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Displaying posts with tag: pxc (reset)
Preventing Stale Reads on Percona XtraDB Cluster by Enforcing Causality Checks on a Per-Query Basis

When we run a SELECT in a replica server and it returns a different result to the one we would have obtained had we queried the source server instead, due to changes in the dataset that have not yet been replicated or synchronized to the replica, we get what is known as a stale read. My colleague Marcelo has blogged about Stale Reads and How to Fix Them before.

The need to avoid stale reads is a constraint that leads people into migrating to Percona XtraDB Cluster (PXC) / Galera Cluster or, more recently, Group Replication. I am focusing on PXC and Galera in this short blog post, which, similar to Group Replication, implements not exactly a synchronous replication model but what is commonly referred to as a …

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Online DDL With Group Replication in MySQL 8.0.27

In April 2021, I wrote an article about Online DDL and Group Replication. At that time we were dealing with MySQL 8.0.23 and also opened a bug report which did not have the right answer to the case presented. 

Anyhow, in that article I have shown how an online DDL was de facto locking the whole cluster for a very long time even when using the consistency level set to EVENTUAL.

This article is to give justice to the work done by the MySQL/Oracle engineers to correct that annoying inconvenience. 

Before going ahead, let us remember how an Online DDL was propagated in a group replication cluster, and identify the differences with what happens now, all with the consistency level set to EVENTUAL ( …

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Resolving the MySQL Active-Active Replication Dilemma

Multi-writer replication has been a challenge in the MySQL ecosystem for years before truly dedicated solutions were introduced – first Galera (and so Percona XtradDB Cluster (PXC)) replication (around 2011), and then Group Replication (first GA in 2016).

Now, with both multi-writer technologies available, do we still need traditional asynchronous replication, set up in active-active topology? Apparently yes, there are still valid use cases. And you may need it not only when for some reason Galera/PXC or GR are not suitable, but also when you actually use them. Of course, the most typical case is to have a second cluster in a different …

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Yearly Reminder: DDLs That Fail to Propagate May Cause Percona XtraDB Cluster Inconsistencies

Apologies for the silly title, but the issue is a real one, even though it is not a new thing. Schema upgrades are not an ordinary operation in Galera. For the subject at hand, the bottom line is: under the default Total Order Isolation (TOI) method, “the cluster replicates the schema change query as a statement before its execution.” What this means in practice is that a DDL issued in one node is replicated to other nodes in the cluster before it is even executed in the source node, let alone completed successfully.

As a result of this, it may fail in one node and be successful in another, and this without raising loud alerts or stopping nodes to protect against data inconsistency. This is not a bug in itself but rather a compromise of design. With new changes in MySQL and the …

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Infinitely Scalable Storage with High Compression Feature

It is no secret that compute and storage costs are the main drivers of cloud bills. Migration of data from the legacy data center to the cloud looks appealing at first as it significantly reduces capital expense (CapEx) and keeps operational expenses (OpEx) under control. But once you see the bill, the lift and shift project does not look that promising anymore. See Percona’s recent open source survey which shows that many organizations saw an unexpected growth around cloud and data.

Storage growth is an organic process for the expanding business: more customers store more data, and more data needs more backups and disaster recovery storage for low RTO.

Today, the Percona Innovation Team, which is part of the Engineering organization, is proud to announce a new feature – High Compression. With this feature enabled, …

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Smart Update Strategy in Percona Kubernetes Operator for Percona XtraDB Cluster

In Percona Kubernetes Operator for Percona XtraDB Cluster (PXC) versions prior to 1.5.0, there were two methods for upgrading PXC clusters, and both of these use built-in StatefulSet update strategies. The first one is manual (OnDelete update strategy) and the second one is semi-automatic (RollingUpdate strategy). Since the Kubernetes operator is about automating the database management, and there are use cases to always keep the database up to date, a new smart update strategy was implemented.

Smart Update Strategy

The smart update strategy can be used to enable automatic context-aware upgrades of PXC clusters between minor versions. One of the use cases for automatic upgrades is if you want to get security …

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Replication Between Two Percona XtraDB Clusters, GTIDs and Schema Changes

I got this question on the “How to Avoid Pitfalls in Schema Upgrade with Percona XtraDB Cluster (PXC)” webinar and wanted to answer it in a separate post.

Will RSU have an effect on GTID consistency if replication PXC cluster to another cluster?

Answer for this: yes and no.

Galera assigns its own GTID for the operations, replicated to all nodes of the cluster. Such operations include DML (

INSERT/UPDATE/DELETE

 ) on InnoDB tables and DDL commands, executed with default TOI method. You can find more details on how GTIDs work in the Percona XtraDB Cluster in this blog post.

However, DDL commands, executed with RSU method, are …

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Join ProxySQL Tech Talks with Percona on June 4th, 2020!

Long months of the pandemic lockdown have brought to life many great online events enabling the MySQL community to get together and stay informed about the very recent developments and innovations available to MySQL users. It isn’t over yet! Next Thursday, June 4th, Percona & ProxySQL are co-hosting the ProxySQL Tech Talks with Percona virtual meetup covering ProxySQL, MySQL and Percona XtraDB Cluster.

The attendees are invited to participate in the two-hour deep-dive event with plenty of time for questions and answers (we will have two 40-minute sessions + 20 minutes allocated for Q&A). Get prepared, come with your burning questions and true war stories – we’ll have our speakers answer and comment on them! And here come the speakers:

  • René Cannaò, ProxySQL author and CEO of ProxySQL …
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MySQL Group Replication – Partial Network Failure Performance Impact

In this two-part blog series, I wanted to cover some failover scenarios with Group Replication. In part one, I will discuss an interesting behavior and performance degradation I discovered while writing these posts. In part two, I will show several failover scenarios and demonstrate how Group Replication handles each situation.

The test environment is very basic, a three-node Group Replication (mysql1,mysql2,myslq3) on MySQL 8.0.19 with default settings. mysql2 is the Primary node.

In this scenario, I was testing a partial network failure when a node gets separated from the primary, but other nodes still can see it.

You would think mysql3 is going to lose quorum and exit the cluster, but no. Inside the cluster, all the nodes are in constant communication with each other, not just …

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Help Drive the Future of Percona XtraDB Cluster

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

Improvements and New Features in Percona XtraDB Cluster

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

  • Streaming replication to support 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 …
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