug-ins
  • Usage was improved. The usage can be shown with the --help option.
  • Usage states now which GRANT privileges are needed for a specific plug-in.
  • Examples added how to use each plug-in.
  • Default socket location moved from /tmp/mysql.sock to /var/run/mysqld/mysqld.sock.
  • New host/socket convention implemented in all scripts similar to MySQL client tools.
  • -epn tag added for Icinga.
check_errorlog_mysql.pl
  • Some bugs fixed.
  • More filtering rules added.
  • Filtering rules separated into own file.
  • Entry point finding problem fixed.
check_repl_mysql_heartbeat.pl
  • Script name fixed.
check_db.pl
  • Unknown command problem with Galera Cluster caught.
  • mysqladmin ping removed and implemented in Perl.
Support and Subscription for commercial use

For subscriptions for commercial use of this software please get in contact with us.

Download MySQL Enterprise Features

Shinguz - Mon, 2015-02-02 21:47
Taxonomy upgrade extras: enterprise monitorBackupworkbenchenterprise

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 having hard requirements for restore times (MTTR).

Last implementation tests we did with a customer for an about 30 Gbyte database were:

 MEBmysqldumpBackup10 minutes18 minutesRestore12 minutes80 minutes

If you need our help implementing MySQL Enterprise Backup into your backup infrastructure please get in contact with us. MySQL Enterprise Backup also seamlessly integrates into the FromDual Backup Manager for MySQL.

MySQL Enterprise Monitor (MEM)

MySQL Enterprise Monitor (MEM) is an Enterprise Monitoring Solution for MySQL which Monitors your business critical MySQL databases. Various predefined advisors rise an alert if something with your precious MySQL database does not work as expected.

Our alternative competitive product is the FromDual Performance Monitor for MySQL.

MySQL Enterprise Workbench (MWB)

MySQL Enterprise Workbench (MWB) is the tool modern MySQL Database administrators use to operate their MySQL databases. Old fashion ones still use the CLI... MySQL developers can easily write and test database queries and develop their data model with the ER diagram modeller.

Download Enterprise tools

But how can we get now to these precious tools? This is quite easy following the screen shots below:

As a fist step you go to www.mysql.com/downloads:


Here you can find a link to Oracle eDelivery which is the MySQL/Oracle download facility. Then you get to the welcome screen:


Before you get access to the software you have to Sign In with your Oracle/MySQL customer account if you have one. If you do not have an account yet you can Create an Account to get to the software:


Then you have to agree (2 times) to the Terms & Restrictions (this is what Oracle is really good in). Once to the Oracle Trial License Agreement and once to the Export Restrictions:


Then you get to the Media Pack Search. Here you can define what product you are interested in and on which platform you are using it. Unfortunately a sub-product filter cannot be chosen. So you get a long list to pick your final package from:


An last you can download your product of desire:


Unfortunately the packages get some silly names like V59684-01.zip instead of meaningful names. But with the following command you get some information what is included in the package:

unzip -l V59684-01.zip Archive: V59684-01.zip Length Date Time Name --------- ---------- ----- ---- 2958631 2014-11-04 13:29 meb-3.11.1-linux-glibc2.5-x86-64bit.tar.gz 185 2014-11-05 08:30 meb-3.11.1-linux-glibc2.5-x86-64bit.tar.gz.asc 77 2014-11-04 13:29 meb-3.11.1-linux-glibc2.5-x86-64bit.tar.gz.md5 2130 2014-11-05 15:06 README.txt --------- ------- 2961023 4 files

Have fun trying the MySQL Enterprise Features. If you need any help installing or integrating them into your infrastructure, do not hesitate to contact FromDual.

MySQL table Point-in-Time-Recovery from mysqldump backup

Shinguz - Sun, 2015-01-25 19:42
Taxonomy upgrade extras: BackupRestoreRecoverymysqldumppoint-in-time-recoverypitr

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 dump and restore your table back to the production system. If you do it directly on your production system you have to know exactly what you are doing...
Further this process should be tested carefully and regularly to get familiar with it and to assure your backup/restore/recovery procedure works properly.

The table we want to recover is called test.test from our backup full_dump.sql.gz. As a first step we have to do the recovery with the following command to our test database:

shell> zcat full_dump.sql.gz | extract_table.py --database=test --table=test | mysql -u root

The script extract_table.py is part of the FromDual Recovery Manager to extract one single table from a mysqldump backup.

