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Displaying posts with tag: Insight for Developers (reset)
How Much Memory Does the Process Really Take on Linux?

One of the questions you often will be faced with operating a Linux-based system is managing memory budget. If a program uses more memory than available you may get swapping to happen, oftentimes with a terrible performance impact, or have Out of Memory (OOM) Killer activated, killing process altogether.

Before adjusting memory usage, either by configuration, optimization, or just managing the load, it helps to know how much memory a given program really uses.

If your system runs essentially a single user program (there is always a bunch of system processes) it is easy.  For example, if I run a dedicated MySQL server on a system with 128GB of RAM I can use “used” as a good proxy of what is used and “available” as what can still be used.

root@rocky:/mnt/data2/mysql# free -h …
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Streaming Percona XtraBackup for MySQL to Multiple Destinations

Have you ever had to provision a large number of instances from a single backup? The most common use case is having to move to new hardware, but there are other scenarios as well. This kind of procedure can involve multiple backup/restore operations which can easily become a pain to administer. Let’s look at a potential way to make it easier using Percona Xtrabackup. The Percona XtraBackup tool provides a method of performing fast and reliable backups of your MySQL data while the system is running.

Leveraging Named Pipes

As per the Linux manual page, a FIFO special file (a named pipe) is similar to a pipe except that it is accessed as part of the filesystem. It can be opened by multiple processes for reading or writing.

For this …

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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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MySQL 8.x DDL Rewriter and Query Rewriter Plugins: Implementation and Use Cases

Rewriting a MySQL query for performance is an important process that every DBA should be aware of so they can fix the wrong queries on runtime without code changes on the application end. ProxySQL has great support for rewriting the queries, which Alkin Tezuysal already explored in his excellent blog ProxySQL Query Rewrite Use Case.

So far, MySQL community provides two built-in query rewrite plugins to perform this task. Recently they introduced the plugin “ddl_rewriter”.

  • query rewriter plugin : It has support for INSERT / UPDATE / DELETE / REPLACE statements from MySQL 8.0.12. 
  • ddl_rewritter plugin: It supports the CREATE TABLE statement. Introduced at MySQL 8.0.16.

In this blog, I am going to explain the complete process of the implementation and the …

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Finding a Regression in MySQL Source Code: A Case Study

At the Percona engineering team, we often receive requests to analyze changes in MySQL/Percona Server for MySQL behavior from one version to another, either due to regression or a bug fix (when having to point out to a customer that commit X has fixed their issue and upgrading to a version including that fix will solve their problem).

In this blog post, we will analyze the approach used to fix PS-7019 – Correct query results for LEFT JOIN with GROUP BY.

Each release comes with a lot of changes. For example, the difference between MySQL 8.0.19 to 8.0.20:

git diff mysql-8.0.19..mysql-8.0.20 | wc -l
737454
git diff mysql-8.0.19..mysql-8.0.20 --name-only | wc -l
4495

737K lines in 4495 files have changed from one minor version to another.

git …
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Using SKIP LOCK For Queue Processing in MySQL

A small thing that provides a huge help.

The other day I was writing some code to process a very large amount of items coming from a social media API. My items were ending in a queue in MySQL and then needed to be processed and eventually moved.

The task was not so strange,  but what I have to do is to develop a queue processor.  Now when you need to process a queue you have two types of queue: static and dynamic.

The static comes in a batch of N number of items in a given time interval and is normally easier to process given you have a defined number of items that you can split in chunks and process in parallel.

The dynamic is… well… more challenging. One option is to wait to have a predefined number of items, and then process them as if they were a static queue.

But this approach is not very good, given it is possible that it will delay a lot …

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The Transaction Behavior Impact of innodb_rollback_on_timeout in MySQL

I would say that innodb_rollback_on_timeout is a very important parameter. In this blog, I am going to explain “innodb_rollback_on_timeout” and how it affects the transaction behavior at the MySQL level. I describe two scenarios with practical tests, as it would be helpful to understand this parameter better.

What is innodb_rollback_on_timeout?

The parameter Innodb_rollback_on_timeout will control the behavior of the transaction when a failure occurs with timeout.

  • If –innodb-rollback-on-timeout=OFF ( default ) is specified, InnoDB rollbacks only the last statement on a transaction timeout.
  • If –innodb-rollback-on-timeout=ON is specified, a transaction timeout causes InnoDB to abort and roll back the entire transaction.

Let’s conduct the test with the …

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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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Webinar 2/26: Building a Kubernetes Operator for Percona XtraDB Cluster

This talk covers some of the challenges we sought to address by creating a Kubernetes Operator for Percona XtraDB Cluster, as well as a look into the current state of the Operator, a brief demonstration of its capabilities, and a preview of the roadmap for the remainder of the year. Find out how you can deploy a 3-node PXC cluster in under five minutes and handle providing self-service databases on the cloud in a cloud-vendor agnostic way. You’ll have the opportunity to ask the Product Manager questions and provide feedback on what challenges you’d like us to solve in the Kubernetes landscape.

Please join Percona Product Manager Tyler Duzan on Wednesday, February 26, 2020, at 1 pm EST for his webinar “Building a Kubernetes Operator for Percona XtraDB Cluster”.

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ClickHouse and MySQL – Better Together

It’s been a while since I wrote about ClickHouse, there are a lot of new features that are worth mentioning, and for this, I recommend to follow the Altinity Blog but today I want to look at the improved integration of ClickHouse and MySQL.

There are two features:

  1. Using MySQL protocol and MySQL client to connect to ClickHouse
  2. Use MySQL tables to select and join with ClickHouse tables

Using MySQL Protocol

By enabling MySQL protocol in ClickHouse server, you will allow for the MySQL command line tool or applications that typically connect to MySQL to connect to ClickHouse and execute queries.

With this, keep in mind:

  • It does not automatically allow you to use MySQL SQL syntax, you still need to write queries in ClickHouse-dialect.
  • The same issue with datatypes. ClickHouse uses Int32/Int64 …
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