Introduction: where we standPrevious episodes:

• MySQL replication monitoring 101

MySQL replication in action - Part 1: GTID & Co
In the latest releases of MySQL and MariaDB we have seen several replication improvements. One of the most exciting additions is the ability to enhance basic replication with multiple sources. Those who have used replication for a while should remember that one of the tenets of the “old” replication was that a slave couldn’t have more than one master. This was The Law and there was no escape ... until now. The only way to work around that prohibition was to use circular replication, also known …

In the last 10 years I have worked a lot with replication systems, and I have developed a keen interest in the topic of multiple masters in a single cluster. My interest has a two distinct origins:

• On one hand, I have interacted countless times with users who want to use a replication system as a drop-in replacement for a single server. In many cases, especially when users are dealing with applications that are not much flexible or modular, this means that the replication system must have several points of data entry, and such points must work independently and in symbiosis with the rest of the nodes.
• On the other hand, I am a technology lover (look it up in the dictionary: it is spelled geek), and as such I get my curiosity stirred whenever I discover a new possibility of implementing multi-master systems.

The double nature of this professional curiosity makes me sometimes forget that the …

Replication is a hot topic in MySQL 5.6, and for good reason: There are many excellent features that make it a strong well-supported feature, from the new Global Transaction Identifiers (GTIDs), to simplified replication configuration and automated failover using MySQL Utilities (now available in alpha as a separate download).

Circular Replication

The simplest topology consists of a master server that accepts changes, and slaves that replicate those changes from the master. A common requirement is for a network to have multiple servers that accept changes and replicate to each other. This is possible by means of circular …

What is a conflict?

Readers of this blog know that one of my favorite tools, Tungsten Replicator, can easily create multi-master replication topologies, such as all-masters, star, fan-in. While this is good news for system designers and ambitious DBAs, it also brings some inconvenience. When you allow updates to happen in more than one master, you risk having conflicts. You may have heard this term before. For the sake of clarity, let's define what conflicts are, before analyzing each case in detail.

You have a conflict when several sources (masters) update concurrently the same data in asynchronous replication.

It's important to stress that this happens with asynchronous replication. In a truly synchronous cluster, where all data is kept consistent through 2-phase …

I have been working with MySQL replication for quite a while. I have dealt with simple replication setups and I have experimented with complex ones. Five years ago I wrote an article about advanced MySQL replication, which was mostly a dream on what you could do with imagination and skill, but the matter from that article is still not even remotely ready for production. Yet, since that article, I have been approached by dozens of people who wanted to know how to make the multiple master dream become reality. To all of them, I had to say, "sorry, this is just a proof of concept.Come back in a few years, it may become possible". It still isn't.
Despite its latest great technological advance, MySQL native replication is is very poor of topologies. What you can do with MySQL native replication is master-to-slave (which also includes relayed …

• A reader of that article told me that he used information I wrote to set up a circular replication in production, and it is still working!
• A new page on circular replication in MySQL manual was just published.
• During yesterday's meetup in New York, an attendee asked advice about broken replication in a circular scheme, and I suggested reading all the …