Replication on FromDual GmbH

Attribute promotion and demotion in the MariaDB Galera Cluster

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 28 Nov 2025 16:26:48 +0000

In MariaDB master/slave replication there is a feature called attribute promotion/demotion.

MariaDB's parallel replication to catch up

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 09 Apr 2024 10:53:32 +0000

Due to an application error, our replication stopped for 5 days (over Easter). After the problem was solved, the replication was supposed to catch up, which turned out to be very slow. All the usual tricks (innodb_flush_log_at_trx_commit, sync_binlog, etc.) had already been exhausted. So we tried our hand at parallel replication of the MariaDB server.

MariaDB MaxScale Load Balancer with Master/Master Replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 13 May 2022 16:39:27 +0000

For this how-to we were working with a MariaDB 10.6.5 database server and the newest MariaDB MaxScale 6.3.0 (aka 2.6) load balancer/proxy.

Learning from the Bugs Database

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 20 Jan 2022 15:05:52 +0000

This week I came across an old known issue reported in May 2010: Master/Slave Replication with binlog_format = ROW and tables without a Primary Key is a bad idea! Especially if these tables are huge.

MariaDB Push Replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 11 Jan 2021 17:29:50 +0000

How to make MariaDB Pull Replication as secure as possible

A normal MariaDB Replication is a Pull Replication. This means that a Slave connects to its Master and gathers or better requests Binary Log information from the Master and applies them in a streaming way.

MariaDB and MySQL Character Set Conversion

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 17 Aug 2019 21:50:15 +0000

Introduction

Recently we had a consulting engagement where we had to help the customer to migrate from latin1 Character Set to utf8mb4 Character Set. In the same MySQL consulting engagement we considered to upgrade from MySQL 5.6 to MySQL 5.7 as well
[ Lit.
]. We decided to split the change in 2 parts: Upgrading to 5.7 in the first step and converting to uft8mb4 in the second step. There were various reasons for this decision:

MariaDB Master/Master GTID based Replication with keepalived VIP

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 11 Nov 2017 11:29:29 +0000

Important: FromDual does NOT recommend to use an automated VIP failover technology as described below for a MariaDB/MySQL Master/Master Replication. In such a topology we recommend a manual VIP failover with prepared scripts!

How the Lack of a Primary Key May Effectively Stop the Slave

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 02 May 2017 09:50:52 +0000

Most (relational) DBAs and DB application developers know the concept of a primary key (“PK”) and what it is good for. However, much too often one still encounters table definitions without a PK. True, the relational theory based on sets does not need a PK, and all operations (insert, select, update, delete) can also be done on tables for which no PK was defined. If performance doesn’t matter (or the data volume is small, a typical situation in tests), the lack of a PK does not immediately cause negative consequences.

MySQL replication with filtering is dangerous

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 12 Jan 2017 16:47:53 +0000

From time to time we see in customer engagements that MySQL Master/Slave replication is set-up doing schema or table level replication filtering. This can be done either on Master or on Slave. If filtering is done on the Master (by the binlog_{do|ignore}_db settings), the binary log becomes incomplete and cannot be used for a proper Point-in-Time-Recovery. Therefore FromDual recommends AGAINST this approach.

Why is varchar(255) not varchar(255)?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 24 Jun 2016 16:18:43 +0000

Recently I was working on a clients question and stumbled over an issue with replication and mixed character sets. The client asked, wether it is possible to replicate data to a table on a MySQL slave, where one column had a different character set, than the column in the same table on the master.

Replication in a star

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 21 Jan 2016 21:24:28 +0000

Most of you know, that it is possible to synchronize MySQL and MariaDB servers using replication. But with the latest releases, it is also possible to use more than just two servers as a multi-master setup.

Binlog format MIXED with filtering

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 15 Jul 2015 06:11:36 +0000

Binlog format MIXED changes the binary log format (ROW or STATEMENT) depending on the queries (deterministic or not). This makes it impossible to define 100% correctly working binary log filter rules.

Controlling worldwide manufacturing plants with MySQL

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 14 May 2015 21:43:03 +0000

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.

failed MySQL DDL commands and Galera replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 09 Dec 2014 15:45:23 +0000

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

Things you should consider before using GTID

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 14 Nov 2014 16:50:19 +0000

Global Transaction ID (GTID) is one of the major features that were introduced in MySQL 5.6 which provides a lot of benefits. I have talked about the GTID concept, implementation and possible troubleshooting at Percona Live London 2014, you can download the slides from our presentations repository or from my session at Percona Live.

Replication Troubleshooting - Classic VS GTID

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 04 Jul 2014 15:05:58 +0000

In previous posts, I was talking about how to set up MySQL replication, Classic Replication (based on binary logs information) and Transaction-based Replication (based on GTID). In this article I’ll summarize how to troubleshoot MySQL replication for the most common issues we might face with a simple comparison how can we get them solved in the different replication methods (Classic VS GTID).

