Here at Pythian we like to pay attention to what brings people to our site, and one of the main queries we’ve been seeing is “How can I allow a remote MySQL database connection?” Since our mission is to help you love your data, we asked Matthias Crauwels, Lead Database Consultant on one of Pythian’s MySQL teams to address this topic. Over to Matthias!

I’m hoping this may be the start of a series of posts where I can share some common MySQL knowledge in a (hopefully) clear and understandable manner. So let’s get started.

Technical requirements

Historically MySQL allows a client to connect in two different ways. You can either use a local socket solution (on a Linux/Unix system this is called a Unix socket, whereas on Windows systems it’s a named pipe) or via a TCP connection to a listening port (by default 3306).

Since the introduction of MySQL 8.0, a third way is also available using a newer …

Editor’s Note: Because our bloggers have lots of useful tips, every now and then we update and bring forward a popular post from the past. Today’s post was originally published on May 23, 2018.

In recent weeks I’ve been focusing on Docker in order to get a much better understanding of the containerized world that is materializing in front of us. Containers aren’t just for stateless applications anymore and we’re seeing more cases where MySQL and other databases are being launched in a containerized fashion, so it’s important to know how to configure your MySQL container!

In docker hub, you will see an option for this by doing a volume mount from the Docker host to the container on /etc/mysql/conf.d. But the problem is that the container image you’re using may …

Schema changes are the big challenges in Galera replication. So, it is recommended to understand the schema changes operation for everyone who uses the Percona XtraDB Cluster (PXB)/Galera clusters. In this blog, I am going to explain the operation and impact of the various schema changes methods used in the PXB/Galera cluster.

• Schema changes with “wsrep_OSU_method = TOI”
• Schema changes with “wsrep_OSU_method = RSU”
• Schema changes with “ONLINE ALGORITHMS”
• Schema changes with “pt-osc”
• Schema changes with “gh-ost”

For testing:

• I have configured the 3-node Percona Xtradb Cluster (8.0.19).
• Executing read/write load using the sysbench.

mysql> select @@wsrep_cluster_address\G
*************************** 1. row …

After spending four years working with ProxySQL in production, I’ve learned a few interesting lessons about interpreting and processing query rules. I hope to save you some time (and avoid wrong turns) with this summary of ProxySQL query rules.

ProxySQL query engine is very powerful and supports the building of complex rule sets. These can be used to route traffic to backend MySQL instances, rewrite queries, and for traffic mirroring, among other use cases.

When the rule set is short and simple, you can easily understand what the outcome for a certain query would be. However, for complex sets or combined scenarios, you need a deeper understanding of the engine logic.

Note 1: Rules are processed in rule_id order

It might seem like a trivial start, but during testing or implementation, …

We sometimes receive challenging requests… this is a story about one of those times.

The customer has implemented a sharding solution and would like us to review alternatives or improvements. We analyzed the possibility of using ProxySQL as it looked to be a simple implementation. However, as we had 200 shards we had to implement 200 rules — the first shard didn’t have much overload, but the latest one had to go through 200 rules and took longer.

My first idea was to use FLAGIN and FLAGOUT creating a B-Tree, but the performance was the same. Reviewing the code, I realized that the rules were implemented as a list, which means that, in the end, all the rules were going to be processed until hit with the right one and FLAGIN is used just to filter out.

At that point, I asked, what could I do? Is it possible to implement it differently? What is the performance impact?

One Problem, Two Solutions

I …

PMM (Percona Monitoring and Management) is a great community tool for monitoring your OSDB (MySQL, PostgreSQL, MongoDB) fleet. It’s feature rich, and it’s built and distributed as open-source based on several de-facto industry standard tools such as Grafana and Prometheus. In the second half of last year, major version 2 was released and whereas the major components remained mostly the same, some significant architectural changes were made, but this is out-of-scope for this post.

Upgrading to PMM2 is basically the same as starting from scratch with a fresh install; it requires re-adding all your servers, which can be a painful process if you have a large fleet of instances. For servers where you have OS level access, you can just install the PMM2 agent, but for RDS there is no access to the OS so another approach is required. In this blog, I will focus on getting a large number of RDS instances added.

Adding RDS instances …

In my day to day tasks as a DB Engineer at Mydbops we have been using multiple MySQL tools for multiple use cases to ensure an optimal performance and availability for servers managed by our Remote DBA Team.

A tool like pt-online-schema can be used for any DDL changes ( Overview to DDL algorithm ), if any tool which needs to scheduled for longer period we tend to use screen or cron.

Some of the problems we face when we demonise the process or use screen for running processes.

• The daemon process gets killed when the server reboot happens. …

Ever wanted to extend MySQL and add some feature you think it is missing?  With MySQL plugins, you can do exactly that.  One thing that has bothered me for several years is that you cannot easily retrieve system metrics from within MySQL.  Whether I am connecting via a remote connection or looking to add features to monitoring without the need for another interface with the server, I have wanted to retrieve system metrics without leaving the MySQL interface.

So, I started a Proof of Concept for this.  My goal was to get metrics such as RAM (total, used, free), system load, CPU utilization, disk utilization for the file system containing the datadir, and more.  My objective was to do this as efficiently within MySQL as possible.  For this, I chose to utilize standard C libraries in as few lines of code as possible without having to scrape system files or run commands to get the data.  The …

Oracle MySQL is in need of a columnar storage engine for analytics workloads.  A columnar engine (or column store) stores data vertically, that is, it stores all the data associated with a column together, instead of the traditional RDBMS storage method of storing entire rows together, either in a index organized manner, like InnoDB, or in a heap, like MyISAM.  

Columnar storage has the benefit of reducing IO when only a subset of the row is accessed in a query, because only the data for the accessed rows must be read from disk (or cache) instead of having to read entire rows.  Most columnar stores do not support indexes, but WARP does.

WARP is open source

You can find the WARP source code release on GitHub.  Binaries can be provided upon request.  Simply open an issue for your desired Linux distribution, and I will make them available as soon as I can.

…

Join Sveta Smirnova, MySQL Engineer at Percona, as she discusses modern solutions for modern database loads.

MySQL is famous for working well in high performing environments. This is the reason why it is the most popular backend for web applications. But our view of what to call high-performance changes over the cycles. Every year we get faster data transfer speed; more devices, connected to the Internet; more users and, as a result, more data.

The challenges MySQL developers have to solve are getting harder over time.

In this session, Sveta will show how use-case scenarios are changing over 25 years of MySQL history. She will show what did MySQL engineers do to keep the product up to date and cover topics such as handling a large number of active connections and high volumes of data as well as how the latest MySQL versions handle increased load better.

After attending this …