As a next step we have to extract the binary log file and its position where to start recovery from out of our dump:

shell> zcat full_dump.sql.gz | head -n 25 | grep CHANGE CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000216', MASTER_LOG_POS=1300976;

Then we have to find out where we want to stop our Point-in-Time-Recovery. The need for recover is possibly due to a TRUCATE TABLE command or similar operation executed on the wrong system or it is just a time somebody has indicated us to recover to. The position to stop we can find as follows:

shell> mysqlbinlog -v mysql-bin.000216 | grep -B5 TRUNCATE --color #150123 19:53:14 server id 35622 end_log_pos 1302950 CRC32 0x24471494 Xid = 3803 COMMIT/*!*/; # at 1302950 #150123 19:53:14 server id 35622 end_log_pos 1303036 CRC32 0xf9ac63a6 Query thread_id=54 exec_time=0 error_code=0 SET TIMESTAMP=1422039194/*!*/; TRUNCATE TABLE test

And as a last step we have to apply all the changes from the binary log to our testing database:

shell> mysqlbinlog --disable-log-bin --database=test --start-position=1300976 --stop-position=1302950 mysql-bin.000216 | mysql -u root --force

Now the table test.test is recovered to the wanted point in time and we can dump and restore it to its final location back to the production database.

shell> mysqldump --user=root --host=testing test test | mysql --user=root --host=production test

This process has been tested on MySQL 5.1.73, 5.5.38, 5.6.22 and 5.7.5 and also on MariaDB 10.0.10 and 10.1.0.

Impacts of max_allowed_packet size problems on your MySQL database

Shinguz - Sun, 2015-01-18 11:18
Taxonomy upgrade extras: max_allowed_packetconnectionBackupRestoredump

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; +----+--------------------------------+--------------+------+ | id | left(data, 30) | length(data) | ts | +----+--------------------------------+--------------+------+ | 1 | Anhang | 6 | NULL | | 2 | Anhang | 6 | NULL | | 3 | Anhangblablablablablablablabla | 2400006 | NULL | | 4 | Anhang | 6 | NULL | +----+--------------------------------+--------------+------+

Max_packet_size was set to a too small value then:

mysql> SHOW GLOBAL VARIABLES WHERE variable_name = 'max_allowed_packet'; +--------------------+---------+ | Variable_name | Value | +--------------------+---------+ | max_allowed_packet | 1048576 | +--------------------+---------+

The first test was to retrieve the too big row:

mysql> SELECT * FROM test WHERE id = 3; ERROR 2020 (HY000): Got packet bigger than 'max_allowed_packet' bytes mysql> SELECT CURRENT_USER(); ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 6 Current database: test

We got an error message AND we were disconnected from the server. This is indicated with the message MySQL server has gone away which is basically wrong. We were disconnected and not the server has died or similar in this case.

A further symptom is that we get an entry in the MySQL error log about this incident:

[Warning] Aborted connection 3 to db: 'test' user: 'root' host: 'localhost' (Got an error writing communication packets)

So watching carefully such error messages in your MySQL error log with the script check_error_log_mysql.pl from our Nagios/Icinga plugins would be a good idea...

The mysqldump utility basically does the same as a SELECT command so I tried this out and got the same error:

shell> mysqldump -u root test > /tmp/test_dump.sql mysqldump: Error 2020: Got packet bigger than 'max_allowed_packet' bytes when dumping table `test` at row: 2

And again we get an error message in the error log! This is also a good indicator to see if your backup, made with mysqldump failed in this case.

To get a proper dump we have to configure the mysqldump utility properly:

shell> mysqldump --max-allowed-packet=5000000 -u root test > /tmp/test_dump.sql

After the backup we tried to restore the data:

shell> mysql -u root test < /tmp/test_dump.sql ERROR 2006 (HY000) at line 40: MySQL server has gone away

Again we got an error on the command line and in the MySQL error log:

[Warning] Aborted connection 11 to db: 'test' user: 'root' host: 'localhost' (Got a packet bigger than 'max_allowed_packet' bytes)

and further the data are only partially loaded:

mysql> SELECT * FROM test; +----+--------+------+ | id | data | ts | +----+--------+------+ | 1 | Angang | NULL | | 2 | Angang | NULL | +----+--------+------+

Another symptom we can see here is that the MySQL status aborted_clients is increased in all 3 situation:

mysql> SHOW GLOBAL STATUS WHERE variable_name = 'aborted_clients'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | Aborted_clients | 10 | +-----------------+-------+

One positive aspect is that with MySQL 5.7.5 the first 2 symptoms do not appear any more...

Further information you can find here: Communication Errors and Aborted Connections.

Avoid temporary disk tables with MySQL

Shinguz - Fri, 2014-12-19 07:38
Taxonomy upgrade extras: temporary tablediskselectquery tuning

For processing SELECT queries MySQL needs some times the help of temporary tables. These temporary tables can be created either in memory or on disk.

The number of creations of such temporary tables can be found with the following command:

mysql> SHOW GLOBAL STATUS LIKE 'created_tmp%tables'; +-------------------------+-------+ | Variable_name | Value | +-------------------------+-------+ | Created_tmp_disk_tables | 4 | | Created_tmp_tables | 36 | +-------------------------+-------+
There are 2 different reasons why MySQL is creating a temporary disk table instead of a temporary memory table:
  • The result is bigger than the smaller one of the MySQL variables max_heap_table_size and tmp_table_size.
  • The result contains columns of type BLOB or TEXT.
In the following example we can see how the temporary disk table can be avoided without changing the column types: mysql> CREATE TABLE test ( id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY , data TEXT , type TINYINT UNSIGNED ); mysql> INSERT INTO test VALUES (NULL, 'State is green', 1), (NULL, 'State is green', 1) , (NULL, 'State is red', 3), (NULL, 'State is red', 3) , (NULL, 'State is red', 3), (NULL, 'State is orange', 2); mysql> EXPLAIN SELECT data, COUNT(*) FROM test GROUP BY data; +----+-------------+-------+------+---------------+------+---------+------+------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+---------------------------------+ | 1 | SIMPLE | test | ALL | NULL | NULL | NULL | NULL | 6 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+------+---------------------------------+ mysql> SHOW SESSION STATUS LIKE 'created_tmp%tables'; +-------------------------+-------+ | Variable_name | Value | +-------------------------+-------+ | Created_tmp_disk_tables | 0 | | Created_tmp_tables | 3 | +-------------------------+-------+ mysql> SELECT data, COUNT(*) FROM test GROUP BY data; +-----------------+----------+ | data | count(*) | +-----------------+----------+ | State is green | 2 | | State is orange | 1 | | State is red | 3 | +-----------------+----------+ mysql> SHOW SESSION STATUS LIKE 'created_tmp%tables'; +-------------------------+-------+ | Variable_name | Value | +-------------------------+-------+ | Created_tmp_disk_tables | 1 | | Created_tmp_tables | 4 | +-------------------------+-------+ mysql> SELECT SUBSTR(data, 1, 32), COUNT(*) FROM test GROUP BY SUBSTR(data, 1, 32); mysql> SHOW SESSION STATUS LIKE 'created_tmp%tables'; +-------------------------+-------+ | Variable_name | Value | +-------------------------+-------+ | Created_tmp_disk_tables | 1 | | Created_tmp_tables | 5 | +-------------------------+-------+

This method can be used if changing the table structure from TEXT to VARCHAR or the use of a RAM disk are not possible solutions.

Making HAProxy High Available for MySQL Galera Cluster

Shinguz - Sun, 2014-12-14 18:37
Taxonomy upgrade extras: HAProxyload balancerGalera ClusterVIPvirtual IPHigh Availabilityha

After properly installing and testing a Galera Cluster we see that the set-up is not finished yet. It needs something in front of the Galera Cluster that balances the load over all nodes.
So we install a load balancer in front of the Galera Cluster. Typically nowadays HAProxy is chosen for this purpose. But then we find, that the whole Galera Cluster is still not high available in case the load balancer fails or dies. So we need a second load balancer for high availability.
But how should we properly fail-over when the HAProxy load balancer dies? For this purpose we put a Virtual IP (VIP) in front of the HAProxy load balancer pair. The Virtual IP is controlled and fail-overed with Keepalived.

Installation of HAProxy and Keepalived

First some preparations: For installing socat we need the repoforge repository:

shell> cd /tmp shell> wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm shell> yum localinstall rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm shell> yum update shell> yum install socat

Then we can start installing HAProxy and Keepalived:

shell> yum install haproxy keepalived shell> chkconfig haproxy on shell> chkconfig keepalived on

We can check the installed HAProxy and Keepalived versions as follows:

shell> haproxy -v HA-Proxy version 1.5.2 2014/07/12 shell> keepalived --version Keepalived v1.2.13 (10/15,2014)
Configuration of HAProxy

More details you can find in the HAProxy documentation.

shell> cp /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.cfg.bak shell> cat << _EOF >/etc/haproxy/haproxy.cfg # # /etc/haproxy/haproxy.cfg # #--------------------------------------------------------------------- # Global settings #--------------------------------------------------------------------- global # to have these messages end up in /var/log/haproxy.log you will # need to: # # 1) configure syslog to accept network log events. This is done # by adding the '-r' option to the SYSLOGD_OPTIONS in # /etc/sysconfig/syslog # # 2) configure local2 events to go to the /var/log/haproxy.log # file. A line like the following can be added to # /etc/sysconfig/syslog # # local2.* /var/log/haproxy.log # log 127.0.0.1 local2 chroot /var/lib/haproxy pidfile /var/run/haproxy.pid maxconn 1020 # See also: ulimit -n user haproxy group haproxy daemon # turn on stats unix socket stats socket /var/lib/haproxy/stats.sock mode 600 level admin stats timeout 2m #--------------------------------------------------------------------- # common defaults that all the 'frontend' and 'backend' sections will # use if not designated in their block #--------------------------------------------------------------------- defaults mode tcp log global option dontlognull option redispatch retries 3 timeout queue 45s timeout connect 5s timeout client 1m timeout server 1m timeout check 10s maxconn 1020 #--------------------------------------------------------------------- # HAProxy statistics backend #--------------------------------------------------------------------- listen haproxy-monitoring *:80 mode http stats enable stats show-legends stats refresh 5s stats uri / stats realm Haproxy\ Statistics stats auth monitor:AdMiN123 stats admin if TRUE frontend haproxy1 # change on 2nd HAProxy bind *:3306 default_backend galera-cluster backend galera-cluster balance roundrobin server nodeA 192.168.1.61:5201 maxconn 151 check server nodeB 192.168.1.61:5202 maxconn 151 check server nodeC 192.168.1.61:5203 maxconn 151 check _EOF
Starting and testing HAProxy

