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Displaying posts with tag: Insight for DBAs (reset)
WAN Synchronous Clusters: Dealing with Latency Using Concurrency

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 …

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MySQL Sharding Models for SaaS Applications

In this blog post, I’ll discuss MySQL sharding models, and how they apply to SaaS application environments.

MySQL is one of the most popular database technologies used to build many modern SaaS applications, ranging from simple productivity tools to business-critical applications for the financial and healthcare industries.

Pretty much any large scale SaaS application powered by MySQL uses sharding to scale. In this blog post, we will discuss sharding choices as they apply to these kinds of applications.

In MySQL, unlike in some more modern technologies such as MongoDB, there is no standard sharding implementation that the vast majority of applications …

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When MySQL Lies: Wrong seconds_behind_master with slave_parallel_workers > 0

In today’s blog, I will show an issue with seconds_behind_master that one of our clients faced when running slave_parallel_works > 0. We found out that the reported seconds_behind_master from SHOW SLAVE STATUS was lying. To be more specific, I’m talking about bugs #84415 and #1654091.

The Issue

MySQL will not report the correct slave lag if you have slave_parallel_workers> 0. Let’s show it in practice.

I’ll use MySQL Sandbox to speed up one master and two slaves on MySQL version …

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Ad-hoc Data Visualization and Machine Learning with mysqlshell

In this blog post, I am going to show how we can use mysqlshell to run ad-hoc data visualizations and use machine learning to predict new outcomes from the data.

Some time ago Oracle released MySQL Shell, a command line client to connect to MySQL using the X protocol. It allows us to use Python or JavaScript scripting capabilities. This unties us from the limitations of SQL, and the possibilities are infinite. It means that MySQL can not only read data from the tables, but also learn from it and predict new values from features never seen before.

Some disclaimers:

  • This is not a post about to how to install mysqlshell or enable the X plugin. It should be already installed. Follow the first link if instructions are needed.
  • The idea is to show some of the things that can be done from the shell. Don’t expect the …
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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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Reinstall MySQL and Preserve All MySQL Grants and Users

In this blog post, we’ll look at how to preserve all MySQL grants and users after reinstalling MySQL.

Every so often, I need to reinstall a MySQL version from scratch and preserve all the user accounts and their permissions (or move the same users and privileges to another server).

As of MySQL 5.7, MySQL does not make this easy! MySQL SHOW GRANTS only shows permissions for one user, and the method suggested on StackExchange – dumping tables containing grants information directly – is not robust (as Rick James mentions in the comments). It also doesn’t work between different MySQL versions.

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How to Move a MySQL Partition from One Table to Another

In this blog post we’ll look at how to move a MySQL partition from one table to another, for MySQL versions before 5.7.

Up to version 5.7, MySQL had a limitation that made it impossible to directly exchange partitions between partitioned tables. Now and then, we get questions about how to import an .ibd for use as a partition in a table, as well as how to exchange partitions with another partitioned table. Below is step-by-step instructions on how to move a partition from one table to another.

In this example, one of our customers had two tables with the following structures:

CREATE TABLE live_tbl (
some_id bigint(20) NOT NULL DEFAULT '0',
summary_date date NOT NULL,
PRIMARY KEY (some_id,summary_date)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
/*!50500 PARTITION BY RANGE …
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MySQL 8.0.1: The Next Development Milestone

This post discusses the next MySQL development milestone: MySQL 8.0.1.

From the outset, MySQL 8.0 has received plenty of attention. Both this blog (see the MySQL 8.0 search) and other sites around the Internet have covered it. Early reviews seem positive (including my own MySQL 8.0 early bugs review). There is plenty of excitement about the new features.

As for early feedback on MySQL 8.0, Peter Zaitsev (Percona CEO) listed a set of recommendations for benchmarking MySQL 8.0. I hope these get reviewed and implemented. …

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Archiving MySQL and MongoDB Data

This post discusses archiving MySQL and MongoDB data, and determining what, when and how to archive data.

Many people store infrequently used data. This data is taking up storage space and might make your database slower than it could be. Archiving data can be a huge benefit, both regarding the performance impact and storage savings.

Why archive?

One of the reasons for archiving data is freeing up space on your database volumes. You can store archived data on slower, less expensive storage devices, and current data on the faster database drives. Archiving old data makes backups and restores run faster since they need to process less data. Last, but by no means least, archiving data has the benefit of making your queries perform more efficiently since they do not need to process through old …

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Enabling and Disabling Jemalloc on Percona Server

This post discusses enabling and disabling jemalloc on Percona Server for MySQL.

The benefits of jemalloc versus glibc for use with MySQL have been widely discussed. With jemalloc (along with Transparent Huge Pages disabled) you have less memory fragmentation, and thus more efficient resource management of the available server memory.

For standard installations of Percona Server 5.6+ (releases starting with 5.6.19-67.0), the only thing needed to …

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Showing entries 31 to 40 of 483
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