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MySQL 5.7 reads all your binlog files more often than you think

After upgrading some of our slaves to latest 5.7, I have found  what looks like a serious regression introduced in MySQL 5.7. 
A couple weeks ago I noticed that the error log file of one of our clusters, where I had implemented my in place transparent compression of binary logs,  was literally flooded by the following error:

[ERROR] Binlog has bad magic number;  It's not a binary log file that can be used by this version of MySQL
 
In the above setup this is  an harmless error, and it should only happen at server startup, where mysqld opens and reads all available binary log files.  The error is due to the fact that since files are now compressed, mysqld doesn't recognize them as valid - not an issue, as only older files are compressed, and …

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Ulimit conflict with PAM and Systemd​​​

As a part of the MySQL Support, we had a support request from a client.The issue is DB server runs out of open files limit, though it is configured. It causes the DB hang and crash at times. Sometimes they can’t able to fix. So we plan to write our experience with configuring. We believe this article can help in configuring appropriate Ulimit value without any obstacles. Let us jump to the subject. What are the errors we might face while ulimit is not properly configured?

  1. Too many open files
  2. System unable to allocate necessary resources for the monitor thread
  3. can’t create new thread, closing connection

The above-shared list is just sample’s, maybe people who currently reading this blog may also face issue related to ulimit, for that they may have different debug …

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Fun with Bugs #58 - Bug of the Day From @mysqlbugs

In 2013 I had a habit of writing about MySQL bugs on Facebook almost every day. Typical post looked like this one, link to the bug and few words of wondering with a bit of sarcasm.
By the way, check last comments in Bug #68892 mentioned there - the problem of LOST_EVENTS in master's binary log and a way to workaround it still valid as of MySQL 5.7.17.At that time I often got private messages from colleagues that Facebook is a wrong media for this kind of posts, these posts make MySQL look "buggy" etc, and eventually I was shut up

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Running simultaneous queries with Python, for killing them

This topic is about, simple approach to run multiple sql statements for testing XtraBackup behaviour – if it is going to kill them due to blocked FTWRL(FLUSH TABLES WITH READ LOCK).

According to the DOC -> Backup Locks

Percona Server has implemented this feature to be a lightweight alternative to FLUSH TABLES WITH READ LOCK for both physical and logical backups. Three new statements are now available: LOCK TABLES FOR BACKUP, LOCK BINLOG FOR BACKUP and UNLOCK BINLOG.

So by default, if you are using PS it is going to use LOCK TABLES FOR BACKUP prior copying non-InnoDB tables.

Well, how to force to use FTWRL instead of Backup Locks?
Congratulations – we have --no-backup-locks option, if you specify it, the FTWRL will be used.

Okay, again reading the DOC …

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Posting to Telegram channel by bot using mysql, python

Idea to create channel in the telegram came me from my friend. I have a lot of  useful electronic materials about programming, and he offered me to share them in telegram channel. To create channel is very easy. But share materials manually is very boring and wasting time. That’s why I’ve decided to automate it using mysql and python. First of all I’ve created table in the mysql to store my books there. And then i’ve created my first bot in telegram. Documentation of telegram bots: https://core.telegram.org/bots

Also you can find API documentation of telegram bots here: https://core.telegram.org/bots/api

And than was created channel. You can learn how to create channel from here:  …

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MySQL Enterprise Monitor 3.4.5 has been released

We are pleased to announce that MySQL Enterprise Monitor 3.4.5 is now available for download on the My Oracle Support (MOS) web site. This is a maintenance release that includes a few new features and fixes a number of bugs. You can find more information on the contents of this release in the change log.

You will find binaries for the new release on My Oracle Support. Choose the "Patches & Updates" tab, and then choose the "Product or Family (Advanced Search)" side tab in the "Patch Search" portlet.

Important: MySQL Enterprise Monitor (MEM) 4.0 offers many significant improvements over MEM 3.4 and we highly recommend that you consider upgrading. More information on MEM 4.0 is available here:

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Percona Server for MySQL 5.6.38-83.0 is Now Available

Percona announces the release of Percona Server for MySQL 5.6.38-83.0 on December 8, 2017. Download the latest version from the Percona web site or the Percona Software Repositories. You can also run Docker containers from the images in the Docker Hub repository.

Based on MySQL 5.6.38, and including all the bug fixes …

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MySQL Connector/NET 6.10.5 GA has been released

Dear MySQL users,

MySQL Connector/Net 6.10.5 is the second GA release and the first to
introduce .NET Core 2.0 and Entity Framework Core 2.0 support.

To download MySQL Connector/Net 6.10.5 GA, see the “Generally Available
(GA) Releases” tab at http://dev.mysql.com/downloads/connector/net/

Changes in MySQL Connector/Net 6.10.5 (2017-12-08, General
Availability)

   Functionality Added or Changed

     * Support for .NET Core 2.0 and .NET Standard 2.0 has been
       added (.NET Core 1.1 support continues). With .NET Core 2.0, most
       of the common ADO.NET classes are available for use, such as:

          + System.Data.DataTable, System.Data.DataColumn, and
            System.Data.DataRow

          + System.Data.DataSet

          + System.Data.Common.DataAdapter

     * Support for Entity Framework Core …
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This Week in Data with Colin Charles 18: Percona Live Call For Papers and a MongoDB 3.6 Overview

Join Percona Chief Evangelist Colin Charles as he covers happenings, gives pointers and provides musings on the open source database community.

I highly recommend submitting to the CFP for Percona Live Santa Clara 2018 even though it only closes December 22 2017. By the 3rd week of December, i.e. before the CfP closes, it is very likely that we will announce some of the schedule. So get in early! Keep in mind the broad topics, there are some ideas here.

Also: we are looking for sponsors for Percona Live – you can email me for more information.

Releases

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Data Modelling: A Counter Table

A counter table is a table that keeps counts of particular items or for certain keys. This can range from page count on your blog to keep track of a limit the user is allowed to have from a particular item or service.

Usually, a counter table would be better kept in something like Memcached or Redis as frequent increment updates would be better suited to those in-memory systems.

MySQL and Innodb in particular has many stringent systems to make sure that your data has been reliably written to disk. Just going through those systems alone, can make having a counter table, not suitable, not even considering the speed it takes to update the actual table.

However, sometimes there is a need for certain assurances from failure scenarios where in-memory systems may not be suitable for - as when they crash, the data kept in memory is cleared out.

In those cases, may I recommend that you do what I …

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