Peterbe.com

For the impatient: Jed and Wing IDE are programming editors I use for my Python, Javascript, HTML, CSS editing. One is ultra-light, fast and simple. The other one is very feature full, commercial and slow (in comparison to Jed).

I've been using Jed now for several years on Linux. It's an "Emacs clone" ¹ in that almost the same key bindings you have in Emacs work in Jed. A few weeks ago I started using Wing IDE 3.1 instead to see if I could learn to love it. I got a professional license as a gift for participating in the PyCon 2008 sprint by Wingware (the company behind Wing IDE). As of yesterday I've gone back to Jed but I haven't uninstalled Wing yet. Here are what I've learned from using both quite a bit. Note, I'm not comparing things that they both do equally well such as macros, community support and block indentation.

I have a Thinkpad T60p which is working really well for me. On it I've run various flavors of Ubuntu and as of a couple of weeks ago I put on Ubuntu 8.10 which has been working very well too except that I didn't get any options in the Preferences menu to switch off the damn loud system beep. The beep comes through the speakers and at a much much louder volume than any other sound or music.

I tried changing thins in BIOS and I tried installing various packages hoping one of them will give me the options. Finally I've found out how to disable it:

$ sudo modprobe -r pcspkr

This tip page showed me how to put it into /etc so it's applied all the time. Thanks Andy!

...over PostgreSQL? I've just read through this document:MySQL vs PostgreSQL and it's obvious paragraph after paragraph that PostgreSQL is the better database. Performance, features and community are all in PostgreSQL's favor. There is almost nothing in MySQL's favor apart from obscure things like faster count(*) (without conditionals) and built in replication support. In the last two weeks I've also had the great fortune of playing with full textindexing in both MySQL and PostgreSQL and again, MySQL sucks ass and PostgreSQL (8.3) is really impressive and fast. (I've used both databases quite extensively over the past 8 years as a web developer)

I once heard that Google uses MySQL for its user database with a custom built transaction machine. And I read that Google engineers had donated some great code to the MySQL project. But why do they bother? What do they know that other engineers don't? And why is MySQL so popular with cheap stack-em-high LAMP hosting sites?

I do understand that PostgreSQL came off a bad start 5 years ago(ish) when it didn't support Windows which meant that newbies had to use MySQL and that stigma is still lingering but that was a very long time ago.

I guess it takes a lot of convincing to switch from one technology to another once you've set your mind on something. That's why we're human. A proof of this is shown if you scroll down to the bottom of this page there's a little simple survey and despite being on a long article with objective convincing arguments that PostgreSQL is better MySQL is doing quite well. Why?

I'm talking about Squid the web proxy cache server and Calamaris the Squid log file analyzer not food. Calamaris was a breeze to set up and now it emails me once a month a report summary of what Squid has done for my site each month. It's brilliant because it includes a piece of information that both really easy to understand and really useful no matter how technical you are:

Proxy statistics                                                                
-------------------------------------------------------------------- 
Average speed increase:                                     %  44.57 

Nota bena: I've had to work on this. It used to be a lot lower before but I've worked on setting no-refresh on selected few resources and I've tweaked the Cache-Control headers here and there.

What people sometimes forget about Squid is that it can actually slow down your site too. On an individual object that you test with ab you can go from 50 requests/sec to 2000 requests/sec but for large sites with many many objects Squid has to do a lot of thinking to work out what to cache, not to cache, put in RAM, etc. Just installing Squid is not necessarily good enough. You have to massage and caress it till it starts to work for you. And to get to that Calamaris really helps.

Today I moved a bunch of sites over from Apache to Nginx but still keeping Squid in between as a http accelerator (I hope to replace Squid with Varnish soon). I did a quick benchmark of a HTML page that is cached by Squid, 4 times via Apache and 4 times via Nginx. The results:

Apache2
********
Requests per second:    1601.34 [#/sec] (mean)
Time per request:       6.268 [ms] (mean)
Time per request:       0.627 [ms] (mean, across all concurrent requests)
Transfer rate:          13020.50 [Kbytes/sec] received

Nginx
********
Requests per second:    1810.02 [#/sec] (mean)
Time per request:       5.6435 [ms] (mean)
Time per request:       0.5645 [ms] (mean, across all concurrent requests)
Transfer rate:          14591.35 [Kbytes/sec] received

That's "only" 13% faster and I had hoped for a bigger difference but the test is very simple and depends on how Squid feels. The other important test would be to see how much less CPU and memory Nginx uses during the stresstest period but that's for another day.

