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Displaying posts with tag: performance_schema (reset)
Dynamic Tracing of MySQL Server With perf probe - Basic Example

I am going to write a series of blog posts based on my talks and experiences at Percona Live Europe 2019. The first one would be a kind of extended comment for a couple of slides from the "Tracing and Profiling MySQL" talk.

We can surely wait until Performance Schema instruments every other line of code or at least every important stage and wait in every storage engine we care about, but there is no real need for that. If you run any version of MySQL under Linux with more or less recent kernel (anything newer than 4.1 is good enough, in general), you can easily use dynamic tracing for any application (at least if there is symbolic information for the binaries), any time. As Brendan Gregg put it here:

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Fun with Bugs #89 - On MySQL Bug Reports I am Subscribed to, Part XXIII

I have to celebrate the anniversary of my last day in Oracle (that was 7 years ago!) somehow, and I think writing yet another blog post about Oracle MySQL bugs is a good way to do this. I am actually surprised (and happy) that public bugs database is still alive, maintained and considered important in Oracle, and I know who in Oracle was working hard all these years for this to happen!

In my previous post in this series I've stopped on Bug #95954 and had not completed review of interesting MySQL bug reports that I've subscribed to in June 2019. So, below I start with the next bug in my list, complete review for June and cover some bugs reported in July. There were many.

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MySQL 8.0: if I should optimize only one query on my application, which one should it be ?

Answering this question is not easy. Like always, the best response is “it depends” !

But let’s try to give you all the necessary info the provide the most accurate answer. Also, may be fixing one single query is not enough and looking for that specific statement will lead in finding multiple problematic statements.

The most consuming one

The first candidate to be fixed is the query that consumes most of the execution time (latency). To identify it, we will use the sys schema and join it with events_statements_summary_by_digest from performance_schemato retrieve a real example of the query (see this post for more details).

Let’s take a look at what sys schema has to offer us related to our mission:

> show tables like …
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MySQL 8.0 Memory Consumption on Small Devices

Recently, PeterZ pointed a huge difference in memory usage of MySQL 8.0 compare to MySQL 5.7. This can be an issue for small instances if the same configuration for buffers like the buffer pool are not changed.

As explained in Peter’s article, this can lead to the awakening of the so feared OOM Killer !

MorganT, pointed accurately in his comment what is the source of such difference and how this was then caused by the new instrumentation added in MySQL 8.0.

Nothing is free, even as a …

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MySQL InnoDB Cluster : Recovery Process Monitoring with the MySQL Shell Reporting Framework

As explained in this previous post, it’s now (since 8.0.16) possible to use the MySQL Shell Reporting Framework to monitor MySQL InnoDB Cluster.

Additionally, when a member of the MySQL InnoDB Cluster’s Group leaves the group for any reason, or when a new node is added from a backup, this member needs to sync up with the other nodes of the cluster. This process is called the Distributed Recovery.

During the Distributed Recovery, the joiner receives from a donor all the missing transactions using asynchronous replication on a dedicated channel.

It’s of course also possible to monitor the progress of this recovery process by calculating how many transactions have …

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Using the new MySQL Shell Reporting Framework to monitor InnoDB Cluster

With MySQL Shell 8.0.16, a new very interesting feature was released: the Reporting Framework.

Jesper already blogged about it and I recommend you to read his articles if you are interested in writing your own report:

  • https://mysql.wisborg.dk/2019/04/26/mysql-shell-8-0-16-built-in-reports/
  • https://mysql.wisborg.dk/2019/04/27/mysql-shell-8-0-16-user-defined-reports/

I this post, I will show you one user-defined report that can be used to monitor your MySQL InnoDB Cluster / Group Replication.

Preparation

Before being able to use the report, you need to download 2 files. The first one is the …

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What configuration settings did I change on my MySQL Server ?

This post is just a reminder on how to find which settings have been set on MySQL Server.

If you have modified some settings from a configuration file or during runtime (persisted or not), these two queries will show you what are the values and how they were set. Even if the value is the same as the default (COMPILED) in MySQL, if you have set it somewhere you will be able to see where you did it.

Global Variables

First, let’s list all the GLOBAL variables that we have configured in our server:

SELECT t1.VARIABLE_NAME, VARIABLE_VALUE, VARIABLE_SOURCE
FROM performance_schema.variables_info t1
JOIN performance_schema.global_variables t2
ON t2.VARIABLE_NAME=t1.VARIABLE_NAME
WHERE t1.VARIABLE_SOURCE != 'COMPILED';

This is an example of the output:

Session Variables

And now the same query for the session variables:

SELECT t1.VARIABLE_NAME, VARIABLE_VALUE, …
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Fun with Bugs #84 - On Some Public Bugs Fixed in MySQL 5.7.26

Oracle released minor MySQL Server versions in all supported branches on April 25, 2019. MySQL 5.7.26 is just one of them, but recently I prefer to ignore MySQL 8 releases (after checking that I can build them from source code at least somewhere, even if it takes 18G+ of disk space and that they work in basic tests), as there are more chances for MySQL 5.7 bug fixes to affect me (and customers I care about) directly.

So, in this yet another boring blog post (that would never be a reason for any award) I plan to concentrate …

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Fun with Bugs #75 - On MySQL Bug Reports I am Subscribed to, Part XII

From the lack of comments to my previous post it seems everything is clear with ERROR 1213 in different kinds and forks of MySQL. I may still write a post of two about MyRocks or TokuDB deadlocks one day, but let's get back to my main topic of MySQL bugs. Today I continue my series of posts about community bug reports I am subscribed to with a review of bugs reported in November, 2018, starting from the oldest and skipping those MySQL 8 regression ones I've already commented on. I also skip documentation bugs that should be a topic for a separate post one day (to give more illustration to …

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pre-FOSDEM MySQL Day 2019

For the third year in a row, we will take advantage of the mass presence of our MySQL Engineers during FOSDEM to organize the pre-FOSDEM MySQL Day.

The program of this 3rd edition is already on track, thank you to all the speakers who already confirmed their participation.

Start End Event Speaker Company Topic
Friday 1st February
09:30 10:00 MySQL Community Team Welcome
10:00
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