In this blog, we’ll discuss how to use concurrency to help with WAN latency when using synchronous clusters.

WAN Latency Problem

Our customers often ask us for help or advice with WAN clustering problems. Historically, the usual solution for MySQL WAN deployments is having the primary site in one data center, and stand-by backup site in another data center (replicating from the primary asynchronously). These days, however, there is a huge desire to employ available synchronous replication solutions for MySQL. These solutions include things like Galera (i.e., Percona XtraDB Cluster) or the recently released MySQL Group Replication. This trend is attributable to the fact that these solutions are less problematic and provide more automatic fail over and fail back procedures. But it’s also because businesses want to write in both data centers simultaneously.

Unfortunately, WAN link reliability and latency makes …

I will be heading to Brussels on Friday for FOSDEM.

On Friday, February 3rd, I will attend the Pre-FOSDEM MySQL Day where I will give two talks:

How Booking.com avoids and deals with replication lag (at 12:05), Monitoring Booking.com without looking at MySQL (at 15:30).

(A summary of those talks can be found in Le Fred's blog.)

Then, on Saturday, February 4th, I have a talk in the MySQL

In my previous post, we saw the usage of MySQL Group Replication (MGR) in single-primary mode. We know that Oracle does not recommends using MGR in multi-primary mode, but there is so much in the documentation and in presentations about MGR behavior in multi-primary, that I feel I should really give it a try, and especially compare this technology with the already existing multiple master solution introduced in 5.7: multi-source replication.

Installation

To this extent, I will set up two clusters using MySQL-Sandbox. The instructions for MGR in …

Join Percona’s Chief Evangelist Colin Charles on Wednesday, January 18, 2017, at 7:00 am (PST) / 10:00 am (EST) (UTC-8) as he presents “Lessons from Database Failures.”

MySQL failures at scale can teach a great deal. MySQL failures can lead to a discussion about such topics as high availability (HA), geographical redundancy and automatic failover. In this webinar, Colin will present case study material (how automatic failover caused Github to go offline, why Facebook uses assisted failover rather than fully automated failover, and other scenarios) to look at how the MySQL world is making things better. One way, for example, is using …

Overview

MySQL Group Replication was released as GA with MySQL 5.7.17. It is essentially a plugin that, when enabled, allows users to set replication with this new way.

There has been some confusion about the stability and usability of this release. Until recently, MySQL Group Replication (MGR) was only available in the Labs, which traditionally denotes a preview or an use-at-your-own-risk feature. Several months ago we saw the release of Group Replication as a Docker image, which allowed users to deploy a peer-to-peer cluster (every node is a master.) However, about one month after such release, word came from Oracle discouraging this setup, and inviting users to use Group Replicator in …

Last week VividCortex's Preetam Jinka published a post on his personal blog examining how our engineering team had overcome a problem with MySQL replication by using a new parallelization policy introduced in MySQL 5.7: LOGICAL_CLOCK.

Image Credit

The solution we developed—which achieves faster replication via group commit and a carefully calibrated delay—can offer huge replication improvements, but its implementation isn't immediately obvious or intuitive. We thought it worthwhile to provide a fuller description of how we arrived at the solution Preetam outlined.

In my previous post, I talked about a funny replication breakage that I experienced with MariaDB.  So what about different versions of MySQL... > SELECT version(); +------------+ | version() | +------------+ | 5.6.35-log | +------------+ 1 row in set (0.00 sec) > SELECT * FROM test_jfg; +----+--------+-------------+ | id | status

A funny replication breakage kept me at the office longer than expected today (Friday 13 is not kind with me).

So question of the day: can you guess what the below UPDATE statement does (or what is wrong with it)?

> CREATE TABLE test_jfg ( id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, status ENUM('a','b') NOT NULL DEFAULT 'a', txt TEXT); Query OK, 0

OK, let me start with saying that a table without a primary key shouldn't be something that a DBA should ever stumble into.  Sure, InnoDB will secretly add one for us without telling - but that's not something we can use at application or administration level, it's just to make the engine happy.

So let's suppose you find some tables that lack a primary key, of course you need to do something about it, right?  Now, put Galera Cluster in the mix - Galera does not support tables without a primary key and will, secretly again, make that table inconsistent at cluster level.

You need to fix the damn table(s)!! And this is where the fun begins...  as you can't afford downtime for the operation so you need to resort to an online schema change of some type.

Galera cluster is …

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