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MySQL Group Replication, the perfect HA database backend for web hosting

Many web hosting provider are looking for HA solution for the database backend they deliver to their customers.

Galera never became the perfect choice for these environment due to 2 factors:

  1. no DBA really manage the databases
  2. Galera runs database changes in Total Order Isolation

What does that really mean ? In fact, when you are a website hosting provider, you host the website (apache, nginx) on vhosts and you share a database server in which every customer has access to their own schema for their website.

Most of the time, those websites are CMS like Drupal, WordPress or Joomla (and certainly many others sharing the same …

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MySQL group replication: installation with Docker

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 …

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Setup ProxySQL as High Available (and not a SPOF)

During the last few months we had a lot of opportunities to present and discuss about a very powerful tool that will become more and more used in the architectures supporting MySQL, ProxySQL.

ProxySQL is becoming every day more flexible, solid, performant and used (http://www.proxysql.com/ and recent http://www.proxysql.com/compare).

 

This is it, the tool is a winner in comparing it with similar ones, and we all need to have a clear(er) idea on how integrate it in our architectures in order to achieve the best results.

 

The first to keep in mind is that ProxySQL is not natively supporting any high availability solution, in short we can setup a cluster of MySQL(s) and achieve 4 or even 5 nines of HA, but if we include ProxySQL, as it is, and as single …

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Solving MySQL Replication Lag with LOGICAL_CLOCK and Calibrated Delay

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.

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Oracle MySQL and the funny replication breakage of Friday, January 13

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

PHP and MySQL Basics III -- Resulting Results

In the first two blogs entries on this series we set up a connection to MySQL and sent off a query. Now we need to get the data back from the database and into the application.

An Embarrassment of RichesPHP has many options for what we want to do. But for the best place to start with was checking that rows were actually returned from a query. Below the results from a query are returned to a variable named $result. We can find out how many rows were returned from the server by examining $result->num_rows.

if (!$result = $mysqli->query($sql)) {

// Again, do not do this on a public site, but we'll show you how
// to get the error information
echo "Error: Our query failed to execute and here is why: \n";
echo "Query: " . $sql . "\n";
echo "Errno: " . $mysqli->errno . "\n";
echo "Error: " . $mysqli->error . "\n";
exit;
}

// succeeded, but …
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Funny replication breakage of Friday, January 13

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

The Impact of Swapping on MySQL Performance

In this blog, I’ll look at the impact of swapping on MySQL performance. 

It’s common sense that when you’re running MySQL (or really any other DBMS) you don’t want to see any I/O in your swap space. Scaling the cache size (using

innodb_buffer_pool_size

 in MySQL’s case) is standard practice to make sure there is enough free memory so swapping isn’t needed.   

But what if you make some mistake or miscalculation, and swapping happens? How much does it really impact performance? This is exactly what I set out to investigate.

My test system has the following:

  • 32GB of physical memory
  • OS (and swap space) on a (pretty old) Intel 520 SSD device
  • Database stored on Intel 750 NVMe storage

To simulate a worst case scenario, I’m using Uniform Sysbench Workload:

sysbench …
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Sushi = Beer ?! An introduction of UTF8 support in MySQL 8.0

In MySQL 8.0 our plan is to drastically improve support for utf8. While utf8 support itself dates back to MySQL 4.1, there exist some limitations. The “sushi = beer” problem in the title refers to Bug #76553. Sushi and beer don’t even go well together, at least not to my taste:-) I will use this bug as an example to explain issues with utf8 collations in the past and our plans for utf8 support going forward.…

Online schema change with gh-ost - throttling and changing configuration at runtime

Related resources  Schema Changes for MySQL Replication & Galera Cluster  Database Cluster Management - Manual vs Automation via ClusterControl  Migrating to MySQL 5.7 - The Database Upgrade Guide

In previous posts, we gave an overview of gh-ost and showed you how to test your schema changes before executing …

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