Replication channel failover with Galera Cluster for MySQL

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 19 Jun 2014 07:05:38 +0000

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:

GTID In Action

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 12 Jun 2014 14:09:05 +0000

In a previous post I was talking about How to Setup MySQL Replication using the classic method (based on binary logs information). In this article I’ll go through the transaction-based replication implementation using GTID in different scenarios.

How to Setup MySQL Master/Slave Replication ?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 24 Apr 2014 15:53:07 +0000

It’s not usual to find an easy source on how to setup MySQL replication, I thought it might be useful at least for the beginners to write a direct and simple howto blog on setting up Master/Slave replication in MySQL using the classic method (binary log information). Check out my post GTID In Action for information about transaction-based replication using GTID.

Galera Cluster for MySQL

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 11 Dec 2013 12:08:32 +0000

Features

Galera is a synchronous multi-master replication Cluster for MySQL/InnoDB databases, having features like:

Check and fix MySQL Replication inconsistencies

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 05 Dec 2013 11:56:08 +0000

There are many different possibilities how you can achieve inconsistencies between Master and Slave in a MySQL replication, intentional and non-intentional ones. How to achieve them is not the topic of this article.

Galera Cluster discussions at FrOSCon 2012

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 27 Aug 2012 17:18:40 +0000

During and after Henriks great talk about Galera Cluster at the FrOSCon 2012 in St. Augustin we found 2 important things related to Galera Cluster for MySQL:

SchoonerSQL

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 02 Aug 2012 14:59:20 +0000

There is a product out in the wild which is called SchoonerSQL
[ 1
] from an American company called Schooner Information Technology
[ 2
]. They claim to have top-performance
[ 3
] and high-availability features with up 99.999% availability
[ 1
].
The technology seems to be based on InnoDB, SSD and some kind of replication with failover mechanism.

DOAG SIG MySQL - Replication: September 4, 2012 in Hamburg

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 30 Jul 2012 15:11:17 +0000

On Tuesday, September 4, 2012 the next DOAG SIG MySQL meeting will take place in Hamburg (Germany) with the topic Replication.

Migrating from MySQL Master-Master Replication to Galera Multi-Master Replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 02 Dec 2011 14:48:58 +0000

Introduction

Galera is a synchronous Multi-Master Replication for MySQL. It is therefore in competition with several other MySQL architectures:

Building Galera Replication from Scratch

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 13 Nov 2011 12:29:54 +0000

Introduction

MySQL/Galera synchronous Multi-Master Replication consists of 2 parts:

The wsrep patches for MySQL (codership-mysql) and
the Galera Replication Plugin (galera).

If you do not want to download the prepared binaries you can build it on you own.
First you have to download the native MySQL sources, then patch it with the Galera wsrep patches and compile it. In a second step you have to build the Galera Plugin.

Galera - Synchronous Multi-Master Replication Cluster for MySQL/InnoDB

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 23 Sep 2011 11:07:03 +0000

Galera features

Galera provides the following features:

Synchronous replication
Active/active multi-master topology
Read and write to any cluster node
Automatic membership control, failed nodes drop from the cluster
Automatic node joining
True parallel row level replication
Direct client connections
Drop-in replacement for native MySQL

Galera benefits

Benefits using Galera Replication:

Be cautious when using Virtualized System with your Database

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 08 Jun 2011 15:01:29 +0000

A customer rose a support case with a problem on his Master-Master set-up. The 2^nd Master claims to have a problem:

MySQL Cluster - Cluster circular replication with 2 replication channels

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 10 Jan 2011 22:30:52 +0000

A few days ago I had to deal with MySQL Cluster replication. I did not do this for a while so I was prepared to expect some interesting surprises once again.

MariaDB, Galera and MySQL Support

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 01 Dec 2010 12:26:19 +0000

FromDual is a support partner of MariaDB plc, Codership Oy and Oracle Corporation. This gives us the opportunity to offer you customized enterprise support subscriptions for your mission-critical MariaDB, Galera or MySQL databases for all three vendors.

MySQL Multi-Master – Single-Slave – Replication (Episode 2)

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 13 Oct 2008 16:17:00 +0000

Introduction

One of the features that make MySQL so great is its easy replication set-up. If you are experienced and know-how to do it, it takes you about 15 minutes to set-up a slave. What you have in the end is a replication from one master to one or several slaves. So you can build a top-down data stream pyramid and spread your data on many slaves.

Active/active failover cluster with MySQL Replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 05 Sep 2008 17:00:00 +0000

Electing a slave as new master and aligning the other slaves to the new master

In a simple MySQL Replication set-up you have high-availability (HA) on the read side (r). But for the master which covers all the writes (w) and the time critical read (rt) there is no HA implemented. For some situations this can be OK. For example if you have rarely writes or if you can wait until a new Master is set up.

