Tuesday, July 31, 2007

Google Reader Bug report - use Atom <id/> elements

I am directly subscribed to Sam Ruby's feed. I recently added Planet Intertwingly as well, which contains Sam's blog. Both feeds are served as application/atom+xml. In Google Reader, duplicate items show up (for Sam, Steve Loughran, and others that overlap from my other subscriptions. I don't want to remove individual subscriptions in case Sam removes them from Planet Intertwingly.

From my readings of the spec a while ago, that was an explicit rationale for having id's associated with each entry. As you would expect, the id's are the same. From Planet Intertwingly:

<link href="http://intertwingly.net/blog/2007/07/31/Agile-Financial-Publishing" rel="alternate" type="text/html"/>
<link href="http://intertwingly.net/blog/2619.atom" rel="replies" type="text/html"/>
<title>Agile Financial Publishing</title>

From Intertwingly:

<link href="2007/07/31/Agile-Financial-Publishing"/>
<link rel="replies" href="2619.atom" thr:count="1" thr:updated="2007-07-31T12:15:28-04:00"/>
<title>Agile Financial Publishing</title>

Those atom:id element IRIs appear to be the same to me...

Wednesday, July 25, 2007

Objective review of why Vista pisses me off (or Why isn't Vista more like Ubuntu?

So I'm being completely upfront in the title as to where I am on this one, but I think that it's worth giving some airtime to a few of these. Readers might care to note that they should route around the "grumpy Yorkshireman that doesn't like change" for some of these. You never know, I might get some comments explaining why I'm a bozo when it comes to Windows.

Avalon and the new Windows Aero UI.
I gave it two weeks and then I'd had enough. Does it really make me more productive having all that shit, or is it just effects for the sake of it? I have the same opinion on Compiz - I haven't yet seen a compelling reason for it to exist, beyond being secretly sponsored by Nvidia / ATI to make people get shiny new graphics cards. Let the conspiracy theorists chew on that one. And despite paying Dell more for a fancy graphics card in this laptop,


apparently it's not that good.

Blue screen of Death
No really, I had one in my first week, and I've had one since then. Lovely. Occasionally (once a quarter?) when running Ubuntu Dapper, I've had X lock up on me and be completely unresponsive, to the extent that I couldn't even switch to a virtual terminal or ssh into the box and do something to it. The first time this happened, I went climbing at lunchtime, came back and it was still borked, so just a hard reboot to fix that. A reboot once a quarter on a development machine doesn't strike me as too bad. Vista is managing once a week at the moment, and in neither case am I writing C or any system level code. It's all Java / Python / Ruby and that sort of level.

Black screen of death
That was a Vista new feature for me; I've never had that on previous versions of Windows. This is progress people!

Still no decent shell
I'm using Cygwin, but it doesn't seem to let me tail files and press Return to get some space in between lines. Minor, but annoying.

Continual swapping
Previously I was on a 2GB RAM Dell workstation, and now I have a 2GB RAM Dell laptop. The laptop is always swapping. What's changed? Well, I'm now on Vista rather than Ubuntu and I'm not running Oracle XE anymore, but otherwise the services running are much the same. IDEA / Eclipse, Tomcat, MySQL, Firefox, intermittent email client and a text editor. Don't know why Vista is always swapping (TaskMngr thinks it has 700MB free) but it's bloody annoying.

Broken file permissions
Doing a release today, the VPN crashed (don't know if that was Vista, BT, the Windows 2003 Server or something else. That appears to have left me with the following undeletable file.


So Vista has let me create a file that I don't have the rights to delete. That's smashing!


Random security policies
Or that's what I'm guessing is causing this anyway. If so, then a learning mode like AppArmor has would be nice. See



No, when I ask for a large amount of heap to be allocated for my Java process, I don't really know what I'm doing, so please stop me. Thank you Vista, you're my hero.

Update: LazyWeb to the rescue, at least about the disk thrashing issue.

Tuesday, July 24, 2007

The Hustler

There was a bag of sweets up on the kitchen top. Connor spotted these and was after them, but I told him "Not for breakfast". After I'd gone to work, he asked Al the same and got the same response. His reaction?

OK Mummy, me just hold it, OK?

OK Connor.

(Al continues ironing. Some time passes)

Connor: (Coming back into the kitchen)
Look Mummy, me just hold it, OK?

Well done Connor.

(More time passes)

Connor: (Comes back into the kitchen again)
Look Mummy, me still hold it

Good boy, Connor!

After an hour, the ironing is done and Al's about to phone me to say how well-disciplined the boy's been, just holding the sweets. So she takes the ironing upstairs and comes back down to see Connor doing his Muttley laugh and just shy of shovelling all of the sweets into his mouth! Gamed by a 2 year old.

Friday, July 20, 2007

Good ETag support requires thinking about it up-front

I posted a comment on this but I thought it worthwhile going a little deeper.

Blogger doesn't support Trackback so I'll just post and link.

