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Some time ago I finally had the chance to test the built-in load balancing feature in MySQL's JDBC driver together with a 3 node Galera cluster. I have used this feature at a MySQL Cluster customer many years ago, so I knew it worked and I knew it was great, but I didn't know if it would work with Galera. Galera sometimes returns some error states that are different from what MySQL Cluster does and the main point of the test was to see how the loadbalancing in the JDBC driver reacts to that.
On Thursday I went to the Harmony conference arranged by Oracle User Group Finland to speak about Galera clustering. (They chose the topic based on my suggestions.) The slides are now available on SlideShare. I'm pretty satisfied with this talk myself, the slides contain the most important steps you need to know to get started, but also the internal architecture of Galera, how it works, and what kind of replication topologies and load balancing you would want to use with it. And benchmarks of course.
Heli from Oracle User Group Finland invited me to speak at this years OUGF Harmony conference which starts tomorrow. Last year I had some proposals accepted but had to decline due to work travel.
This year they wanted to learn more about Galera and I was of course more than happy to go and speak. My talk is titled "Synchronous Multi-Master Clusters with MySQL: an Introduction to Galera." It contains some parts of what we presented at the MySQL Conference, but is more of an introduction and less about benchmarking.
This post is about a fairly technical detail of how Galera works. I'm writing it down in preparation for testing this feature so that I can agree with Alex whether to file a bug or not. I'm sharing it on my blog just in case someone else might benefit from learning this.
Galera 2.0 introduces rolling schema upgrades. This is a new way to do non-blocking schema changes in MySQL.
As the name suggests, it is done as a rolling upgrade. Having seen clusters doing rolling upgrades before, I assumed this is what happens:
Alex Yurchenko finally posted results on a benchmark he has planned to do for a long time: Galera vs NDB cloud shootout.
Their blog requires registration to comment, so I'll post my comment here instead:
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Sysbench can do the loadbalancing itself, so there is no need for external loadbalancer. Just add a comma separated list of master MySQL nodes to --mysql-host. This is similar to what the JDBC and PHP drivers can do too, and it is my favorite architecture. Why introduce extra layers of stuff that you don't need and that doesn't bring any additional value?
Synchronous multi-master replication with the Galera plugin. Your application connects to the load balancer and it redirects read/write traffic to the various MySQL Galera nodes. Tested a setup with 17 SQL nodes and you can have even more. Scaling reads and also a little bit for scaling writes is what Galera is good for.
If one node fails, the other two nodes still communicates with each other and the load balancer is aware of the failed node.
Why Galera? There is master-slave replication but its not multi-master, and its asynchronous and you can get inconsistencies. There is master-master replication but its asynchronous and can have inconsistencies and conflicts if you write on both nodes. MHA/MMM/Tungsten are
[Read more...]Just wanted to say I'm so happy: http://www.mysqlperformanceblog.com/2012/01/09/announcement-of-percona-x...
And also that this is a significant moment in the evolution of MySQL - things will never be the same again.
I've been promising I should re-visit once more the disk bound sysbench tests I ran on Galera. In December I finally had some lab time to do that. If you remember what troubled me then it was that in all my other Galera benchmarks performance with Galera was equal or much better compared to performance on a single MySQL node. (And this is very unusual wrt high availability solutions, usually they come with a performance penalty. This is why Galera is so great.) However, on the tests with a disk bound workload, there was performance degradation, and what was even more troubling was the performance seemed to decrease more when adding more write masters.
In these tests I was able to understand the performance decrease and it
[Read more...]Here are the slides to my first talk at Percona Live UK 2011: Choosing a MySQL High Availability solution.1
Many people have asked me what do I think was the best thing about Percona Live UK. I always answered: that it happened in the first place! This was the first time we had such a large and high-quality MySQL conference in Europe, and many well known bloggers and speakers that can't always travel to Santa Clara were present.
