Have you ever wanted to play around with(test ;) MySQL replication/clustering techniques, LVS/Apache load balancing etc but didn't have the hardware available and where smart enough not to use a production environment?

Well an easy way to be able to do this is by creating a sandbox environment using something like qemu, xen, vmware or UML which allow you to create virtual machines running inside a protected environment on your own desktop machine or whatever hardware you have spare, just be sure you have enough memory. This article will cover setting up a sandbox using UML.

My GNU distro of choice is Archlinux and this article will be based around it, but you should be able to take the …

Had a customer issue come through right before I left for the day. Hadn’t seen this happen before and google was not too helpful.

Problem: We had the tmp-dir set as /var/tmp which was on it’s own partition of 5GB. This is a relatively small database of about 15GB. Customer has some replication slaves setup and was running a LOAD DATA INFILE on the master. File was about 12GB, so the slave creates a SQL-DATA-1024-512.data file in the tmp directory to buffer that INFILE command coming from the master. Well, eventually that filled up the /var/tmp partition.

Solution: stop the server, change the tmp-dir=/bigger-partition, move the file to the new tmp location, restart cluster, all good.

Prevention: Make sure your tmp-dir setting is on a large enough partition to hold your temporary files, and make sure if you’re going to load a data file on the master that’s bigger …

This release contains bug fixes and new features. It also contains a new tool: my implementation of Paul Tuckfield's relay log pipelining idea. I have had quite a few responses to that blog post, and requests for the code. So I'm releasing it as part of Maatkit.

I dashed off a hasty post about speeding up replication slaves, and gave no references or explanation. That's what happens when I write quickly! This post explains what the heck I was talking about.

Paul Tuckfield of YouTube has spoken about how he sped up his slaves by pre-fetching the slave's relay logs. I wrote an implementation of this, tried it on my workload, and it didn't speed them up. (I didn't expect it to; I don't have the right workload). I had a few email exchanges with Paul and some other experts on the topic and we agreed my workload isn't going to benefit from the pre-fetching.

In the meantime, I've got a pretty sophisticated implementation of Paul's idea just sitting around, unused. I haven't released it for the same reasons Paul didn't release his: I'm afraid it might do more harm than good.

However, if you'd like the code, send me an email at [baron at this domain] and I'll share the code with you. In return, I would like you to tell me about your hardware and your workload, and to do at least some rudimentary benchmarks to show whether it works or not on your workload. If I find that this is beneficial for …

Whew! I just finished a marathon of revisions. It's been a while since I posted about our progress, so here's an update for the curious readers.

There is a lot of information out there about how to setup circular replication but nothing about how to recover it when all else fails. This article will cover a quick and easy method I use. Depending on the size of your database and the interconnects between servers this method may not be suitable due to the need to copy all replicated databases from one good server to all other servers in the replication circle which requires a certain amount of down time respectively.

OK, so one server or more is showing Slave_IO_Running and/or Slave_SQL_Running as No and there is some error about a failed query when you run "show slave status;" and no amount of effort to fix it is working. First DO NOT PANIC. It is broken, OK, tell yourself that and realise that trying to fix something when you are in a panicked state is only liable to make the situation worse, hell I'd guarantee it, so …

This release contains bug fixes and new features. Click through to the full article for the details. I'll also write more about the changes in a separate article.

My posts lately have been mostly progress reports and release notices. That's because we're in the home stretch on the book, and I don't have much spare time. However, a lot has also been changing with Maatkit, and I wanted to take some time to write about it properly.

... I didn't get two-way sync done, and I didn't get the Nibble algorithm done. That much I expected. But I also didn't get the current work released tonight because I'm paranoid about breaking things. I'm trying to go through all the tools and write at least a basic test for them to be sure they can do the simplest "unit of work" (such as mk-find running and printing out that it finds the mysql.columns_priv table).

It's good that I'm doing this. I found that mk-heartbeat suddenly doesn't work on my Ubuntu 7.10 laptop. It goes into infinite sleep. Can anyone repro this and/or diagnose? The same code works fine on my Gentoo servers at work.

Hopefully I'll be able to release something very soon. Release early/often is fine, but "knowingly release brokenness" isn't in my code of conduct :)