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Displaying posts with tag: Percona Server for MySQL (reset)
Danger of Changing Default of log_error_verbosity on MySQL/Percona Server for MySQL 5.7

Changing the default value (3) of log_error_verbosity in MySQL/Percona Server for MySQL 5.7 can have a hidden unintended effect! What does log_error_verbosity do exactly? As per the documentation:

The log_error_verbosity system variable specifies the verbosity for handling events intended for the error log.

Basically a value of 1 logs only [Errors]; 2 is 1)+[Warnings]; and 3 is 2)+[Notes].

For example, one might be tempted to change the default of log_error_verbosity since the error.log might be bloated with thousands (or millions) of lines with [Notes], such as:

2020-10-08T17:02:56.736179Z 3 [Note] Access denied for user 'root'@'localhost' (using password: NO)
2020-10-08T17:04:48.149038Z 4 [Note] Aborted connection 4 to db: 'unconnected' user: 'root' host: 'localhost' (Got timeout reading communication packets)

(P.S. you can read more about those Notes on this other Percona blog posts):

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How to Upgrade to MySQL 8.0 – Free Course at Percona University Online

MySQL 8.0 General Availability release was launched in April 2018, and since then there have been ten versions of MySQL 8 and Percona Server for MySQL released. The MySQL Community expressed a high opinion of the MySQL 8.0 advantages, so a lot of databases have been successfully upgraded to the new version. But many of them still need to be up to date.

Percona has prepared a free course “How to Upgrade to MySQL 8.0” that helps you with this task.

It is a series of useful videos for 3-4 minutes. At the end of the course, you can pass the QUIZ and get a certificate. 

Follow the link to take the course:  https://classroom.google.com/c/MTM2MDIyNDIzMDQy?cjc=zjsst4l

You can also join the course manually. Just open Google Classroom and click “Join class” and enter the code of the class “zjsst4l”. …

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Aligning Percona XtraBackup Versions with Percona Server for MySQL

We are excited to let you know about two upcoming changes to Percona XtraBackup which will align Percona XtraBackup Versions with Percona Server for MySQL.  These changes are to bring Percona XtraBackup release naming line with Percona Server and MySQL and ensure Percona XtraBackup executes complete backups.

The first is a change to the naming structure of releases.  This change is something we believe will help when working with Percona products and is designed to position Percona XtraBackup to be in sync with the current release naming strategy of Percona Server for MySQL and Percona XtraDB Cluster.

The current naming structure of …

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Deadlock Troubleshooting in Percona Server for MySQL 5.7

Disclaimer: the following script only works for Percona Server for MySQL 5.7, and relies on enabling performance schema (PS) instrumentation which can add overhead on high concurrent systems, and is not intended for continuous production usage as it’s a POC (proof of concept).

Introduction

In Percona Support, we frequently receive tickets related to deadlocks and even though the deadlock concept is simple, troubleshooting might not be in all cases. 

As explained in How to Deal with MySQL Deadlocks, a deadlock occurs when two or more transactions mutually hold and request for locks, creating a cycle of dependencies. MySQL will detect deadlocks and kill one of the transactions (making it rollback), and the deadlock will be printed in SEIS (show engine innodb status). Limitations of using this approach …

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How Can ScaleFlux Handle MySQL Workload?

Recently I had the opportunity to test a storage device from ScaleFlux called CSD 2000. In this blog post, I will share the results of using it to run MySQL in comparison with an Intel device that had a similar capacity.

First of all, why do we need another storage device? Why is ScaleFlux any different?

The answer is simple; it gives us built-in compression and atomic writes. For many workloads, but especially for database-type workloads, these are very important features.

Because of built-in compression, we can store more data on the ScaleFlux device than on a similar device with the same capacity.

Because of atomic writes, we can disable InnoDB Double Write buffer which means less writes/fsync on the disk layer. This should give us a performance advantage against non-atomic drives.

I ran many different tests on different data sizes, with different …

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Percona Server for MySQL Highlights – Extended Slow Query Logging

Last year, I made the first post in a small series, which aimed to highlight unique features of Percona Server for MySQL, by discussing binlog_space_limit option.

Today, I am going to discuss another important type of log available in MySQL that is enhanced in Percona Server for MySQL – the slow query log. The reason why I am doing this is that although this extension has existed since the very early times of versions 5.1 (over 10 years ago!), many people are still unaware of it, which I see from time to time when working with Support customers.

Default Slow Log Inadequacy

How many times have you been wondering why, whilst reviewing slow query logs, the very same query occasionally runs way slower than usual? There may be many reasons for that, but the standard slow …

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Unexpected slow ALTER TABLE in MySQL 5.7

Usually one would expect that ALTER TABLE with ALGORITHM=COPY will be slower than the default ALGORITHM=INPLACE. In this blog post we describe the case when this is not so.

One of the reasons for such behavior is the lesser known limitation of ALTER TABLE (with default ALGORITHM=INPLACE) that avoids REDO operations. As a result, all dirty pages of the altered table/tablespace have to be flushed before the ALTER TABLE completion.

Some history

A long time ago, all “ALTER TABLE” (DDLs) operations in MySQL were implemented by creating a new table with the new structure, then copying the content of the original table to the new table, and finally renaming the table. During this operation the table was locked to prevent data inconsistency.

Then, for InnoDB tables, the new algorithms were introduced, which do not involve the full table copy and some operations do not apply the table level lock – first the online …

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Need to Connect to a Local MySQL Server? Use Unix Domain Socket!

When connecting to a local MySQL instance, you have two commonly used methods: use TCP/IP protocol to connect to local address –  “localhost” or 127.0.0.1  – or use Unix Domain Socket.

If you have a choice (if your application supports both methods), use Unix Domain Socket as this is both more secure and more efficient.

How much more efficient, though?  I have not looked at this topic in years, so let’s see how a modern MySQL version does on relatively modern hardware and modern Linux.

Benchmarking  TCP/IP Connection vs Unix Domain Socket for MySQL

I’m testing Percona Server for MySQL 8.0.19 running on Ubuntu 18.04 on a Dual Socket 28 Core/56 Threads Server.  (Though I have validated results on 4 …

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Group Replication in Percona Server for MySQL

Percona Server for MySQL 8.0.18 ships all functionality to run Group Replication and InnoDB Cluster setups, so I decided to evaluate how it works and how it compares with Percona XtraDB Cluster in some situations.

For this I planned to use three bare metal nodes, SSD drives, and a 10Gb network available for in-between nodes communication, but later I also added tests on three bare metal nodes with NVMe drives and 2x10Gb network cards.

To simplify deployment, I created simple ansible scripts.

Load Data

The first initial logical step is to load data into an empty cluster, so let’s do this with our sysbench-tpcc …

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Disk of Yesteryear Compared to Today’s SSD Drives

In my last blog post I showed you how to get the entire Percona “Stack” up and running on a Raspberry Pi. This time around, I would like to show the impact on performance between using an SSD hard disk and a standard hard disk.

Disk performance is a key factor in Percona Server for MySQL (or any RDB platform) performance on a Raspberry Pi 4.

Test set up

Each test below was run three times per Hard Disk and I took the best of the three for comparison.

Hardware

  • Raspberry Pi 4+ with 4GB ram.
  • Disk 1: USB3 Western Digital My Passport Ultra, 1TB
  • Disk 2: USB3 KEXIN 240GB Portable External SSD Drive

Hardware stayed consistent …

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