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Failover is evil

In the Matrix movie there is a scene where the heroes visit a spiritual councelor, and amongst the people in her waiting room they see a little boy, dressed like a buddhist monk, who can bend a spoon just by looking at it. When they ask him what he does to bend the spoon, the boy's answer is: "There is no spoon". And if you watch the movie to the end, you will see that he is right. (In that spirit, if this post is too long to read for you, just skip to the last paragraph for the answer.)

The title for this blog post is of course inspired by Baron's "Is automated failover the root of all evil?", which is a commentary on GitHub's detailed explanation of their recent Pacemaker-induced downtime. Baron makes a good question, but the answer is deeper than suggested by the question. The problem is not the automation, the problem is the failover.

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OpenLife.cc spam controls tightened

Last week both Sheeri and Mark Callaghan pointed my attention to the fact that if they comment on articles on this blog, they end up getting lot of email spam that is sent via OpenLife.cc. Thank you for informing me, I was completely unaware that this was still happening. The problem should now be fixed - you should not get any more spam mail, whether related to your old comments on this site or any new ones I hope you will still make.

When spam bots figured out how to spam Drupal based blogs - including working around the Captcha - I enabled the Drupal Antispam module which uses the Akismet service to check all incoming comments for spam. It has worked very well. On average AntiSpam blocks 40 spam comments a day, and the accuracy is very good (see stats below).

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Hand holding PostgreSQL on a simple query

With MySQL it was for a long time the case that a lot of sub queries would actually perform poorly, because of poor execution plans. (This is no longer the case in MariaDB 5.5 or the upcoming MySQL 5.6.) Because of this, any MySQL DBA knows the rule of thumb that sub-queries should basically be avoided and you can usually get the same result by using JOINs instead.

I've now learned why PostgreSQL DBAs like sub queries so much. PostgreSQL - being the most advanced open source database - apparently does the exact opposite optimizations as MySQL: it requires you to rewrite simple queries into complex subqueries to get what you want. (Update: Mark Callaghan points out that MySQL - while it does create indexes automatically for foreign keys - actually has the same problems with the query plan as Postgres has in this post. See comments for details.)

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MySQL and PostgreSQL faces at Froscon

My three previous blog posts I already wrote from Froscon. In this post I still want to go back and mention some people I met and discussions I had.

The MySQL side

There were of course many MySQL people, with both SkySQL and Oracle sponsoring. It was great to meet Carsten from Oracle, who has joined the MySQL Sales Engineer team in Europe (he moved from an OpenOffice position). That's my former team, so it was great to see a new face!

Going there the person I was most looking forward to meet was Hana Hütter, formerly a MySQL account manager for Central Europe, and now doing the same at SkySQL. My first ever MySQL sales gig was with Hana, and Ralf Gebhart who is also now with SkySQL but was not at Froscon. While Ralf was there only that first time to teach me how to be a Sales Engineer, with Hana we then continued to sell MySQL into telecom companies in many European cities. I had not met Hana since I left Sun. It was really great to see again. We had lunch, I told about my experiments with Galera and she told about her customers being interested in it too. It was great to get in touch with the "frontlines" again!

She also told me a great story about MySQL adoption in Europe...

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Understanding the Galera commit sequence and innodb_doublewrite_buffer back to 1

People often assume the reason I talk at conferences is because I like to teach them about Galera, MySQL and other cool, open source things. That's of course true to some extent. But for me personally, another reason is even more important: It happens almost always that the audience teaches me something. Thus the process of public speaking has increasingly become my way to learn new insights. Low level details that aren't easy to learn by just RTFM.

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Froscon: How big corporations play the open source game

Here are the slides of the talk I just gave at Froscon. (Video should be available soon.)


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State of the MySQL forks - conclusions

I promised to still post some general comments about the MySQL ecosystem, to conclude my outlook of State of the MySQL forks and Drizzle. I will do this now in the form of answering questions I got in the comments, twitter and some that I make up just myself.

Oracle has not stopped updating bzr trees

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But what about Drizzle?

I got several comments and questions on my previous blog "The State of the MySQL forks". One question was "Why didn't you mention Drizzle?" So I will say something about Drizzle here before concluding with other remarks.

So why didn't you mention Drizzle?

Mainly because the post was already long and also I had to wrap up and call into a meeting.

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