The HAProxy can be started as follows:

shell> service haproxy start

and then be checked either over the socket:

shell> socat /var/lib/haproxy/stats.sock readline prompt > show info > show stat > help

or over your favourite web browser entering the username and password (monitor:AdMiN123) specified in the configuration file above:

To check the application over the load balancer we can run the following command:

shell> mysql --user=app --password=secret --host=192.168.1.38 --port=3306 --exec="SELECT @@wsrep_node_name;" +-------------------+ | @@wsrep_node_name | +-------------------+ | Node C | +-------------------+ shell> mysql --user=app --password=secret --host=192.168.1.38 --port=3306 --exec="SELECT @@wsrep_node_name;" +-------------------+ | @@wsrep_node_name | +-------------------+ | Node A | +-------------------+ shell> mysql --user=app --password=secret --host=192.168.1.38 --port=3306 --exec="SELECT @@wsrep_node_name;" +-------------------+ | @@wsrep_node_name | +-------------------+ | Node B | +-------------------+
Configuration a Virtual IP (VIP) with Keepalived

Now we have 2 HAProxy load balancers. But what happens if one of them fails. Then we do not want to reconfigure our application to work properly again. The fail-over should happen automatically. For this we need a Virtual IP which should automatically fail-over.

More details you can find in the Keepalived documentation and the keepalived user guide.

shell> cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak cat << _EOF >/etc/keepalived/keepalived.conf # # /etc/keepalived/keepalived.conf # global_defs { notification_email { remote-dba@fromdual.com root@localhost } # Change email from on lb2: notification_email_from lb1@haproxy1 router_id HAPROXY } vrrp_script chk_haproxy { script "killall -0 haproxy" interval 2 weight 2 } vrrp_instance GALERA_VIP { interface eth1 virtual_router_id 42 # Higher priority on other node priority 101 # 102 advert_int 1 # notify "/usr/local/bin/VRRP-notification.sh" virtual_ipaddress { 192.168.1.99/32 dev eth1 } track_script { chk_haproxy } authentication { auth_type PASS auth_pass secret } } _EOF
Starting and testing Keepalived

To test the keepalived we can run the following command:

shell> keepalived -f /etc/keepalived/keepalived.conf --dont-fork --log-console --log-detail ^C

To finally start it the following command will serve:

shell> service keepalived start

To check the Virtual IP the following command will help:

shell> ip addr show eth1

And then we can check our application over the VIP:

shell> mysql --user=app --password=secret --host=192.168.1.99 --port=3306 --exec="SELECT @@wsrep_node_name;"
Literature

failed MySQL DDL commands and Galera replication

Shinguz - Tue, 2014-12-09 15:45
Taxonomy upgrade extras: galerareplicationDDLTOIRSU

We have recently seen a case where the following command was executed on a Galera Cluster node:

SQL> GRANT SUPER ON userdb.* TO root@127.0.0.111; ERROR 1221 (HY000): Incorrect usage of DB GRANT and GLOBAL PRIVILEGES
2014-12-09 14:53:55 7457 [Warning] Did not write failed 'GRANT SUPER ON userdb.* TO root@127.0.0.111' into binary log while granting/revoking privileges in databases. 2014-12-09 14:53:55 7457 [ERROR] Slave SQL: Error 'Incorrect usage of DB GRANT and GLOBAL PRIVILEGES' on query. Default database: ''. Query: 'GRANT SUPER ON userdb.* TO root@127.0.0.111', Error_code: 1221 2014-12-09 14:53:55 7457 [Warning] WSREP: RBR event 1 Query apply warning: 1, 17 2014-12-09 14:53:55 7457 [Warning] WSREP: Ignoring error for TO isolated action: source: c5e54ef5-7faa-11e4-97b0-5e5c695f08a5 version: 3 local: 0 state: APPLYING flags: 65 conn_id: 4 trx_id: -1 seqnos (l: 4, g: 17, s: 15, d: 15, ts: 113215863294782)

According to the error message it looks like this command is done in Total Order Isolation (TOI) mode during the Rolling Schema Upgrade (RSU).

Only on the nodes which did NOT receive this wrong command the error log message was written and further they have received a GRA_*.log file.

Analysis of the GRA_*.log (failed transactions) files:

