The latest from the MySQL community

Starting with Percona XtraDB Cluster (PXC) 8.0, replication traffic encryption is enabled by default. That said, it’s common to find clusters running without TLS that suddenly need it: a new compliance requirement, an audit finding, a network segment that is no longer considered trusted.

PXC has a variable for exactly that case, pxc-encrypt-cluster-traffic, which handles SSL encryption for inter-node traffic, including State Snapshot Transfer (SST), Incremental State Transfer (IST), and the group communication the nodes use for replication.

The variable is not dynamic, and turning it on normally costs a full cluster restart since the node that encrypts traffic listens on ssl:// while its peers are still on tcp://. If a node joins the cluster with TLS enabled while remaining nodes don’t, the restarting node fails to reach out to the other peers with the following error:

2026-09-02T02:16:02.359992Z 0 [Note] [MY-000000] …

The common practice is to size the Galera Cache based on write volume measured during peak load, but often it is more of a guesswork. The writeset cache capacity planning is crucial to shorten the maintenance time and avoid long state transfers while the cluster runs with reduced compute power. Now, if you could understand what’s exactly inside the cache, wouldn’t the planning be more aware as compared to only calculating the best size based on wsrep_received/replicated_bytes variables?

Similarly, while dealing with various incidents occurring in Percona XtraDB Cluster or MariaDB Galera Cluster environments, how many times did you stumble upon the fact that the GCache file (galera.cache) is a black box and you can’t inspect it in a meaningful way? 

In some scenarios, having the opportunity to see what exactly ended up in the cache file(s) could help us understand the write workload impact or what happened …

At Percona, we’ve always been dedicated to providing robust, open source high availability solutions that meet our users’ evolving needs. Percona XtraDB Cluster (PXC) stands as a testament to this commitment, offering a highly available and scalable solution for your MySQL and Percona Server for MySQL deployments. We understand that database high availability is critical […]

Any Galera documentation about limitations will state that tables must have primary keys. They state that DELETEs are unsupported and other DMLs could have unwanted side-effects such as inconsistent ordering: rows can appear in different order on different nodes in your cluster.If you are not actively relying on row orders, this could seem acceptable. Deletes […]

Recently, I was working on a very unfortunate case that revolved around diverging clusters, data loss, missing important log errors, and forcing commands on Percona XtraDB Cluster (PXC). Even though PXC tries its best to explain what happens in the error log, I can vouch that it can be missed or overlooked when you do not know what to expect.

This blog post is a warning tale, an invitation to try yourself and break stuff (not in production, right?).

TLDR:
Do you know right away what happened when seeing this log?

2023-06-22T08:23:29.003334Z 0 [ERROR] [MY-000000] [Galera] gcs/src/gcs_group.cpp:group_post_state_exchange():433: Reversing history: 171 -> 44, this member has applied 127 more events than the primary component.Data loss is possible. Must abort.

Demonstration

Using the …

Percona XtraDB Cluster 8.0.25 (PXC) has introduced a new option to perform online schema modifications: NBO (Non-Blocking Operation).

When using PXC, the cluster relies on the wsrep_OSU_method parameter to define the Online Schema Upgrade (OSU) method the node uses to replicate DDL statements. 

Until now, we normally have three options:

• Use Total Isolation Order (TOI, the default)
• Use Rolling Schema Upgrade (RSU)
• Use Percona’s online schema change tool (TOI + PTOSC)

Each method has some positive and negative aspects. TOI will lock the whole …

MySQL InnoDB Cluster is the official High Availability solution for and from MySQL.

MySQL InnoDB Cluster is composed by MySQL Server, MySQL Group Replication, MySQL Router and MySQL Shell.

Before InnoDB Cluster there was no standard solution for MySQL Availability and many custom solutions were used (some better than the others). But there was a good solution using some similar principles of MySQL Group Replication: Galera.

Now that MySQL InnoDB Cluster is mature and easier to orchestrate than galera, I receive a lot of requests on how to migrate from Galera (or Percona XtraDB Cluster) to MySQL InnoDB Cluster.

I already wrote some time ago an article on this process: how to migrate from Galera to MySQL Group Replication.

In this article we will see how we can migrate from Percona XtraDB …

Codership is pleased to announce a new Generally Available (GA) release of the multi-master Galera Cluster for MySQL 5.6, 5.7 and 8.0, consisting of MySQL-wsrep 5.6.51 (release notes, download), 5.7.33 (release notes, download) and 8.0.23 (release notes, download) with Galera replication library 3.33 ( …

Galera replication technology, a key component of Percona XtraDB Cluster, suffered from a remote code execution vulnerability. Percona has been working with the vendor since early September on this issue and has made releases available to address the problem.

Applicability

A malicious party with access to the WSREP service port (4567/TCP) as well as prerequisite knowledge of the configuration of the Galera cluster name is required in order to exploit this vulnerability, which leads to remote code execution via the WSREP protocol. 

Fixes are available in Percona XtraDB Cluster versions:

>= 8.0.20-11.2

>= …

Schema changes are the big challenges in Galera replication. So, it is recommended to understand the schema changes operation for everyone who uses the Percona XtraDB Cluster (PXB)/Galera clusters. In this blog, I am going to explain the operation and impact of the various schema changes methods used in the PXB/Galera cluster.

• Schema changes with “wsrep_OSU_method = TOI”
• Schema changes with “wsrep_OSU_method = RSU”
• Schema changes with “ONLINE ALGORITHMS”
• Schema changes with “pt-osc”
• Schema changes with “gh-ost”

For testing:

• I have configured the 3-node Percona Xtradb Cluster (8.0.19).
• Executing read/write load using the sysbench.

mysql> select @@wsrep_cluster_address\G
*************************** 1. row …