FOSDEM is next weekend and I am talking about Parallel Replication on Friday, February 2nd at the MySQL Pre-FOSDEM Day (there might be tickets left in case of cancellation, attendance is free of charge).  During this talk, I will show benchmark results of MySQL 8.0 parallel replication on Booking.com real production environments.  I thought I could share a few things before the talk so here it

In this blog post, I’ll talk about multi-threaded slave statistics printed in MySQL error log file.

MySQL version 5.6 and later allows you to execute replicated events using parallel threads. This feature is called Multi-Threaded Slave (MTS), and to enable it you need to modify the

slave_parallel_workers

 variable to a value greater than 1.

Recently, a few customers asked about the meaning of some new statistics printed in their error log files when they enable MTS. These error messages look similar to the example stated below:

[Note] Multi-threaded slave statistics for channel '': seconds elapsed = 123; events assigned = 57345; worker queues filled over overrun level = 0; waited due a Worker queue full = 0; waited due the total size = 0; waited at clock conflicts = 0 waited (count) …

Yes, another post about my talks at Percona Live Santa Clara: I obviously still have things to share.  This time, I will focus on my parallel replication talks by giving a short preview.

I have two parallel replication talks at Percona Live:

MySQL/MariaDB Parallel Replication: inventory, use cases and limitations (Wednesday talk) MySQL Parallel Replication: all the 5.7 (and some of the 8.0)

In a previous post, I listed all the Booking.com talks at Percona Live.  In this post, I will give more details about my talks.

As a reminder, the list of my talks is the following:

Monitoring Booking.com without looking at MySQL (Thursday keynote) The two little bugs that almost brought down Booking.com (Tuesday Lightning Talk) MySQL/MariaDB Parallel Replication: inventory, use cases and

In a week, me and some Booking.com colleagues will be in Santa Clara for Percona Live.

Booking.com is sponsoring the conference and we will be present at the Monday Evening Reception.  You do not need a tutorial pass to attend the dinner (even if it is on the tutorial day): any valid pass will do.  If you do not have your ticket yet, it is time to register (you can use the discount code “

MySQL 5.7 introduced the LOGICAL_CLOCK type of multi-threaded slave (MTS).  When using this type of parallel replication (and when slave_parallel_workers is greater than zero), slaves use information from the binary logs (written by the master) to run transactions in parallel.  However, enabling parallel replication on slaves might not be enough to get a higher replication throughput (VividCortex

I have a new blog post on blog.booking.com describing MariaDB 10.1 Optimistic Parallel Replication (with benchmark results):

Evaluating MySQL Parallel Replication Part 4: More Benchmarks in Productionhttp://blog.booking.com/evaluating_mysql_parallel_replication_4-more_benchmarks_in_production.html

If you want to know more about MySQL/MariaDB Parallel Replication and if you are attending 

Reminder: MTS = Multi-Threaded Slave.

Update 2017-04-17: since the publication of this post, many things happened:

the procedure for fixing a crashed slave has been automated (Bug#77496) Bug#80103 as been closed at the same time as Bug#77496 but I still think there are unfixed things, see Bug#81840

End of update 2017-04-17.

I will be talking about parallel replication at FOSDEM in Brussel on

My webinar “Multi-threaded Replication in MySQL 5.6 and 5.7″ on February 25 generated several excellent questions following the presentation (available here for playback along with the slides). I didn’t have time to answer many of the questions during the session and so in this post I answer all of them. Thanks to everyone who attended!

Q: What do you expect from MTS with logical clock? Do you think performance would be good as with per database?
A: MTS with 5.6 is not usable if you have a single database. I do not have numbers, but this is quite frequent. With 5.7 everyone should be able to benefit from multi-threaded replication.

Q: When MySQL 5.6 was released, performance of MTS was lower, than in 5.5, for example. Is this addressed now?
A: I am not sure which …

In a previous post, titled “Multi-threaded replication with MySQL 5.6: Use GTIDs,” I explained that using GTID replication is almost a requirement when using MySQL 5.6 MTS. Let’s see now how to perform the day-to-day operations when MTS and GTIDs are both enabled. (I’ll also be presenting a related webinar next week titled “Multi-threaded Replication in MySQL 5.6 and 5.7″).

Seeing the execution gaps

If you have a look at SHOW SLAVE STATUS while the slave is running, you may not be expecting such an output:

[...]
Executed_Gtid_Set: …