hexdump -C GRA_2_16.log 00000000 f3 fe 86 54 02 53 14 00 00 76 00 00 00 76 00 00 |...T.S...v...v..| 00000010 00 00 00 04 00 00 00 00 00 00 00 00 00 00 2a 00 |..............*.| 00000020 00 00 00 00 00 01 00 00 00 40 00 00 00 00 06 03 |.........@......| 00000030 73 74 64 04 21 00 21 00 08 00 0b 04 72 6f 6f 74 |std.!.!.....root| 00000040 09 6c 6f 63 61 6c 68 6f 73 74 00 67 72 61 6e 74 |.localhost.grant| 00000050 20 53 55 50 45 52 20 6f 6e 20 75 73 65 72 64 62 | SUPER on userdb| 00000060 2e 2a 20 74 6f 20 72 6f 6f 74 40 31 32 37 2e 30 |.* to root@127.0| 00000070 2e 30 2e 31 31 31 |.0.111 |
dd if=bin-log.000001 of=binlog.header bs=1 count=120 cat binlog.header GRA_2_17.log > GRA_2_17.binlog_events mysqlbinlog GRA_2_17.binlog_events ... # at 120 #141209 15:04:54 server id 5201 end_log_pos 118 CRC32 0x3432312e Query thread_id=45 exec_time=0 error_code=0 SET TIMESTAMP=1418133894/*!*/; SET @@session.pseudo_thread_id=4/*!*/; SET @@session.foreign_key_checks=1, @@session.sql_auto_is_null=0, @@session.unique_checks=1, @@session.autocommit=1/*!*/; SET @@session.sql_mode=1073741824/*!*/; SET @@session.auto_increment_increment=1, @@session.auto_increment_offset=1/*!*/; /*!\C utf8 *//*!*/; SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=8/*!*/; SET @@session.lc_time_names=0/*!*/; SET @@session.collation_database=DEFAULT/*!*/; grant SUPER on userdb.* to root@127.0.0.111 /*!*/; DELIMITER ; # End of log file ROLLBACK /* added by mysqlbinlog */; /*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/; /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;

It further looks like this command was issues by Connection ID number 4: conn_id: 4.

Get rid of wrongly deleted InnoDB tables

Shinguz - Wed, 2014-10-22 22:10
Taxonomy upgrade extras: BackupRestoreRecoveryinnodbtable

Precaution: Before you try this out on your production system do a BACKUP first! FromDual Backup Manager can help you with this.

Situation

A MySQL user has delete its InnoDB table files for example like this:

shell> rm -f $datadir/test/test.* Analysis

We do some analysis first:

mysql> DROP TABLE test; ERROR 1051 (42S02): Unknown table 'test' mysql> CREATE TABLE test (id INT) ENGINE = InnoDB; ERROR 1050 (42S01): Table '`test`.`test`' already exists

The MySQL error log shows us the following information:

141022 17:09:04 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: If you are installing InnoDB, remember that you must create InnoDB: directories yourself, InnoDB does not create them. 141022 17:09:04 InnoDB: Error: trying to open a table, but could not InnoDB: open the tablespace file './test/test.ibd'! InnoDB: Have you moved InnoDB .ibd files around without using the InnoDB: commands DISCARD TABLESPACE and IMPORT TABLESPACE? InnoDB: It is also possible that this is a temporary table #sql..., InnoDB: and MySQL removed the .ibd file for this. InnoDB: Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.5/en/innodb-troubleshooting-datadict.html InnoDB: for how to resolve the issue.
Fix

User claims that he does NOT need the table and/or the data any more but wants to get rid of the error messages and/or create a new table with the same name.

mysql> CREATE SCHEMA recovery; mysql> use recovery mysql> CREATE TABLE test (id INT) ENGINE = InnoDB; mysql> \! cp $datadir/recovery/test.frm $datadir/test/ mysql> DROP SCHEMA recovery; mysql> use test mysql> DROP TABLE test; Prove

To prove it works we create a new table and fill in some records:

mysql> CREATE TABLE test (id int UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, data VARCHAR(64), ts TIMESTAMP) ENGINE = InnoDB; mysql> INSERT INTO test VALUES (NULL, 'Test data', NULL); Literature

Migration between MySQL/Percona Server and MariaDB

Shinguz - Wed, 2014-10-08 21:40
Taxonomy upgrade extras: migrationsidegradeupgrademysqlmariadbpercona serverconversioncompatibility

This week we did some migrations from MariaDB 10.0 to Percona Server 5.6 at the IT department of a big German bank.

We were perfectly aware that since version 10.0 the MariaDB code base started to diverge slightly away from the MySQL and Percona Server code base which are still pretty close to each other.

Because of the Percona Server option enforce_storage_engine we wanted to do this migration.

We stopped the MariaDB 10.0 server replaced the binaries by the Percona Server 5.6 binaries and started the Percona 5.6 server again. After successfully starting the instance we found some error messages in the MySQL error log. By running the mysql_upgrade command some of the problems were fixed but not all of them. Still left problems were:

  • The MariaDB binary logs provoked some error messages for the Percona Server: [ERROR] Error in Log_event::read_log_event(): 'Found invalid event in binary log', data_len: 25, event_type: -93 [Warning] Error reading GTIDs from binary log: -1 [ERROR] Incorrect definition of table mysql.db: expected column 'User' at position 2 to have type char(16), found type char(80). [ERROR] Incorrect definition of table mysql.event: expected column 'definer' at position 3 to have type char(77), found type char(141). [ERROR] Incorrect definition of table mysql.event: expected column 'sql_mode' at position 14 to have type set... A purge of the binary logs solved this issue.
  • The tables mysql.event, mysql.innodb_table_stats and mysql.innodb_index_stats where not fixed by mysql_upgrade (a bug to fix for Percona and MySQL/Oracle?). We had to replace those tables manually by copying from an other already working Percona 5.6 Server.

