In a perfect world, we expect all software to run flawlessly and never have problems such as bugs and crashes. We also know that this perfect world doesn’t exist and we better be as prepared as possible to troubleshoot those types of situations. Historically, generating core dumps has been a task delegated to the kernel. If you are curious about how to enable it via Linux kernel, you can check out Getting MySQL Core file on Linux. There are a few drawbacks that pose either a limitation or a huge strain to get it working, such as:

• System-wide configuration required. This is not something DBA always has access to.
• Inability or very difficult to enable it for a specific binary only. Standards ways enable it for every software running on the box.
• Nowadays, with cloud and containers, this task has become even …

This blog discusses new features about the persisted system variables and how we can use it to make variable changes persistent. The MySQL server maintains system variables that control its operations. The dynamic variables used prior to the MySQL 8 release are not persistent and are reset upon restart. These variables can be changed at runtime using the SET statement to affect the operation of the current server instance but we have to manually update my.cnf config file to make them persistent. In many cases, updating my.cnf from the server-side is not a convenient option, and leaving the variable just updated dynamically reverts on the subsequent restart without any history.

Persisted system variables are one of the useful features introduced in MySQL 8. The new functionality helps DBAs update the variables dynamically and register them without touching the configuration files from the server-side.

How to Persist the Global …

If you often deploy services in the cloud, you certainly, at least once, forgot to stop a test instance. I am like you and I forgot my share of these. Another mistake I do once in a while is to provision a bigger instance than needed, just in case, and forget to downsize it. While this is true for compute instances, it is especially true for database instances. Over time, this situation ends up adding a cost premium. In this post, we’ll discuss a solution to mitigate these extra costs, the use of the RDS Aurora Serverless service.

What is Amazon Aurora Serverless?

Since last spring, Amazon unveiled a new database related product: RDS Aurora Serverless. The aim of this new product is to simplify the management around Aurora clusters. It brings a likely benefit for the end users, better control over cost. Here are some …

MySQL 8.0.22 was released on Oct 19, 2020, and came with nice features and a lot of bug fixes. Now, you can configure your async replica to choose the new source in case the existing source connection (IO thread) fails. In this blog, I am going to explain the entire process involved in this configuration with a use case.

Overview

This feature is very helpful to keep your replica server in sync in case of current source fails. 

To activate asynchronous connection failover, we need to set the “SOURCE_CONNECTION_AUTO_FAILOVER=1” on the “CHANGE MASTER” statement.

Once the IO connection fails, it will try to connect the existing source based on the “MASTER_RETRY_COUNT, MASTER_CONNECT_RETRY”. Then only it will do the failover. 

The feature will only work when the IO connection is failed, maybe the source crashed or stopped, or any network failures. This will not work if the replica is …

Earlier this week, Oracle released their Q4 releases series. As on the previous releases, backward compatibility has been broken with previous versions of the server. This time on both MySQL 5.7 and 8.0:

MySQL 5.7.32

While our QA team was performing an extensive test on it,  we found out this version introduced a new compression format version. This change breaks backward compatibility with older versions of MySQL, which is expected on the 8.0 series but is not on 5.7. As Percona XtraBackup (PXB) is based on MySQL code, it makes MySQL 5.7.32 incompatible with current versions of Percona XtraBackup 2.4.20 and prior.

The issue does not affect only Percona XtraBackup but also prevents users from downgrading the server from 5.7.32 to any lower version on the 5.7 series – More details at …

One of the most exciting storage-related features in Kubernetes is Volume snapshot and clone. It allows you to take a snapshot of data volume and later to clone into a new volume, which opens a variety of possibilities like instant backups or testing upgrades. This feature also brings Kubernetes deployments close to cloud providers, which allow you to get volume snapshots with one click.

Word of caution: for the database, it still might be required to apply fsfreeze and FLUSH TABLES WITH READ LOCK or

LOCK BINLOG FOR BACKUP

.

It is much easier in MySQL 8 now, because as with atomic DDL, MySQL 8 should provide crash-safe consistent snapshots without additional locking.

Let’s review how we can use this feature with Google Cloud Kubernetes Engine and …

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):

Recently I was dealing with an unexpected issue raised by our Support customer, in which data became inconsistent after a schema change was applied.

After some investigation, it turned out that affected tables had a special word in the comments of some columns, which triggered an already known (and fixed) issue with the TableParser.pm library of Percona Toolkit.  The problem is that the customer was using an outdated Toolkit version, where pt-online-schema-change was using that buggy parser.

This bug applies only to Percona Toolkit versions up to 3.0.10, so if you have already 3.0.11 or newer installed, you can skip the rest of this post as these are no longer affected.

I am writing this post to warn every user of pt-online-schema-change who has not upgraded the toolkit, as …

Visibility is a blessing, and with databases, visibility is a must. That’s true not only for metrics but for the queries themselves. Having info on all the stats around query execution is priceless, and Percona Monitoring and Management (PMM) offers that in the form of the Query Analytics dashboard (QAN).

But where to start? QAN helps you with that by calculating the query profile. What is the profile? It’s a rank of queries, ordered by Load, so it is easy to spot the heaviest queries hitting your database. The Load is defined as the “Average Active Queries” but can also be defined as a mix of Query Execution Time Plus Query count. In other words, all the time the query was alive and kicking.

The Profile in PMM 2.10.0 looks like this:

The purpose of this profile is to facilitate the task of finding the …

Hello everyone, in this little post we will review a new feature in MySQL 8.

What is “CHECK Constraint”?

This is a new feature to specify a condition to check the value before INSERT or UPDATE into a row. The constraint could return an error if the result of a search condition is FALSE for any row of the table (but not if the result is UNKNOWN or TRUE).

This feature starts working on MySQL 8.0.16, and in previous versions, we could create it, but it doesn’t work, meaning the syntax is supported but it is not working,

There are some rules to keep in mind…

– AUTO_INCREMENT columns are not permitted
– Refer to another column in another table is not permitted
– Stored functions and user-defined functions are not permitted (you can not call a function or any user-defined functions)
– Stored procedure and function parameters are not permitted (you cannot call …