Showing entries 1 to 10 of 149
10 Older Entries »
Displaying posts with tag: bugs (reset)
Fun With Bugs #50 - On Bugs Tagged as "missing manual"

Back in January 2014, some time after many nice people kindly asked me to shut up stop writing about MySQL bugs on Facebook several times per day, I decided to start reading the fine MySQL Manual more carefully than before and report not only typos there, but also any topic or detail not properly explained. Usually these reports, tagged as "missing manual", were the result of careful study of the documentation based on real user question or customer issue. So, most of these reports came from real life, and missing information badly affected poor MySQL users.

Today, for this issue #50 in my series of posts about MySQL bugs, I decided to list and …

[Read more]
Fun with Bugs #49 - Applying PMP to MySQL

As you maybe noted, in several recent posts I've provided some additional details for slides used during my FOSDEM talk on profiling MySQL. The only part not covered yet is related to using Poor Man's Profiler (and pt-pmp version of it). I see no reason to explain what it does and how to use it once again, but would like to show several recent enough MySQL bug reports where this tool was essential to find, explain or demonstrate the problem.

[Read more]
MySQL Support Engineer's Chronicles, Issue #5

A lot of time passed since my previous post in this series. I was busy with work, participating in FOSDEM, blogging about profilers and sharing various lists of MySQL bugs. But I do not plan to stop writing about my usual weeks of doing support engineer's job. So, time for the next post in this series, based on my random notes taken during the week here and there.

This week started for me with checking recent MySQL bug reports (actually I do it every day). …

[Read more]
Fun with Bugs #48 - Group Replication Bugs and Missing Features as of MySQL 5.7.17

It seems recent post on Group Replication by Vadim caused an interesting discussion on Facebook. I am NOT going to continue it here, but decided to present some facts, specifically, list of public bug reports and feature requests for Group Replication (mostly "Verified", that is, accepted by Oracle engineers as valid) as of MySQL 5.7.17 (where the feature is promoted as GA), with just few comments to some of the bugs.

The goal is to double check this post when next Oracle MySQL 5.7.x release appears, to find out how much Oracle carews to fix the problems already identified by MySQL Community.

So, here are the bugs and feature requests in …

[Read more]
MySQL super_read_only Bugs

This blog we describe an issue with MySQL 5.7’s super_read_only feature when used alongside with GTID in chained slave instances.

Background

In MySQL 5.7.5 and onward introduced the gtid_executed table in the MySQL database to store every GTID. This allows slave instances to use the GTID feature regardless whether the binlog option is set or not. Here is an example of the rows in the gtid_executed table:

mysql> SELECT * FROM mysql.gtid_executed;
+--------------------------------------+----------------+--------------+
| source_uuid                          | interval_start | interval_end | …
[Read more]
Profiling MyRocks with perf: Good Old Bug #68079 Use Case

Almost a year ago I've got really interested in MyRocks and built MySQL from Facebook that provides it from source. Since that time I build it from fresh sources few times per week (as I've described in that post) and once in a while try to work with it and study some details or use cases. Today I'd like to discuss one of them that I've recently studied with perf profiler.

This is not only because I am going to talk about applying profilers to all kinds and forks of MySQL at FOSDEM 2017 MySQL & Friends …

[Read more]
perf Basics for MySQL Profiling

Oprofile was widely used for MySQL profiling on Linux in the past. But since 2010 and 2.6.31 Linux kernels another profiler, perf, gets increasing popularity. It uses performance counters (CPU hardware registers that count hardware events such as instructions executed) subsystem in Linux. perf is capable of lightweight profiling. It is included in the Linux kernel, under tools/perf (so features available depends on kernel version), and is frequently updated and enhanced.

So, probably perf is the future of profiling on Linux and it makes sense to discuss its basic usage for profiling MySQL servers. For detailed discussions of features provided, numerous examples (not related to MySQL) and links I suggest to read …

[Read more]
When MySQL Lies: Wrong seconds_behind_master with slave_parallel_workers > 0

In today’s blog, I will show an issue with seconds_behind_master that one of our clients faced when running slave_parallel_works > 0. We found out that the reported seconds_behind_master from SHOW SLAVE STATUS was lying. To be more specific, I’m talking about bugs #84415 and #1654091.

The Issue

MySQL will not report the correct slave lag if you have slave_parallel_workers> 0. Let’s show it in practice.

I’ll use MySQL Sandbox to speed up one master and two slaves on MySQL version …

[Read more]
MySQL Support Engineer's Chronicles, Issue #4

This week I had to deal with some unusual problems. But let me start with Percona's xtrabackup, software that I consider a key component of many current production MySQL setups and use regularly. Recently new minor versions of XtraBackup were released, check the details on 2.4.5, for example. It made a step towards support of MariaDB 10.2, but it's still a long way to go, see this pull request #200.

My main problem with xtrabackup, though, is not with lack of support of MariaDB 10,2-specific features. Why should they care, after all... The problem is that old well known bugs and problems are not resolved, those that may affect all MySQL versions, forks and environments. Check  …

[Read more]
MySQL Support Engineer's Chronicles, Issue #3

The original idea of this series was to publish one post per week, but it seems every other week I have some special topic that well deserves a dedicated post. Last week I had no time to complete my writing because of long (and, I hope, useful) Howto post on replacing corrupted partition using non-corrupted one from other server in replication setup. But I had links and notes collected in a draft that I am going to complete now.

First of all, during the previous week I had time to submit two more talks for the  …

[Read more]
Showing entries 1 to 10 of 149
10 Older Entries »