My point was not to argue about how little code is required to implement sending an ETag and checking an ETag based on the MD5 hash of your content (that's pretty much a library issue which should level out to be equal over time) but to go a little deeper into ETags.

I've been reading Sam Ruby long enough to have had the benefit of ETags drummed into me. The posts that Bill links to are focused on the network savings aspect of conditional GET. But you can also save server processing power, if you put a little more thought into your application model.

So we come back to the requirements for Java frameworks to support ETags such that it is possible to avoid doing the bulk of the server side processing. Caveat this could well be premature optimization, and is merely me thinking out loud. Struts is the one I'm most familiar with and I think with the struts-chain RequestProcessor, this approach could be used, but anything that works as a chain would do for this (so pure Filters would also work).

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterChain) throws IOException, ServletException {

HttpServletRequest httpRequest = (HttpServletRequest) request;

* Do something that works out what is required to render a response
* for this request and generate an ETag based on that. So here we
* have moved away from the approach of generating ETags from MD5
* hashes of the response body.
ETag currentResourceETag = calculateETag(httpRequest);
ETag incomingETag = extractETag(httpRequest);

if (currentResourceETag.equals(incomingETag)) {
} else {
filterChain.doFilter(request, response);
response.addHeader("Etag", currentResourceETag.stringValue());


You would need to be able to obtain the items responsible for determining the ETag value reasonably early in the request processing, before any really expensive operations. Not sure what implications that has for the layers in your application, or if you were using strict MVC how disruptive / worthwhile it would be to try this approach...

Wednesday, July 18, 2007

Jython - UnicodeData mirrored is complete!

from test_support import verify, verbose
import sha

encoding = 'utf-8'

def test_mirrored():

h = sha.sha()

for i in range(65536):
c = unichr(i)
print "%i : %i%c" % (i, unicodedata.mirrored(c), unichr(10)),

# Value returned by Python 2.5, which uses Unicode 4.2
#verify('91cd30c6c81911835dbcbed083f99fc9fc073e4a' == h.hexdigest(),
# h.hexdigest())

# Value returned by current Jython implementation, which uses Unicode 5.0
verify('595795a212ca0ac629d6b2dfb09c703a472adb03' == h.hexdigest(),

# Add next test!

if __name__ == '__main__':
import unicodedata

OK, it's only for the BMP, but it's a good start. Supporting supplementary characters (in Java terminology) or the other sixteeen planes would need a more fundamental change to PyUnicode, methinks. Now I need to start adding the other unicodedata methods which should be fairly straightforward. Then I'll have a working implementation to post to the dev list. Maybe end of this month, unless Baby comes and I lose my late night hacking time?

Jython UnicodeData mirroring

for i in range(65536):
c = unichr(i)
print "%i : %i%c" % (i, unicodedata.mirrored(c), unichr(10)) ,

jabley@miq-jabley ~/work/eclipse/workspaces/personal/jython-trunk/jython
$ diff jython-mirrored.txt python-mirrored.txt
< 10176 : 0
> 10176 : 1
< 10179 : 0
< 10180 : 0
< 10181 : 0
< 10182 : 0
> 10179 : 1
> 10180 : 1
> 10181 : 1
> 10182 : 1
< 11778 : 0
< 11779 : 0
< 11780 : 0
< 11781 : 0
> 11778 : 1
> 11779 : 1
> 11780 : 1
> 11781 : 1
< 11785 : 0
< 11786 : 0
> 11785 : 1
> 11786 : 1
< 11788 : 0
< 11789 : 0
> 11788 : 1
> 11789 : 1
< 11804 : 0
< 11805 : 0
> 11804 : 1
> 11805 : 1

I was hoping to use java.lang.Character.isMirrored(char), but the above is the result of diffing the output for jython and python running my test and diff-ing the output. Looking in more detail, Java 1.4 supports UCD 3.2, then Java 5 and Java 6 both only have support for UCD 4.0.

jabley@miq-jabley ~/work/eclipse/workspaces/personal/jython-trunk/jython
$ python
Python 2.5.1 (r251:54863, May 18 2007, 16:56:43)
[GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import unicodedata
>>> unicodedata.unidata_version

And I'm getting the sneaking feeling that I've done something like that before, but it's been so long since I did any development in this area that I've forgotten it!

Friday, July 13, 2007

The Graduate

The Bash had his nursery graduation a couple of weeks ago (must put the photos up on Flickr) and then his last day in nursery was yesterday. He didn't seem too bothered; more excited about going on holiday and spending the summer with Al. But that 4 years has gone by fast!

Sunday, July 08, 2007

Our little philosopher

Callum, we don't need to take your toys into Legoland since there's enough things in there to keep you busy. How does playing with your toys make you feel versus going on a ride?


So what's a ride like then...like playing with toys.

So Daddy, when you're on the ride, it's like the ride is playing with you. You're the toy!

Me (slightly shocked)
Yes, that's right Callum. Good analogy.

So Callum, your homework is to write an essay on the inside of a brick.

Silly Daddy, that's just pretend!

He's sharp, that one.