One common theme in the questions our MySQL Support customers ask is Replication Lag. The story is typically along the lines everything is same as before and for some unknown reason the slave is started to lag and not catching up any more. I always smile at “nothing has changed” claim as it usually wrong, and one should claim I’m not aware of any change. Digging deeper we would find some change, though often subtle as computers are state machines and with no external and internal changes they behave the same way.
Codership team announced availability of MySQL/Galera 0.8.1, which is minor release, but actually it has bunch of improvements that makes Galera replication more user friendly (there are many bugs fixed, reported by me personally, what annoyed me a lot).
As part of my evaluation activity I ported MySQL/Galera 0.8.1 to Percona Server/Galera 0.8.1 and you can get source code on Launchpad.
href="http://d1wcmuriwzc7sn.cloudfront.net/wp-content/uploads/2011/07/scale-graph.png"> class="alignleft size-full wp-image-1418" title="scale graph" src="http://d1wcmuriwzc7sn.cloudfront.net/wp-content/uploads/2011/07/scale-graph.png" alt="" width="222" height="240" />There are a lot of scalability challenges we see with clients over and over. The list could easily include 20, 50 or even 100 items, but we shortened it down to the biggest five issues we see.
1. Tune those queries
Even though multiple fixes have been implemented in Percona Server and MySQL 5.5, there are still workloads in which case mutex (or rw-lock) contention is a performance limiting factor, helped by ever growing number of cores available in the systems. It is interesting though the contention may manifest itself in the different form from the system monitoring standpoint. In many cases as heavy contention happens user CPU will be very high, and the context switches will be somewhere reasonable.
I recently set up the solarized color theme for my terminal emulator. I’ve been meaning to do this for a while, but procrastinated. However, I finally got really frustrated with the colors I get from “ls” sometimes — I use a dark terminal with light fonts, and the directory listings in particular can become invisible, with dark blue on black.
How would you check whether some TIMESTAMP column falls within a given day, say July 26th, 2011?
This is a question I tend to ask students, and usually I get the same range of answers. Some are wrong; some cannot utilize an index, some are correct, and some are temporarily correct. I wish to take a closer look at the last. Such an answer looks like this:
I got a serendipitous call (thanks!) yesterday asking what would be needed to tune a database for better performance. It is a question that I hear often, but I never thought about answering it in public. Here’s a consolidated version of what I explained during our conversation.
Congratulations and thanks to Monty Program on the release of MariaDB 5.3! This looks like a great release. (I haven’t had a chance to try it yet.) I really welcome the query optimizer improvements; the list of changes is huge. There are a lot of fixes for problems I’ve seen for years. And there’s group commit, and high-resolution date/time types, and lots more.
The OpenWorld early bird pricing ends this Friday, July 29!
This is the last week to use the “MYSQL11″ special MySQL discount code
and get $1,000 over regular price, so please take time to share the code
again with customers/prospects or remind them to register by Friday.