Xaprb

I wrote a while ago about how mext works — it runs “mysqladmin extended-status” and formats it nicely. But what if you want to use it to format saved output that you’ve put into a file? It’s actually very easy. You can tell it what command-line to run to generate its input. By default you are probably going to tell it to run “mysqladmin ext -ri10″ or something like that, but you can just as easily make it run “cat my-saved-output”.

Let’s see how this can be useful. Imagine I have a server that stalls every now and then, and I’ve set up mk-loadavg to watch for this and capture information about system activity with a script that contains

$ mysqladmin ext -c 30 -i1 > mysqladmin-output.txt

That’ll gather 30 samples one second apart. Now I’ll format it:

$ wget -q http://www.maatkit.org/mext
$ sh mext -r -- cat mysqladmin-output.txt | less -S

I’m piping the output into less -S so that I can see unwrapped output. 30 samples of mysql status variables are going to be aligned in columns next to each other, so without the -S flag I’ll probably see something unhelpful.

If you have a hard time visualizing the above, go ahead and run the commands! It’ll take only a minute, and it’ll make a lot more sense to you then. This is a really useful way to summarize and understand what is going on (or has gone on) inside your MySQL server.

I tweaked the mext script so it auto-detects the necessary column widths for each sample.

I always say that the ultimate MySQL tuning script is an expert human. To that end, I generally try to build tools that help a human be more productive with the raw information from MySQL. One of the things we look at during a performance audit is the MySQL status counters. It’s useful to look at a) absolute values and b) several incremental snapshots. I’ve written a small shell script called “mext” that can make this a little easier.

It looks like this:

baron@kanga:~$ mext -- mysqladmin ext -ri1 -c3
Aborted_clients                               1      0      0
Aborted_connects                              0      0      0
Binlog_cache_disk_use                         0      0      0
Binlog_cache_use                              0      0      0
Bytes_received                             1167     35     35
Bytes_sent                                38926   6337   6337
....

This isn’t an original idea. Ryan Lowe made a Perl version of this first. I used his version for a while, but after working on a few machines that didn’t have the necessary Perl libraries (maybe one of them didn’t even have Perl, I forget) I decided to do it in shell.

There’s an added feature. It’ll do incremental/differential/relative output for you. The mysqladmin that ships with MySQL 5.1 has a bug that stops it from iterating with -r. So the script I wrote can accept a -r option, which can then be left off the arguments to mysqladmin:

baron@kanga:~$ mext -r -- mysqladmin ext -i1 -c3

It’s kind of a generic tool that you could use with other things besides mysqladmin, but it’s also kind of tweaked for that purpose. You can get mext here.