Recently, my friend Marco Tusa(MySQL Daddy or the Grinch) wrote his first impression on MySQL Group Replication (part of InnoDB Cluster). And his conclusion was not that positive. But when I analyze his setup, I understand that his assumptions were not so right.

Let's try to explain what were the issues and why his test wasn't correct.

Before commenting Marco's tests, I would like to clarify the flow-control implementation in Group Replication:

We designed the flow-control feature in Group Replication as a safety measure for delaying writer nodes when they consistently exceed the write capacity of the Group, so that a large backlog would not make it hard to switch over from a member to another.

Flow-control is …

When using MySQL Group Replication, it’s possible that some members are lagging behind the group. Due to load, hardware limitation, etc… This lag can become problematic to keep good certification behavior regarding performance and keep the possible certification failure as low as possible. Bigger is the applying queue bigger is the risk to have conflicts with those not yet applied transactions (this is problematic on Multi-Primary Groups).

Galera users are already familiar with such concept. MySQL Group Replication’s implementation is different 2 main aspects:

• the Group is never totally stalled
• the node having issues doesn’t send flow control messages to the rest of the group asking for slowing down

In fact, every member of the Group send some statistics about its queues (applier queue and certification queue) to the other members. Then every node decide to slow down or not if they …

The Debian project has today announced their 9th release, code named “Stretch”. This is a big milestone for MariaDB, because the release team decided to ship and support only one MySQL variant in this release, and MariaDB was chosen over MySQL. This is prominently mentioned in the press release about Debian 9 and more information […]

The post Debian 9 released with MariaDB as the only MySQL variant appeared first on MariaDB.org.

In a perfect world, one would upgrade databases one version at a time and not let them get too old.  But our databases are where the “crown jewels” are.  They must stay up 24×7.  When performance is acceptable, it’s acceptable, and sometimes old versions stay around too long.  We don’t live in a perfect world.  This idea applies to so many things.  There’s almost never a perfect data model.  There is always some type of resource constraint be it storage, memory, CPU, IOPS, or just plain dollars.

I will bring this concept of not living in a perfect world into a discussion about upgrades.

Ideally there would be…

• …time to do two upgrades.  One upgrade to 5.6, the other to 5.7.   This is the way sane, normal people upgrade.
• …a lot of extra hardware.  It sure would be nice to maybe combine a maintenance like this with a hardware refresh so that …

We saw yesterday that the new MySQL Shell was out and how we could create a MySQL InnoDB Cluster manually using the Shell.

Today, I would like to show you how easy it is to create recipes to automate all the process. I have created a Puppet module that can be used as Proof-of-concept (You might need more features to use it in production, feel free to fork it).

The module can be found on this github repo.

When using Puppet, I really like to put all configuration in hiera.

Environment

We have 3 GNU/Linux servers: mysql1, mysql2 and mysql3.

We won’t install anything related to MySQL manually, everything will be handled by Puppet.

Nodes definition …

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.

Requirements

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 …

Today in our series of articles related to MySQL Group Replication’s limitations, let’s have a quick look at Savepoints.

The manual is clear about this: Transaction savepoints are not supported.

The first thing to check then is if the application that will use our MySQL Group Replication Cluster is currently using savepoints.

We have two ways to find this, the first is using STATUS variables:

mysql> show global status like '%save%';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Com_release_savepoint      | 2     |
| Com_rollback_to_savepoint  | 0     |
| Com_savepoint              | 4     |
| Handler_savepoint          | 0     |
| Handler_savepoint_rollback | 0     |
+----------------------------+-------+

…

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 …

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 ( …

It’s a wonderful news, we have released MySQL 5.7.17 with Group Replication Plugin (GA quality).

From the definition, Group Replication is a multi-master update everywhere replication plugin for MySQL with built-in conflict detection and resolution, automatic distributed recovery, and group membership.

So we can indeed compare this solution with Galera from Codership which is a Replication Plugin implementing the WSREP API. WSREP, Write Set Replication,  extends the replication API to provide all the information and hooks required for true multi-master, “virtually synchronous” replication.

With Group Replication, MySQL implemented all this information …