One note: This is Nginx 0.4.3 on Debian Etch. The current stable release is Nginx 0.6.13. I'll need to talk to my sys admins to remedy this. Perhaps it makes a difference on the benchmark, I don't know.

I often need to know the path to a file so that I can put that in an email for example. The only way I know is to copy and paste the output of pwd followed by a slash / followed by the name of the file. This is too much work so I wrote a quick bash script to combine this into one. Now I can do this:

$ cd bin
$ pwdf todo.sh 
/home/peterbe/bin/todo.sh

I call it pwdf since it's pwd + file. Here's the code for the curious:

#!/bin/bash
echo -n `pwd`
echo -n '/'
echo $1

Is there no easier way built in into Linux already?

First of all, I understand that the problem cron solves is a hard one but come on, it's been many years now without much progress. At least not in the usability field of cron jobs. Secondly, I don't know of an operating system that does this better. Perhaps there is one. All I'm saying here is that this aspect of Linux sucks. The issues I have with cron are:

Beef number 1 Is it root, user1 or user2 running a crontab job? I'll have to su into each suspected user and run crontab -l. Granted, some jobs require root access and others don't but it nevertheless makes it hard to find the configured jobs when maintaining someones server.

Beef number 2 Even though they do such a similar thing, it feels like /etc/cron.* is a different battlefield from crontab. Why can't this all be in one coherent place?

Beef number 3 The crontab syntax. How difficult would it be to allow an interface to accept user input as "every 10 minutes" or "01.30 every day"?

Beef number 4 With there being 12 different ways (sarcasm) to write cron job scripts there's no coherent place to collect all log and errors that happen from cron. Couldn't it be default to always write to /var/log/cron/access.log and all executions that cause a write to stderr could append to /var/log/cron/error.log

I don't think Anacron would make me any happier since the problem Anacron solves was not one of the problems I listed above. And lastly, I wouldn't be surprised if there's a semi-abandoned Open Source project on SourceForge that is user friendly but what I'm after is something to get into stock Linux. Kind of like apt/aptitude/dselect is for dpkg maybe?

My colleague Jan showed me how to do this so I'm going to blog about it to not forget and perhaps by being here other people might be able to search and find the solution too. I installed nginx because I wanted to play with it as an alternative to apache on my laptop. Now I've played enough and I'm going to want to remove it. My first attempt didn't work:

peterbe@trillian:~ $ sudo apt-get --purge remove nginx
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
 nginx*
0 upgraded, 0 newly installed, 1 to remove and 116 not upgraded.
1 not fully installed or removed.
Need to get 0B of archives.
After unpacking 528kB disk space will be freed.
Do you want to continue [Y/n]?
(Reading database ... 242827 files and directories currently installed.)
Removing nginx ...
Stopping nginx: invoke-rc.d: initscript nginx, action "stop" failed.
dpkg: error processing nginx (--purge):
 subprocess pre-removal script returned error exit status 1
Starting nginx: invoke-rc.d: initscript nginx, action "start" failed.
dpkg: error while cleaning up:
 subprocess post-installation script returned error exit status 1
Errors were encountered while processing:
 nginx
E: Sub-process /usr/bin/dpkg returned an error code (1)

I tried this both before and after having stopped and started nginx. Nothing worked. The trick is to fiddle with the init script /etc/init.d/nginx and insert a exit 0 at the top so that it now starts like this:

#!/bin/sh
exit 0

Once saved and you try apt-get --purge remove nginx it will work. It might warn you that /var/log/nginx aren't removed because they're not empty but you can safely remove them manually unless you want to keep them.

Because I always forget, here's how to check if a file exists before attempting to delete it in bash:

[ -f foobar.html ] && rm foobar.html

If you don't do it this way and the file doesn't exist you get this:

rm: cannot remove `foobar.html': No such file or directory

I've never really needed it but I've been looking for a tool that is super easy to use that quickly looks up the location of an IP address. The super easy tool is called hostip.info and this is what happens when you do a lookup on www.peterbe.com's IP at http://api.hostip.info/get_html.php?ip=80.68.212.7 :

Country: UNITED KINGDOM (UK)
City: (Unknown city)

Cool. I'll remember that till next I really need this. I discovered hostip.info by reading this cool blog by Corey Goldberg