Later in the FromDual technology labs we investigated further and tried the other way from Percona Server 5.6 to MariaDB 10.0. In this direction we found some other errors in the MySQL error log which also where not completely resolved by the mysql_upgrade utility:

  • The mysql.innodb_table_stats and mysql.innodb_index_stats tables where recreated manually (here a bug to fix for the MariaDB people?).
  • All error messages from tables affected by the following message: InnoDB: in InnoDB data dictionary has unknown flags 40/50/52. could be silenced by a run of the OPTIMIZE TABLE command (which can become quite expensive for very big tables).

Sidegrades from MySQL 5.6 to Percona Server 5.6 and back did not provoke any error message written to the MySQL log files. Sidegrades from MariaDB 10.0 to MySQL 5.6 and vice versa behaved exactly the same as MariaDB 10.0 to Percona Server 5.6 and back.

from/to: MySQL 5.6 MariaDB 10.0 Percona Server 5.6 MySQL 5.6 - 2 tables, OPTIMIZE OK MariaDB 10.0 binlog, 3 tables - binlog, 3 tables Percona Server 5.6 OK 2 tables, OPTIMIZE -

During our tests we got rid of the error messages. If they caused any technical harm to the tables or the data we cannot say so far. Further testing and experience from real life is needed. Any feedback is welcome!

Observations

It looks like MariaDB 10.0 understands MySQL/Percona Server replication but not the other way around. So replication from MariaDB 10.0 to MySQL 5.6 does probably not work (different implementation of GTID)?

Recommendation

To make sure a sigdegrade between these 3 MySQL branches/forks is seamlessly possible the best method seems to be to dump/restore (NOT xtrabackup!) the data. This can be an issue with huge databases (hundreds of Gbyte).

Further aid

Also have a look at our MySQL compatibility matrix and our MySQL upgrade check-list.

If you need any help to convert MySQL to MariaDB to Percona Server or the other way do not hesitate to contact the FromDual consultancy team. We will be pleased to assist you as a neutral and vendor independent consulting company.

Replication channel fail-over with Galera Cluster for MySQL

Shinguz - Thu, 2014-06-19 07:05
Taxonomy upgrade extras: channelgaleraclusterfail-overreplicationmasterslave

Sometimes it could be desirable to replicate from a Galera Cluster to a single MySQL slave or to an other Galera Cluster. Reasons for this measure could be:

  • An unstable network between two Galera Cluster locations.
  • A separation of a reporting slave and the Galera Cluster so that heavy reports on the slave do not affect the Galera Cluster performance.
  • Mixing different sources in a slave or a Galera Cluster (fan-in replication).

This article is based on earlier research work (see MySQL Cluster - Cluster circular replication with 2 replication channels) and uses the old MySQL replication style (without MySQL GTID).

Preconditions
  • Enable the binary logs on 2 nodes of a Galera Cluster (we call them channel masters) with the log_bin variable.
  • Set log_slave_updates = 1 on ALL Galera nodes.
  • It is recommended to have small binary logs and relay logs in such a situation to reduce overhead of scanning the files (max_binlog_size = 100M).
Scenarios

   

Let us assume that for some reason the actual channel master of channel 1 breaks. As a consequence the slave of channel 1 does not receive any replication events any more. But we have to keep the replication stream up and running. So we have to switch the replication channel to channel master 2.

Switching replication channel

First for security reasons we should stop the slave of replication channel 1 first:

mysql> STOP SLAVE;

Then we have to find the actual relay log on the slave:

mysql> pager grep Relay_Log_File mysql> SHOW SLAVE STATUS\G mysql> nopager Relay_Log_File: slave-relay-bin.000019

Next we have to find the last applied transaction on the slave:

mysql> SHOW RELAYLOG EVENTS IN 'slave-relay-bin.000019'; | slave-relay-bin.000019 | 3386717 | Query | 5201 | 53745015 | BEGIN | | slave-relay-bin.000019 | 3386794 | Table_map | 5201 | 53745067 | table_id: 72 (test.test) | | slave-relay-bin.000019 | 3386846 | Write_rows | 5201 | 53745142 | table_id: 72 flags: STMT_END_F | | slave-relay-bin.000019 | 3386921 | Xid | 5201 | 53745173 | COMMIT /* xid=1457451 */ | +------------------------+---------+-------------+-----------+-------------+--------------------------------+

This is transaction 1457451 which is the same on all Galera nodes.

On the new channel master of channel 2 we have to find now the matching binary log. This can be done best by matching times between the relay log and the binary log of master of channel 2.

On slave:

shell> ll *relay-bin* -rw-rw---- 1 mysql mysql 336 Mai 22 20:32 slave-relay-bin.000018 -rw-rw---- 1 mysql mysql 3387029 Mai 22 20:37 slave-relay-bin.000019

On master of channel 2:

shell> ll *bin-log* -rw-rw---- 1 mysql mysql 2518737 Mai 22 19:57 bin-log.000072 -rw-rw---- 1 mysql mysql 143 Mai 22 19:57 bin-log.000073 -rw-rw---- 1 mysql mysql 165 Mai 22 20:01 bin-log.000074 -rw-rw---- 1 mysql mysql 62953648 Mai 22 20:40 bin-log.000075

It looks like binary log 75 of master 2 matches to relay log of our slave.