More importantly, many MySQL users who don't travel to Santa Clara could now see them speak and meet with them. I met at least 4 hard core MySQL DBA's from Helsinki that I've never met before. We had to travel to London to meet each other! (But if you are in Helsinki, we have our first MySQL user group tomorrow, this should fix things!)
When I walked into the conference venue, I introduced myself to a person that stood there
[Read more...]There are moments in history that become like signpost that everyone remembers the rest of their lives. Like where were you when you heard the news that JFK had been shot, or those 9/11 planes hit the WTC twin towers. If you work with MySQL and high-availability, then this week will be remembered as such. And if you're a European MySQL geek, you will remember that we were at the Percona Live UK conference when Galera clustering 1.0 was announced. Btw, the conference itself was also historical, at least for European MySQL users. I will have to write a separate blog post about the conference, because it was a great one, and I have to post slides of my 2 talks too. But this blog post is dedicated to the stable release of
[Read more...]Stockholm – October 25th 2011
Severalnines, provider of automation and management software for easily usable, highly available and auto-scalable cloud database platforms, today announces the release of ClusterControl™ for MySQL Galera in cooperation with Codership, the replication experts organisation that leverages the latest developments in computer science to produce fast and scalable synchronous replication solutions that "just work" for databases and similar applications.
Introducing ClusterControl™ for MySQL Galera
Blackhole tables are often used on a so-called “relay slave” where some operation needs to happen but no data needs to exist. This used to have a bug that prevented AUTO_INCREMENT columns from propagating the right values through replication, but that was fixed. It turns out there’s another bug, though, that has the same effect. This one is caused when there is an INSERT into a Blackhole table, where the source data is SELECT-ed from another Blackhole table.
I think it’s wise to keep it simple. MySQL has tons of cool little features that theoretically suit edge-case uses and make ninja tricks possible, but I really trust the core plain-Jane functionality so much more than these edge-case features. That’s precisely because they
[Read more...]Suomeksi: MySQL käyttäjätapaaminen Helsingissä 1. marraskuuta. Klikkaa allaolevaa linkkiä ilmoittautuaksesi, siellä saat myös lisätietoa suomeksi.
Finally it's here! So many of you have always asked about it. Markus and other Elisa guys. Osma and Ilkka at Habbo Hotel. And others... MySQL was born in Helsinki, InnoDB was born in Helsinki, a lesser known database / also MySQL engine called Solid was born in Helsinki, and 2 great replication companies, Continuent with multiple generations of clustering for MySQL, and Codership with Galera, are Helsinki companies. And amidst this embarrassment of riches, what did we not have?
A MySQL User Group.
Team Codership will give a Galera presentation in the next event of the distinguished PerconaLive conference series in London (Oct 25).I'm looking at the schedule for Percona Live UK coming up in 2 weeks from now and realize there's quite a smorgasbord of High Availability talks. What's more interesting, I see that we will be presenting some opposite opinions for the audience to digest:
Update 2012-01-09: I have now been able to understand the poor(ish) results in this benchmark. They are very likely due to a bad hardware setup and neither Galera nor InnoDB is to blame. See http://openlife.cc/blogs/2012/january/re-doing-galera-disk-bound-benchmark
People commenting on my results for benchmarking Galera on a disk bound workload seemed to be confused by the performance degrading when writing to more than one master, and not convinced at my speculations on the reasons. Since sysbench 0.5 has the benchmarks in the form of LUA scripts, it was temptingly easy to tweak those a little to see if my speculations were correct. So yesterday I did run tests again with a
[Read more...]2 concepts I've been an active advocate of during the past few years are both supported by Galera: Multi-threaded (aka parallel) slave, and allowing out-of-order commits on such a parallel slave. In trying to optimize Galera settings for the disk bound workload I just reported on, I also came to test these alternatives.
