When you have multiple database servers working together as nodes in a cluster, it’s beneficial to understand how data consistency is established. In this post, we’re going to take a look at the various cluster consistency levels that you can choose from within InnoDB Group Replication and see how they impact data flow and failure recovery.

Let’s start with a quick refresher on what data consistency is. In a nutshell, consistency is just a way of thinking about how data is duplicated across multiple nodes in a cluster. If you write a row of data to one node, that data is not considered to be consistent within the cluster until it has been written to all of the other participating nodes. Without consistency, it’s possible to write data to one node in the cluster but not see it immediately when reading from another node in the cluster. In some cases, the aforementioned scenario, better known as eventual consistency, is acceptable but …

The problem

In PXC 5.6 and 5.7, when using xtrabackup-v2 as the SST method, the DBA must create a user with the appropriate privileges for use by Percona XtraBackup (PXB). The username and password of this backup user are specified in the wsrep_sst_auth variable.

This is a problem because this username and password was being stored in plaintext and required that the configuration file be secured.

The PXC 8.0 solution

(This feature is still under development and may change before PXC 8.0 GA)

Because the wsrep_sst_auth is only needed on the donor side to take a backup, PXC 8.0 uses an internal user (created specifically for use by PXC) with a randomly generated password. Since this user is only needed on the donor, the plaintext password is not needed on the joiner …

Percona is happy to announce the first experimental binary of Percona XtraDB Cluster 8.0 on October 1, 2019. This is a major step for tuning Percona XtraDB Cluster to be more cloud- and user-friendly. This release combines the updated and feature-rich Galera 4, with substantial improvements made by our development team.

Improvements and New Features

Galera 4, included in Percona XtraDB Cluster 8.0, has many new features. Here is a list of the most essential improvements:

• Streaming replication supports large transactions
• The synchronization functions allow action coordination (wsrep_last_seen_gtid, wsrep_last_written_gtid, wsrep_sync_wait_upto_gtid)
• More granular and improved error logging. wsrep_debug is now a multi-valued variable to assist in controlling the logging, and logging messages have been significantly improved.
…

Overview

Clustering provides high availability and disaster recovery, along with the ability to read-scale both locally and globally. Some clusters even provide active/active capabilities, which others have a single master.

Real time database replication is a must for clustering and other key business purposes, like reporting. There are a number of replication technologies available for MySQL, and some are even bundled into various solutions. When choosing a replication methodology, it is paramount to understand just how the data moves from source to target. In this blog post, we will examine how asynchronous, synchronous, and “semi-synchronous” replication behave when used for clustering. Also, we will explore how …

Percona is happy to announce the release of Percona XtraDB Cluster 5.7.27-31.39 on September 18, 2019. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.7.27-31.39 is now the current release, based on the following:

• Percona Server for MySQL 5.7.27-30
• Codership WSREP API release 5.7.27
• Codership Galera library 3.28

All Percona software is open-source and free.

Bugs Fixed

• PXC-2432: PXC was not …

Percona is glad to announce the release of Percona XtraDB Cluster 5.6.45-28.36 on September 17, 2019. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.6.45-28.36 is now the current release, based on the following:

• Percona Server 5.6.45-86.1
• Codership WSREP API release 5.6.44
• Codership Galera library 3.28

All Percona software is open-source and free.

Bugs Fixed

• PXC-2432: PXC was not updating …

When we explore strategies to scale our MySQL-based database layer, we realize that there are many different options. As opposed to proprietary solutions, open-source products nourish themselves from their communities and novel architectures or enhanced versions are generated, often incorporating other open source technologies. MySQL is not an exception.

Other players build completely different engines aiming to mitigate some of MySQL well-known weaknesses, but still support its wire protocol, with the challenge of sacrificing as little compatibility as possible.

In this white paper, we briefly discuss the scale-up vs scale-out dilemma, to then review the different scale-out strategies. We are also going to go over some of the most common MySQL architectures and products with horizontal scaling in mind.

Finally, we will share some guidelines to …

Overview

While working on a MySQL Galera cluster with ProxySQL, I was in the process of testing traffic going to the MySQL nodes by using the @@hostname command to ensure which MySQL host behind the proxy the query ran on. This was important as my client is using query rules to route traffic according to the rule to either the master or the slave.  But to my surprise, I didn’t always get the result that I was expecting.  This is where ProxySQL multiplexing comes into play.

Scenario

In my scenario, I was on a test server connecting to ProxySQL which was then routing my queries to the MySQL Galera nodes.  I would connect into ProxySQL using the MySQL client.

Important note: When testing query routing with ProxySQL using comments and the MySQL client, you have to use the “-c” command line option in order for the comment to not be stripped away when running queries.  You …

The Debian project announced their 15th release, code name Buster, on July 6th 2019. Debian 10 ships with MariaDB 10.3 and Galera. There is no separate MariaDB Connector C package, but instead MariaDB 10.3 includes MariaDB Connector C 3.0. Like most other popular Linux distributions, Debian prefers MariaDB over the Oracle owned alternative and this […]

The post Debian 10 released with MariaDB 10.3 appeared first on MariaDB.org.

Do you want to run Galera Cluster in the cloud? Why not learn to setup a 3-node Galera Cluster using Amazon Web Services (AWS) Elastic Compute Cloud (EC2), and run it yourself (3-node because this is the minimum preferred size; you can have a 5, 7, or 9 node cluster too — not in the demo though!). In this webinar, we will cover the steps to do this, with a demonstration of how easy it is for you to do. We will also cover how you may want to load balance traffic to your Galera Cluster using a proxy like ProxySQL.

In addition, we will cover why you may want to run a 3-node (or more) Galera Cluster (multi-master synchronous clusters) instead of (or in addition to) using Amazon Relational Database Service (RDS) MySQL, which has the ability to have asynchronous replication (Read Replicas), and High Availability provided by DRBD (Multi-AZ). We will also cover where Galera Cluster differs from Amazon Aurora RDS for MySQL.

Join us and …