Recently I had a case with a web server farm where a random node went down every few minutes. I don't mean any of them rebooted except once or twice, but rather they were slowing down so much that practically stopped serving any requests and were being pulled out from the LVS cluster. The traffic was not any different than usual, all other elements of the system worked perfectly fine (e.g. databases, storage), no one started any backup in the middle of the day as it happens sometimes... so what was happening?

First I am going to describe the setup a little bit. As I already mentioned it was about web servers. Each of them was running Lighttpd that handled the requests coming from the internet. It was configured however only to serve static content, such as images. The requests asking for PHP files were passed down with proxy module to Apache listening on another TCP port.

And so I started investigating the problem. As it turned out …

Just a short blog entry about a funny error message I’ve got while trying to activate a physical standby database: SQL> alter database recover managed standby database finish skip standby logfile; alter database recover managed standby database finish skip standby logfile * ERROR at line 1: ORA-00283: recovery session canceled due to errors ORA-01110: data file 1: '/oradata/stage/datafile/system_01.dbf' ORA-01122: database file 1 [...]

Again I have a well neglected and documented feature of MySQL. As we all often need and use locks in MySQL, we tend to forget (or not bother about) MySQL internals and how they cause trouble. For example, try something like LOCK TABLE ... WRITE on an InnoDB table in a transaction and see the same transaction getting timed out while waiting for a lock on one of the rows, Ref: [Bug 5998]. All these problems occur when we have difference in semantics of statement at MySQL and Engine levels. But recently, we figured out this good technique of keeping the logic with ourselves and not relying on MySQL too much. Though even this technique is not fool proof in all the cases.

The secret is: use GET_LOCK function of MySQL. GET_LOCK(str, timeout) function tries to get an exclusive lock with a name (str) using timeout seconds. The return values are tri-state, …

I had many problems with the wordpress hosting, I must admit that most of them come from the fact that I don’t want to pay… Anyway, Ronald Bradford, a colleague at MySQL, offered me to host my blog on a server he manages so I switched. Now I can edit my style sheet and upload files, this should helps a lot.

Thanks a lot Ronald!

Yves

My RSS reader just spit out an article on Google creating its own switches:
http://www.nyquistcapital.com/2007/11/16/googles-secret-10gbe-switch/

I've been hearing rumors about this for a while, and I am left completed unsurprised by it. From hacking with the Linksys WRTG-54 for the last couple of years I have realized that I wanted to do something similar. While I have a nice HP switch that I am using, it pales in comparison feature wise to what I have in the DD-WRT units that I use. I would like to replace the HP switch with a new switch running DD-WRT but I do not see that happening anytime soon. Trying to get 48 ports into a single piece of commodity hardware just does not seem to be viable. No one builds the hardware, and I am not interested in doing this with multiple computers. To make it really interesting for me, I …

Just in time of the holidays, Solid has released solidDB for MySQL 5.1 Beta. This release implements the solidDB storage engine as a dynamically loading plugin. Check it out at http://dev.soliddb.com/download

Happy Holiday Hacking!

I started this as a response to Keith Murphy’s post at http://www.paragon-cs.com/wordpress/?p=54, but it got long, so it deserves its own post. The basic context is figuring out how not to cause duplicate information if a large INSERT statement fails before finishing.

Firstly, the surefire way to make sure there are no duplicates if you have a unique (or primary) key is to use INSERT IGNORE INTO.

Secondly, I just experimented with adding an index to an InnoDB table that had 1 million rows, and here’s what I got (please note, this is one experience only, the plural of “anecdote” is *not* “data”; also I did this in this particular order, so there may have been caching taking place):

Way #1:
- ALTER the table to add the new index. This was the slowest method, taking over 13 minutes.

Way #2:
- CREATE a new table with …

I started this as a response to Keith Murphy’s post at http://www.paragon-cs.com/wordpress/?p=54, but it got long, so it deserves its own post. The basic context is figuring out how not to cause duplicate information if a large INSERT statement fails before finishing.
Firstly, the surefire way to make sure there are no duplicates if you have a unique (or primary) key is to use INSERT IGNORE INTO.
Secondly, I just experimented with adding an index to an InnoDB table that had 1 million rows, and here’s what I got (please note, this is one experience only, the plural of “anecdote” is *not* “data”; also I did this in this particular order, so there may have been caching taking place):  More »

IDG LinuxWorld has done an article about the training for MySQL that Open Query offers. It's called Database training now an Open Query.

Cool - well, of course I'd say that, I don't think that you should feel it's cool too ;-) but such press coverage is always good for a young company. Getting the word out further.

As most of you probably know now, Workbench supports two visualization modes: hardware & software based. Unfortunately automatic switcher was not in place by the time when beta version came out (will be fixed in a week), so some of you, who don’t have video subsystem supporting OpenGL v1.5, will encounter error on start when trying to run hardware based configuration. Note v1.5 is a minimum required version of OpenGL needed to start Workbench. You can get detailed information about your video subsystem using one of these tools: OpenGL-Extension-Viewer or GPU-Caps-Viewer. Both of them support export into xml file, so you can also easily attach your video configuration to your bug report when needed.