David Goodwin

Our work server seems to enjoy crashing (at the moment) about once a day – but when I go to look at the console I can’t see anything because the screen has dimmed to black – and as the computer has locked up, I can’t wake the screen up to see if there is a useful kernel panic message.

It turns out my answer lies with /etc/console-tools/config – as this is Debian Squeeze.

See http://serverfault.com/questions/137728/how-do-i-permanently-disable-linuxs-console-screen-saver-system-wide

Next up, I just needed to stop it from dimming the console font – adding this to /etc/rc.local seems to help :

setterm -half-bright off

I’ve written the below Python script to defragment MySQL database tables. This should work with both InnoDB and MyISAM table formats, and is just calling “OPTIMIZE TABLE blah.foo”. It rummages through the information_schema for tables which may be defragmented.

You should be able to run it on any Debian based system without making any alterations.

#!/usr/bin/env python
import ConfigParser
import os
import time

# On Debian, /etc/mysql/debian.cnf contains 'root' a like login and password.
config = ConfigParser.ConfigParser()
config.read("/etc/mysql/debian.cnf")
username = config.get('client', 'user')
password = config.get('client', 'password')
hostname = config.get('client', 'host')

defragmented_tables_cmd="mysql -u %s -p%s -h %s --skip-column-names --batch  -e 'SELECT TABLE_SCHEMA, TABLE_NAME, Data_free FROM information_schema.TABLES WHERE Data_free > 1000'" % (username, password, hostname)

# This will explode if any databases or tables have spaces in their names.
for dbtable in os.popen(defragmented_tables_cmd).readlines():
    (database,table,space_free) = dbtable.split(None)
    print " Defragmenting database : %s, table: %s, space free: %s " % (database, table, space_free)
    os.popen("mysql --batch -u %s -p%s -h %s -e 'OPTIMIZE TABLE %s' " % (username, password, hostname, database + '.' + table))

Having written this, I don’t think it does any more than “mysqloptimize –all-databases”, althoug you could make the above run selectively (i.e. only on certain databases / table formats / disk free amounts ).

My son woke up at 6am crying quite loudly this morning – he’d been having a nightmare involving a Chocolate Headed Pirate being mean and nasty to him.

Personally I think a chocolate headed pirate would be quite tasty – although perhaps it’d be a bit more than I could eat in one sitting (or one week),  however, just like I don’t really understand his fear of Mr Choco Pirate, I’m sure there are many things I’m afraid of which he’d find funny.

Oh, the joys of childhood!

I’m currently refactoring some legacy third party PHP code, and as the old saying goes, the real metric is WTFs per minute.

So, just to entertain any readers, how about :

1. Writing pagination links for a search form, but if there are more than 20 pages of results, add 20 onto whatever the maximum number of pages there are – so you get 20 invalid links at the end of the pagination list (clicking on them will show no results). I guess it looks like there are lots of results at least.
2. if(isset($_GET[‘foo’]) == 0) … (wouldn’t if(!isset($_GET[‘foo’]) be easier to read?).
3. Presumably not knowing what a while(…) { … } loop is, and always using something like: $row = mysql_fetch_assoc($x); do { … } while ($row = mysql_fetch_assoc($x)) ….
4. Always including mysql_free_result($foo) after every query…. why bother?
5. Always having an //END IF comment, even if the if(..) { } statement is only 3 lines long.
6. The write_out_the_header() function which consists of a switch statement nearly 2900 lines long, which is just responsible for setting things like the <title> and some meta tags for every page in the site.
7. When doing results pagination, for even numbered page links, write out the ‘jump’ URL differently (starting with a &, instead of a ?). Some numbers are more even/equal than others…. I guess.
8. Executing a separate query each time within a loop rather than doing a simple join to start with….