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MySQL Group Replication: Videocast #1

Hi !

I’m starting a small series of videocast related to MySQL Group Replication.

As I blogged earlier this year about Single-Primary or Multi-Primary Group Replication cluster, one of the limitation of using a cluster in Multi-Primary mode is the risk linked to concurrent DDLs (as ALTER STATEMENTS).

In Group Replication, DDLs are not isolating the full cluster and write operations are not blocked. But this may lead to problems if you change the same table on two different nodes at the same time for example. This is the topic of today’s videocast:

MySQL Group Replication, Single-Primary or Multi-Primary, how to make the right decision ?

Today’s blog post is related again to MySQL Group Replication.

By default MySQL Group Replication runs in Single-Primary mode. And it’s the best option and the option you should use.

But sometimes it might happen that in very specific cases you would like to run you MGR Cluster in Multi-Primary mode: writing simultaneously on all the nodes member of the Group.

It’s of course feasible but you need to make some extra verification as not all workload are compatible with this behavior of the cluster.


The requirements are the same as those for using MGR in Single-Primary mode:

  • InnoDB Storage Engine
  • Primary Keys
  • IPv4 Network
  • Binary Log Active
  • Slave Updates Logged
  • Binary …
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MySQL Group Replication and table design

Today’s article is about the first two restrictions in the requirements page of the manual:

  • InnoDB Storage Engine: data must be stored in the InnoDB transactional storage engine.
  • Primary Keys: every table that is to be replicated by the group must have an explicit primary key defined.

So the first requirement is easy to check by a simple query that list all the non InnoDB tables:

SELECT table_schema, table_name, engine, table_rows, 
       (index_length+data_length)/1024/1024 AS sizeMB 
FROM information_schema.tables 
WHERE engine != 'innodb' 
  AND table_schema NOT IN 
    ('information_schema', 'mysql', 'performance_schema');

The second one is a bit more tricky. Let me show you first how Group Replication behaves:

Case 1: no keys

Let’s create a table with no …

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How to migrate from Galera Cluster to MySQL Group Replication

In this article, I will show you how it’s possible to perform an online migration from a 3 members Galera cluster setup (in this case I’m using PXC 5.7.14) to a 3 members MySQL Group Replication cluster setup (MySQL Community 5.7.17).

Don’t forget that before adopting Group Replication as database backend, you should validate that your application do match GR requirements and limitations. When this is validated, you can start !

So first, let’s have a look at the current situation:


We have an application (sysbench 0.5), reading and writing to a Galera Cluster ( …

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2-Phase Commit in NDBCluster

This is a description of the simplest case of 2-phase commit (2PC) in NDBCluster: one transaction, containing a single insert, update or delete operation on a single row. The PREPARE phase of the 2PC is initiated by the API node (which is a mysqld or a NoSQL client) sending a TCKEYREQ to the Transaction Coordinator of a data node.…

MySQL datamasking using ProxySQL

Percona Live Amsterdam is just finished… there was an entire room full day about MySQL 8.0 which is wonderful but there was also another product that everybody was talking about: ProxySQL (great job René).

Ronald Bradford and the MySQL engineering team were discussing about what tool was missing in the MySQL ecosystem and Mark Leith highlighted that a datamasking utility was really missing.

Having used already ProxySQL for Group Replication and other tests, I knew that it would be possible to use it also for this purpose. After a very short discussion and a nightly chat with …

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Order from Chaos: Member Coordination in Group Replication

We are very excited about the next release of MySQL Group Replication 0.9.0 in MySQL 5.7.15 and the great work that has been done to improve its stability. Release after release, MySQL Group Replication becomes more stable and more user-friendly and has reached a maturity level that made us declare 0.9.0 a release candidate.…

MySQL team: make it easy to give you feedback!

There was a bold announcement during the MySQL Keynote at Oracle Open World. A new product that will mix up with the existing GA server, called MySQL InnoDB Cluster. This is an evolution of MySQL group replication, which has been in the labs for long time, and the MySQL shell, which was introduced as a side feature last April. The boldness I mentioned before is on account of wanting to add to a GA server something that was defined as release candidate despite never having been out of the labs. The product is interesting as it promises to be a quick and painless cluster deployment, with built-in high availability and scalability.

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Slides of yesterday’s presentations in Paris

Yesterday I was in Paris to attend a OpenTech Meetup related to MySQL.

You can find below the two presentations I gave (Warning: in French).

Haute disponibilité my sql avec group réplication from Frédéric Descamps

MySQL 5.7 & JSON – Nouvelles opportunités pour les dévelopeurs from Frédéric Descamps

The audience was very interested and I got …

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HA with MySQL Group Replication and ProxySQL

After having played with MySQL Group Replication and HAProxy, it’s time to show you how easy it’s to setup MySQL HA with ProxySQL.

ProxySQL is a high performance open source proxy for MySQL. It has many features that invite you to discover on and on github.

If you remember, I wrote in my last post that it is recommended to use Group Replication with only one WRITER group member. As it is the preferred architecture, I will show you how to achieve this using ProxySQL. With ProxySQL, you don’t need to have two different interfaces to split reads and writes.

In fact, when you use ProxySQL, you have a much larger amount of options to route your queries. In production, the smart DBA, will identify …

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