Now we have to find the same transaction on the master of channel 2:

mysql> pager grep -B 6 1457451 mysql> SHOW BINLOG EVENTS IN 'bin-log.000075'; mysql> nopager | bin-log.000075 | 53744832 | Write_rows | 5201 | 53744907 | table_id: 72 flags: STMT_END_F | | bin-log.000075 | 53744907 | Xid | 5201 | 53744938 | COMMIT /* xid=1457450 */ | | bin-log.000075 | 53744938 | Query | 5201 | 53745015 | BEGIN | | bin-log.000075 | 53745015 | Table_map | 5201 | 53745067 | table_id: 72 (test.test) | | bin-log.000075 | 53745067 | Write_rows | 5201 | 53745142 | table_id: 72 flags: STMT_END_F | | bin-log.000075 | 53745142 | Xid | 5201 | 53745173 | COMMIT /* xid=1457451 */ | +----------------+----------+-------------+-----------+-------------+---------------------------------------+

We successfully found the transaction and want the position of the next transaction 53745173 where we should continue replicating.

As a last step we have to set the slave to the master of replication channel 2:

mysql> CHANGE MASTER TO master_host='master2', master_port=3306, master_log_file='bin-log.000075', master_log_pos=53745173; mysql> START SLAVE;

After a while the slave has caught up and is ready for the next fail-over back.

Discussion

We found during our experiments that an IST of a channel master does not lead to a gap or loss of events in the replication stream. So restarting a channel master does not require a channel fail-over as long as an IST can be used for resyncing the channel master with the Galera Cluster.

The increase of wsrep_cluster_conf_id is NOT an indication that a channel fail-over is required.

A SST resets the binary logs so after the SST a slave will not replicate any more. So using this method should be safe to use. If you find any situation where you experience troubles with channel fail-over please let us know.

Backup Manager for MySQL, MariaDB and Percona Server (mysql_bman)

Shinguz - Tue, 2014-05-06 17:28
Taxonomy upgrade extras: mysqlBackupRestoreRecoverymysql_bmanpitrAbout

The MySQL Backup Manager (mysql_bman) is a wrapper script for standard MySQL backup tools. The Problem with MySQL backup tools is, that they have many options and thus are overcomplicated and errors are easy made.

mysql_bman has the intention to make backups for MySQL easier and technically correct. This means it should per default not allow non-consistent backups or complain if some functions or parameters are used in the wrong way to guarantee proper backups.

In addition it has added some nice features which are missing in standard MySQL backup tools or which are only known from Enterprise backup solutions.

Where to download mysql_bman

The Backup Manager for MySQL (mysql_bman) can be downloaded from our website.

What mysql_bman user say about

Mathias Brem DBA@DBAOnline on LinkedIn:

Ow! Nice!
mysql backup manager is a very nice tool! Congratulations for FromDual! I made a shell script for catalog and maintained backups by xtrabackup, but mysql_bman is the best!

Xtrabackup + mysql_bman!!!!

Where can mysql_bman help you

The intention of mysql_bman is to assist you in bigger MySQL set-ups where you have to follow some backup policies and where you need a serious backup concept.

mysql_bman example

To give you an impression of the power of the MySQL Backup Manager let us have a look at a little example:

shell> mysql_bman --target=bman:secret@192.168.1.42 --type=full --mode=logical --policy=daily \ --no-compress --backupdir=/mnt/slowdisk \ --archive --archivedir=/mnt/nfsmount

With this backup method we do a logical full backup (mysqldump is triggered in the background). The backup is stored in the location for backups with the daily policy and is NOT compressed to speed up the backup by saving CPU power AND because the backup device is a de-duplicating drive. Then the backup is archived to and NFS mount.

Backup types

To achieve this we have defined different backup types:

TypeDescriptionfullfull logical backup (mysqldump) of all schemasbinlogbinary-log backupconfigconfiguration file backup (my.cnf)structurestructure backupcleanupclean-up of backup pieces older than n daysschemabackup of one or more schemasprivilegeprivilege dump (SHOW GRANTS FOR)

A backup type is specified with the option --type=<backup_type>.

Backup modes

A backup can either be logical or physical. A logical backup is typically what you do with mysqldump. A physical backup is typically a physical file copy without looking into the data. That is what for example xtrabackup does.

The backup mode is specified with the option --mode=<backup_mode>. The following backup modes are available:

ModeDescriptionlogicaldo a logical backup (mysqldump).physicaldo a physical backup (mysqlbackup/innobackup/xtrabackup)Backup policies

Further we have introduced different backup policies. Policies are there to distinguish how different backups should be treated.

The following backup policies exist:

PolicyDescriptiondailydirectory to store daily backupsweeklydirectory to store weekly backupsmonthlydirectory to store monthly backupsquarterlydirectory to store quarterly backupsyearlydirectory to store yearly backups

For example you could plan to do a daily MySQL backup with binary logs with a retention policy of 7 days. But once a week you want to do a weekly backup consisting of a full backup, a configuration backup and a structure dump. But this weekly backup you want to keep for 6 months. And because of legal reasons you want to do a yearly backup with a retention policy of 10 years.

