It is time to talk again about Flow control and group replication. This time with a special eye on the use of Group Replication in the Kubernetes context. In this article we will dig a bit on how it works and what are the various side effects. 

The problem

Recently I was refining the calculation I use in the MySQL calculator for Operator given I was constantly encountering a very serious problem with the Percona Server Operator.

The problem is that when the deployment was/is serving a high level of traffic, it will, no matter what, end up in getting OMMKill by the K8 system. 

This because the pod was gradually consuming more and more memory, reaching the memory limit set in the CR specification. 

Now let me clarify a few things, to get straight to the facts.

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I’m working on sharing MySQL tips, tricks, and other related tech topics in my MySQL podcast. It’s a bit of a challenge to stay consistent, but I’m pushing through. Finally…

The post MySQL Podcast: InnoDB Cluster Group Replication first appeared on Change Is Inevitable.

It may be surprising when a new InnoDB Cluster is set up, and despite not being in production yet and completely idle, it manifests a significant amount of writes visible in growing binary logs. This effect became much more spectacular after MySQL version 8.4. In this write-up, I will explain why it happens and how to address […]

MySQL 8.4 has two good options for High Availability clusters: Galera Cluster (and Percona XtraDB Cluster (PXC)) plus MySQL InnoDB Cluster. Both solutions are now mature enough, so what is the deciding factor? Workload characteristics, application compatibility (Galera is virtually synchronous; InnoDB Cluster offers 2 modes – single primary mode, which is one instance being read-write, with the rest being read only, and multi-primary mode, which is closer to what Galera Cluster is) and operational preferences, most likely will decide which one comes out top in 2025, is what we aim to answer at next week’s webinar.

Due to the lack of real-world usage statistics (we can tell you how many Galera Cluster downloads we have, for example, or even customer numbers, but we won’t have anything to compare against), we look at proxy statistics, like …

Group replication is a fault-tolerant/highly available replication topology that ensures if the primary node goes down, one of the other candidates or secondary members takes over so write and read operations can continue without any interruptions. However, there are some scenarios where, due to outages, network partitions, or database crashes, the group membership could be broken, or we end […]

Flow control is not a new term, and we have already heard it a lot of times in Percona XtraDB Cluster/Galera-based environments.  In very simple terms, it means the cluster node can’t keep up with the cluster write pace. The write rate is too high, or the nodes are oversaturated. Flow control helps avoid excessive […]

TL;DR: Make sure to run “SET persist_only disabled_storage_engines=’MyISAM’, persist sql_generate_invisible_primary_key=ON;” on all instances and restart each one in your MySQL InnoDB Cluster.

Ok, what does “safe from naughtiness” mean?:
– Anyone creating tables that aren’t InnoDB, as this doesn’t make sense, after all, it is an “InnoDB” cluster.
– Making sure all tables have a Primary Key (invisible or not).
– Making sure that my (invisible) primary keys are visible to the cluster as it will rightfully complain if they aren’t!

This basically means that once you’ve got it all up and running you won’t run into those horrible situations whereby someone, somewhere, creates a MyISAM table that didn’t have a Primary Key and thus leave you with a broken cluster.

Eg.

MySQL rtnode-01:3306 ssl JS > vlc.status()
{
 "clusterName": "VLC",
 "clusterRole": "PRIMARY", …

Maintaining a production dataset at a manageable size can present a considerable challenge during the administration of a MySQL InnoDB Cluster.

Old Days

Back in the day when we only had one main copy of our data (the source), and one read copy (the replica) that we used to look at current and old data from our main system, we used a special trick to remove data without affecting the replica. The trick was to turn off writes to the binary log for our removal commands in the main system. External tools like pt-archiver were also able to use that trick. To stop bypass writing into the binary log, we used the command: SET SQL_LOG_BIN=0.

This mean that on the main production server (replication source), we were purging the data without writing the delete operation into the binary logs:

Current Days

These …

When working with group replication, MySQL router would be the obvious choice for the connection layer. It is tightly coupled with the rest of the technologies since it is part of the InnoDB cluster stack.The problem is that except for simple workloads, MySQL router’s performance is still not on par with other proxies like Haproxy […]

Many of us, old MySQL DBAs used Seconds_Behind_Source from SHOW REPLICA STATUS to find out the status and correct execution of (asynchronous) replication.

Please pay attention of the new terminology. I’m sure we’ve all used the old terminology.

However, MySQL replication has evolved a lot and the replication team has worked to include a lot of useful information about all the replication flavors available with MySQL.

For example, we’ve added parallel replication, group replication, … all that information is missing from the the good old SHOW REPLICA STATUS result.

There much better ways to monitoring and observing the replication process(es) using Performance_Schema.

Currently in Performance_Schema, there are 15 tables relating to replication instrumentation:

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