As follow up to the regular shows announcements, we would like to inform you about places & shows where you can find MySQL Community team or MySQL experts at during March to May 2020 timeframe. Please find the details with a list of MySQL talks & booth details (if available at this time) below:

• March 2020:

  • Southern California Linux Expo (ScaLE), Pasadena, US, March 5-8, 2020

    • MySQL talk: "MySQL New Features for Developers" by David Stokes, the MySQL Community Manager. 
      • Timing: Friday, March 6, 2020 - 15:15 to 16:00
      • Room: 101
    • Booth: please find us in the expo …

There are a lot of things I love about Prometheus; its data model is fantastic for monitoring applications and PromQL language is often more expressive than SQL for data retrieval needs you have in the observability space. One thing, though, I hate about Prometheus with a deep passion is the behavior of its rate() and similar functions, deeply rooted in the Prometheus computational model, which I was told by the development team is not likely to change.

So What’s the Problem, and Why is it Such a Big Deal?

First – the problem.  rate() functions give you the rate of change of the time series for the Interval supplied, so rate(mysql_global_status_questions[10s]) will basically give us the average number of MySQL questions over the last 10seconds. Everything is great so far.

But what if the resolution of this time series is lower than 10 seconds, for example, if we take …

I will try to make it short and clear: if you are writing SQL queries with “NOT IN” like
SELECT … WHERE x NOT IN (SELECT y FROM …)
you have to be sure to first understand what happens when “x” or “y” are NULL: it might not be what you want!…

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This blog is about one of the issues encountered by our Remote DBA Team in one of the production servers. We have a setup of MySQL 5.7 Single Primary (Writer) GR with cluster size of  3 . Due to OOM, the MySQL process in the primary node got killed, this repeated over the course of the time.

We all know about the OOM (out of memory), theoretically, it is a process that the Linux kernel employs when the system is critically low on memory.

In a dedicated DB server, when the OOM triggers the direct impact will be on mysqld process since it will be the most memory consuming one.

Going forward will look into the detailed analysis made to tackle the issue of OOM.

DB Environment:-

• Service – Group Replication Cluster
• Cluster Nodes – 3
• GR mode – Single Primary …

Thanks Oystein Grovlen for your comment .

Yes Sir, I understand and completely agree with your point .

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In reply to hercules7sakthi.

Justin’s point is that you chose to explicitly commit the transaction after the failure. You had the choice to to repeat the statement or roll back to maintain atomicity.

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In reply to Justin Swanhart.

Hi Justin,

Thanks for your comment . Our applications has the proper error handling mechanism to handle the failures .

I had the issue, when I tested the variable innodb_rollback_on_timeout with different threshold ( ON and OFF ). The complete flow was documented in this blog . And, there is no deadlock happens , it is a LOCK WAIT TIMEOUT .

Even the document says “InnoDB rolls back only the last statement on a transaction timeout by default.”

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Your application should retry the update or roll back. InnoDB is not losing atomicity. You commit a transaction with changes and that os just a bug in your app. Note that InnoDB always rolls back whole transactions on deadlock. Your application has to handle failed statements.

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The blog title seems something crazy ?

Yes, by default your InnoDB transactions don’t have the Atomicity . But, you can control the atomicity of your InnoDB transaction with the variable innodb_rollback_on_timeout. We had a weird data inconsistency issue within the transaction . In this blog , I am going to explain “How it will happen?” and “How it can be fixed ?” .

Whats is Atomicity ?

From Wiki ,

Transactions are often composed of multiple statements. Atomicity guarantees that each transaction is treated as a single “unit”, which either succeeds completely, or fails completely: if any of the statements constituting a transaction fails to complete, the entire transaction fails and the database is left unchanged.

What is …

MySQL Connector in 8.0.19 includes the support of DNS SRV.

The following URL can be a good starting point to understand what this feature is about.


https://www.slideshare.net/Grypyrg/mysql-connectors-8019-dns-srv

https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-dns-srv.html

https://learn.hashicorp.com/consul/security-networking/forwarding


MySQL Router in MySQL InnoDB Cluster setup offers the transparent access to the backend database servers.   However, the application has to know the IP Address of the Router in order to get …