Switching roles

To get a taste of the power of Tungsten Replicator, we will show how to switch roles. This is a controlled operation (as opposed to fail-over), where we can decide when to switch and which nodes are involved.

In our topology, host1 is the master, and we have three slaves. We can either ask for a switch and let the script select the first available slave, or tell the script which slave should be promoted. The script will show us the steps needed to perform the operation.

IMPORTANT! Please note that this operation is not risk free. Tungsten replicator is a simple replication system, not a complete management tool like Continuent Tungsten. WIth the replicator, you must make sure that the applications have stopped writing to the master before starting the switch, and then you should address the application to the new master when the …

Intro

Tungsten Replicator is an open source tool that does high performance replication across database servers. It was designed to replace MySQL replication, although it also supports replication from and to Oracle and other systems. In this article, we will only cover MySQL replication, both simple and multi-master.

Preparing for installation

To follow the material in this article, you will need a recent build of Tungsten Replicator. You can get the latest ones from http://bit.ly/tr20_builds. In this article, we are using build 2.0.8-167.

Before starting any installation, you should make sure that you have satisfied all the prerequisites. Don't underestimate the list. Any missing …

In the first part of this article we examined the types of conflicts and their causes. In this part, we will analyse some of the methods available to deal with conflicts.

Pessimistic locking (or: conflicts won't happen)

Applicability: synchronous clusters with 2pc

We've covered this topic in the previous article, but it's worth repeating. If you use a synchronous cluster, you don't have conflicts. For example, MySQL Cluster ensures consistent data with updates coming from different nodes. However, MySQL Cluster is not a replacement for a MySQL server, and it has severe limitations.

Optimistic locking

Applicability: synchronous clusters without 2pc (Galera)

Conflicting transactions proceed on different nodes with local locking. The last one then …

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 …

The Percona Live MySQL Conference and Expo 2013 is almost 1 month away. It's time to start planning, set the expectations, and decide what to attend. This post will give a roundup of some of the sessions that I recommend attending and I look forward to.

First, the unexpected!

After much talk and disbelief, here they come! Oracle engineers will participate to the Percona Live conference. This is wonderful! Their participation was requested by the organizers, by the attendees, and by community advocates, who all told the Oracle management how important it is to be in this conference. Finally, they have …

Stating the problem.

In my job, I do a lot of testing. And no matter how much organized we try to be, we end up with fewer machines than we would need to run all the tests that we want.

For some tasks, we can run MySQL Sandbox, and get the job done. But sometimes we need to make sure that applications and systems work well across the network, and we need to install and run systems on separate servers.

However, when you test replication systems, and every cluster takes three or four servers, you run our of available hosts very quickly. So you decide to use the clusters that are dedicated to automated testing to also run your own manual tests. Soon you realize that the tests that you are running manually are clashing with the automated ones, or with the ones that your colleagues are running.

A simple solution is installing additional sandboxes for the MySQL …

On Thursday, I will travel to Boston, MA, to attend the Northeast LinuxFest, which includes also an edition of the Open Database Camp. The events will be at one of my favorite places on earth: The Massachusetts Institute of Technology, a.k.a. the MIT. Every time I speak at an event there, I feel at home, and I look forward to be there once more.

The Open Database Camp is organized, as usual, with the formula of an un-conference, where the schedule is finalized on the spot.

There are a few ideas for sessions. I have proposed two of the topics I am most familiar with:

• …

Intro
While working on one of the MySQL to Oracle replication projects for Continuent, I needed to implement an open-source utility for transforming MySQL schema to an Oracle dialect (DDL statements that create specific schema on Oracle) to save from otherwise tedious work. This article introduces ./ddlscan tool, which does that and is extensible to do much more.

Ingredients
Here's what you'll need:

• Your favorite DBMS with some tables. Currently supported MySQL, Oracle and PostgreSQL.
• Latest Tungsten Replicator build. Not even needed to install, enough to untar.
• Velocity template of your choice. You will find …

MySQL 5.6 is probably the version of MySQL with the biggest bundle of new features. You may want to try it soon, since it's now released as GA, and I would like to offer some practical experience on how to use some of the advanced features.

Since replication is my main interest, I will focus on some of the new features in this field, and I will compare what's available in MySQL 5.6 with Tungsten Replicator.

The focus of the comparison is usability, manageability, and some hidden functionality. Parallel replication has been available with Tungsten Replicator for almost two years, and Global Transaction Identifiers for much longer than that. With MySQL 5.6, it seems that the MySQL team wants to close the gap. While the main feature (parallel execution threads) is available and performing well, there are some shocking differences in terms of ease of use, administration …

Tungsten Replicator 2.0.7 was released today. In addition to a large number of bug fixes, this release adds several improvements for multi-master management, and support for Amazon RDS (as a slave).

While the Release Notes show a long list of improvements, I would like to focus on some of them that improve the handling of multi-master deployments.

When we released version 2.0.6, we added the first revision of the cookbook recipes in the build. That was still a green addition, which caused several bug reports. But since then, we have integrated the cookbook in our internal testing, making these recipes more robust and reliable. We are also planning to improve them and eventually …