A backup policy is specified with the --policy=<backup_policy> option. This leads us to the retention time:

Options

The retention time which should be applied to a specific backup policy you can specify with the option --retention=<period_in_days>. The retention option means that a backup is not deleted before this amount of days when you run a clean-up job with mysql_bman.

Let us do an example:

shell> mysql_bman --type=cleanup --policy=daily --retention=30

This means that all backups in the daily policy should be deleted when they are older than 30 days.

Target

With the --target option you specify the connect string to the database to backup. This database can be located either local (all backup types can be used) or remote (only client/server backup types can be used).

A target looks as follows: user/password@host:port (similar to URI specification) whereas you can omit password and port.

Backup location, archiving, compressing and clean-up

The --backupdir option is to control location of the backup files. The policy folders are automatically created under this --backupdir location.
If you have a second layer of backup stores (e.g. tapes or slow backup drives or deduplicated drives or NFS drives) you can use the --archive option to copy your backup files to this second layer storage which is specified with the --archivedir option. For restore performance reasons it is recommended to always keep one or two generations of backups on you fast local drive. If you want to remove the backuped files from the --backupdir destination after the archive job use the --cleanup option.
If you want to omit to compress backups, either to safe time or because your location uses deduplicated drives you can use the --no-compress option.

Per schema backup

Especially for hosting companies a full database backup is typically not the right backup strategy because a restore of one specific customer (= schema) is very complicated. For this case we have the --per-schema option. mysql_bman will do a backup of the whole database schema by schema. Keep in mind: This breaks consistency among schemas!

Sometimes you want to do a schema backup only for some specific schemas for this you can use the --schema option. This option allows you to specify schemas to backup or not to backup. --schema=+a,+b means backup schema a and b. --schema=-a,-b means backup all schemas except a and b.
The second variant is less error prone because you do not forget to backup a new database.

Instance name

MySQL does not know the concept of naming an instance (mysqld). But for bigger environments it could be useful to uniquely name each instance. For this purpose we have introduced the option --instance-name=<give_it_a_name>. This instance name should be unique within your whole company. But we do not enforce it atm. The instance name is used to name backup files and later to identify the backup history of an instance in our backup catalog and to allow us to track the files for restore.

mysql_bman configuration file

Specifying everything on the command line is cumbersome. Thus mysql_bman considers a configuration file specified with the --config=<config_file> option.
A mysql_bman configuration file looks for example as follows:

policy = daily target = root/secret@127.0.0.1:3306 type = schema schema = -mysql policy = daily archive = on archivedir = /mnt/tape per-schema = on no-compress = on
Simulate what happens

For the Sissies among us (as for example me) we have the --simulate option. This option simulates nearly all steps as far as possible without executing really anything. This option is either for testing some features or for debugging purposes.

Logging

If you want to track your backup history you can specify with the --log option where your mysql_bman log file should be located.

Using Catalog

It will be very useful when you can store your backups metadata in the database so you can check them in the future and to find out the backup criteria (type, mode, instance-name, ... etc) for specific backup processes. This could be achieved by using the catalog feature.

To activate this feature you have to create a database for the catalog "default name is bman_catalog" then create its tables by using the option --create in a special mysql_bman command (check examples below).
Finally, to store your backup metadata in the catalog what you only have to do is adding the option --catalog=catalog_connection_string to the normal mysql_bman command.
Check the examples below for using catalog in mysql_bman.

More help

A little more help you can get with the following command:

shell> mysql_bman --help
Examples

Do a full (logical = default) backup and store it in the daily policy folder:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=full --policy=daily

Do a full physical backup and store it in the weekly policy folder:

shell> mysql_bman --target=root/secret@127.0.0.1 --type=full --mode=physical --policy=weekly

Do a binary-log backup omitting the password in the target and store it in the daily policy folder:

shell> mysql_bman --target=bman@192.168.1.42:3307 --type=binlog --policy=daily

Do a MySQL configuration backup and store it in the weekly policy folder:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=config --policy=weekly

Do a structure backup and store it in the monthly policy folder and name the file with the instance name:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=structure --policy=monthly --instance-name=prod-db

Do a weekly structure backup and archive it to an other backup location:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=structure --policy=weekly --archive --archivedir=/mnt/tape

Do a schema backup omitting the mysql schema:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=schema --schema=-mysql --policy=daily --archive --archivedir=/mnt/tape

Do a schema backup only of foodmart and world and write it to their own files. Omit compressing these backups because they are located for example on deduplicated drives:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=schema --schema=+foodmart,+world --per-schema --policy=daily --no-compress

Creation of a backup catalog (assuming you have created already a catalog database with the default name "bman_catalog"):

shell> mysql_bman --catalog=root/secret@127.0.0.1:3306 --create

Backups against catalog:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --catalog=root/secret@127.0.0.1:3306 --instance-name=test --type=full --policy=daily

Privilege backup:

shell> mysql_bman --target=root/secret@127.0.0.1:3306 --type=privilege --policy=daily --mode=logical

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