My thoughts about MySQL (Cluster) replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 28 Jun 2008 13:00:00 +0000

According to Johans wishes I write down my concerns about MySQL (Cluster) replication. These items are things I run again and again into it with customers:

MySQL Multi-Master - Single-Slave - Replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 21 Dec 2006 16:39:00 +0000

MySQL provides its replication for High Availability (HA) and for read Scale-out. Generally it is known that in a MySQL replication you can only replicate from one Master to many slaves. In this paper it is shown how a set-up can look like to replicate from two masters to one slave.

MySQL Binary Log Filter does not work

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 21 Oct 2015 05:23:36 +0200

Problem

We use the following binary log filter for filtering out some schemata.

MySQL Replication Slave is lagging more and more

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 18 Sep 2015 05:36:36 +0200

Problem

My MySQL Replication Slave is lagging more and more and I have no clue why. This happens since last weekends application change. I see that one Core is running at 100% user time but the I/O system is nearly completely idle. Any help is appreciated!

MySQL Replication Slave with corrupt Relay Logs

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 19:19:36 +0200

Problem

MySQL Replication Slave stuck because its disk run full. After restarting the Slave MySQL replication was broken with the following error:

MariaDB and MySQL PERFORMANCE_SCHEMA Hints

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 14 Jul 2013 09:29:09 +0200

Accounts not properly closing connections
Unused indexes
Who created temporary (disk) tables
Accounts which never connected since last start-up
Users which never connected since last start-up
Totally unused accounts (never connected since last restart and not used to check Stored Program or View privileges) since last start-up
SHOW FULL PROCESSLIST
Storage Engines per schema
Tables without a Primary Key
Bad SQL queries of users
SHOW PROFILE in PERFORMANCE_SCHEMA
SELECT, INSERT, UPDATE and DELETE per table
Top long running queries
Tables never written to
DML, DDL and DCL per account
Finding syntactically wrong/erroneous MySQL queries
Finding queries served by MySQL Query Cache
Grant access to sys schema to another user
Grant access to PERFORMANCE_SCHEMA schema to another user
Find InnoDB Locks
Find Metadata Locks
What did a Connection before sleeping?
How many statements did another (sleeping) connection?
MyISAM locking
Connections per user
Connections per user and IP
Accounts which could not connect or with connection errors
Temporary tables filling my disk
Who is writing to the binary log
Average binlog transaction size
Result size of SELECT statement
Find open long running transactions

MariaDB

On MariaDB you have to enable the Performance Schema first before use:

Replication on FromDual GmbH

Attribute promotion and demotion in the MariaDB Galera Cluster

MariaDB's parallel replication to catch up

MariaDB MaxScale Load Balancer with Master/Master Replication

Learning from the Bugs Database

MariaDB Push Replication

Table of Contents

How to make MariaDB Pull Replication as secure as possible

MariaDB and MySQL Character Set Conversion

Table of Contents

Introduction

MariaDB Master/Master GTID based Replication with keepalived VIP

How the Lack of a Primary Key May Effectively Stop the Slave

MySQL replication with filtering is dangerous

Why is varchar(255) not varchar(255)?

Replication in a star

Binlog format MIXED with filtering

Controlling worldwide manufacturing plants with MySQL

failed MySQL DDL commands and Galera replication

Things you should consider before using GTID

Replication Troubleshooting - Classic VS GTID

Replication channel failover with Galera Cluster for MySQL

GTID In Action

How to Setup MySQL Master/Slave Replication ?

Galera Cluster for MySQL

Features

Check and fix MySQL Replication inconsistencies

Galera Cluster discussions at FrOSCon 2012

SchoonerSQL

DOAG SIG MySQL - Replication: September 4, 2012 in Hamburg

Migrating from MySQL Master-Master Replication to Galera Multi-Master Replication

Introduction

Building Galera Replication from Scratch

Introduction

Galera - Synchronous Multi-Master Replication Cluster for MySQL/InnoDB

Galera features

Galera benefits

Be cautious when using Virtualized System with your Database

MySQL Cluster - Cluster circular replication with 2 replication channels

MariaDB, Galera and MySQL Support

MySQL Multi-Master – Single-Slave – Replication (Episode 2)

Introduction

Active/active failover cluster with MySQL Replication

Electing a slave as new master and aligning the other slaves to the new master

My thoughts about MySQL (Cluster) replication

MySQL Multi-Master - Single-Slave - Replication

MySQL Binary Log Filter does not work

Problem

MySQL Replication Slave is lagging more and more

Problem

MySQL Replication Slave with corrupt Relay Logs

Problem

MariaDB and MySQL PERFORMANCE_SCHEMA Hints

Table of Contents

MariaDB