All of my previously reported tests have been run with wsrep_slave_threads=32. For the memory-bound workload there was no difference using one thread or more, but I left it at 32 "just in case". For the disk bound workload there is a clear benefit in having a multi-threaded slave:
Update 2012-01-09: I have now been able to understand the poor(ish) results in this benchmark. They are very likely due to a bad hardware setup and neither Galera nor InnoDB is to blame. See http://openlife.cc/blogs/2012/january/re-doing-galera-disk-bound-benchmark
After getting very good results with Galera with using a memory bound workload, I was eager to then also test a disk bound workload. Also this time I learned a lot about how Galera behaves and will try to share those findings here.
The setup for these tests is exactly the same as in last weeks
[Read more...]So, vacation is over and I was in luck: Already during first week I had ample time to finally put Galera replication to the test. It was a great experience: I learned a lot, and eventually got the great results I was hoping to see.
Again I've started by just running the standard Sysbench oltp read-write test. Since this is a commonly used benchmark, it produces numbers that are comparable with others running the same benchmarks. Including, as it happens, Galera developers themselves.
These tests were run on an 8 core server with 32 GB of RAM and the disk on some EMC device with a 2,5GB write cache.
A while ago Baron blogged about his utter dislike for MMM, a framework supposedly used as a MySQL high-availability solution. While I have no personal experience with this framework, reading the comments to that blog I'm indeed convinced that Baron is right. For one thing, it includes the creator of MMM agreeing.
Baron's post still suggests - and having spoken with him I know that's what he has in mind - that a better solution could be built, it's just MMM that has a poor design. I'm going to go further than that: Personally, I've come to think that this family of so called clustering suites is just categorically the wrong approach to database high-availability. I will now explain why they fail, and what the right way is instead.
I've been following the Galera project for years now, but this week I finally had some time to spend hands on time on it. I'm sure you noticed Vadim from Percona is also looking at it, it will be interesting to compare results. In this post I will just share the experience of installing and configuring Galera.
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Couple of Fridays ago we had one of our @Inuits days again. Rather than having some people give talks and presentations about what they have been doing for the past couple of months this time we set out to research, test, and build stuff.
We split up in 3 different groups, one focusing on CI and testing freshly build stuff with cucumber, a second one setup and tested Galera
We setup a 3 node Galera cluster , not really as smooth as we'd like to ..
Our first bump was that the installation of the package on CentOS is hell, it needs manual interaction such as replacing packages. Deploying this from a repository is probably not going to be a straight forward option.
Galera only takes care of replicating data, just as with MySQL MM replication there still is a need for
[Read more...]
This Thursday (February 11th,
14:00 UTC), Seppo Jaakola & Alex Yurchenko will talk about MySQL Galera Multi-Master Replication. Galera provides synchronous multi-master replication and uses a
certification-based replication method for replicating transaction write sets in a DBMS cluster. The replication method requires close co-operation with database transaction processing and DMBS must support a specific replication API to be compatible with Galera. Codership has integrated Galera replication in the InnoDB storage engine, and the resulting MySQL/Galera cluster product has been published as a production-ready GA release in December 2009.
This Thursday (February 11th,
14:00 UTC), Seppo Jaakola & Alex Yurchenko will talk about MySQL Galera Multi-Master Replication. Galera provides synchronous multi-master replication and uses a
certification-based replication method for replicating transaction write sets in a DBMS cluster. The replication method requires close co-operation with database transaction processing and DMBS must support a specific replication API to be compatible with Galera. Codership has integrated Galera replication in the InnoDB storage engine, and the resulting MySQL/Galera cluster product has been published as a production-ready GA release in December
This Thursday (February 11th,
14:00 UTC), Seppo Jaakola & Alex Yurchenko will talk about MySQL Galera Multi-Master Replication. Galera provides synchronous multi-master replication and uses a
certification-based replication method for replicating transaction write sets in a DBMS cluster. The replication method requires close co-operation with database transaction processing and DMBS must support a specific replication API to be compatible with Galera. Codership has integrated Galera replication in the InnoDB storage engine, and the resulting MySQL/Galera cluster product has been published as a production-ready GA release in December
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