The good news is that all is good on Afrigator now. All blogs that are using some form of Pubsubhubbub service will be realtime in no time.

If you’re running on WordPress (not WordPress.com) and you have not yet installed PuSHPress, please do so soon!

Go is not a scripting (a.k.a. interpreted) language, but a compiled language like C or C++. It looks very, very simple compared to C/C++ and according to them it was born from their frustrations with said languages. This has potential to become popular should they drive it sufficiently.

The syntax of Go looks like a mix of Python, C, Java and Pascal. Have a look at this:

package main

import (
    "os";
    "flag";  // command line option parser
)

var omitNewline = flag.Bool("n", false, "don't print final newline")

const (
    Space = " ";
    Newline = "\n";
)

func main() {
    flag.Parse();   // Scans the arg list and sets up flags
    var s string = "";
    for i := 0; i < flag.NArg(); i++ {
        if i > 0 {
            s += Space
        }
        s += flag.Arg(i)
    }
    if !*omitNewline {
        s += Newline
    }
    os.Stdout.WriteString(s);
}

I can say this: It looks friendly! I like the sugar.

Some of the features makes a lot of sense and I hope this will evolve successfully. Just look at the names behind this little experimental project and you’re bound to get excited! I’d love to know what C and C++ stalwarts think.

PS: Love the origin of the name:

“Ogle” would be a good name for a Go debugger.

I concur.

# python manage.py test
Creating test database...
Creating table auth_permission
Creating table auth_group
Creating table auth_user
Creating table auth_message
Creating table django_content_type
Creating table django_session
Creating table django_site
Installing index for auth.Permission model
Installing index for auth.Message model
EE..E...EEEEEEE..................
======================================================================
ERROR: test_password_change_fails_with_invalid_old_password (django.contrib.auth.tests.views.ChangePasswordTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Library/Python/2.6/site-packages/django/contrib/auth/tests/views.py", line 156, in test_password_change_fails_with_invalid_old_password
    'new_password2': 'password1',
  File "/Library/Python/2.6/site-packages/django/test/client.py", line 313, in post
    response = self.request(**r)
  File "/Library/Python/2.6/site-packages/django/core/handlers/base.py", line 92, in get_response
    response = callback(request, *callback_args, **callback_kwargs)
  File "/Library/Python/2.6/site-packages/django/contrib/auth/decorators.py", line 78, in __call__
    return self.view_func(request, *args, **kwargs)
  File "/Library/Python/2.6/site-packages/django/contrib/auth/views.py", line 160, in password_change
    }, context_instance=RequestContext(request))
  File "/Library/Python/2.6/site-packages/django/shortcuts/__init__.py", line 20, in render_to_response
    return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs)
  File "/Library/Python/2.6/site-packages/django/template/loader.py", line 103, in render_to_string
    t = get_template(template_name)
  File "/Library/Python/2.6/site-packages/django/template/loader.py", line 81, in get_template
    source, origin = find_template_source(template_name)
  File "/Library/Python/2.6/site-packages/django/template/loader.py", line 74, in find_template_source
    raise TemplateDoesNotExist, name
TemplateDoesNotExist: registration/password_change_form.html
...

In total 10 tests failed. At first I thought this was wrong. There must be something wrong with my Django installation. I consulted the Django documentation on testing Django apps and all I could pick up was that when you run python manage.py test it runs the tests of all your INSTALLED_APPS in the settings.py file.

After a bit of searching, I saw a ticket was created for this and was closed with a wontfix resolution. It made sense since it is test cases that was not implemented yet. Doh! Test Driven Development.

I do think it could be useful if they added this to the Django docs as a note for n00bs like me.

I think I can give you an executive summary of this blog post: if the documentation for an open source project sucks, nobody but the most hardcore developers will use it.

That couldn’t be more true! The documentation is just about as important as the application. The problem is that it takes time to maintain. Often we as developers are simply too lazy and “will update the documentation later”. I know I am like that, sadly… Will make it next years new years resolution to change that!

I do think that there could possibly be better ways to do documentation. Look at PHP

‘s documentation. It is fairly simple and concise, but I have often found great value in the user comments and examples which you would find underneath every page. I don’t think it is perfect, but it sure helps.

User contributions play a big role in Open Source documentation and developers with blogs often write their examples on their blogs. I end up finding them by searching Google for it, but it would sure help much more if those posts were linked to the documentation. Something to consider, I think.

“Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.”

:)

To alleviate load off the system and data transfers, you can do a HTTP conditional GET which basically check the RSS feed’s HTTP headers to see whether or not the feed was updated since the last time you checked and if it was, you’ll process the feed, else just ignore it. It does this by checking the ETag and Last-Modified-Date HTTP header attributes. It also only fetches the headers and not the entire feed, so only a fraction of the data is retrieved.

...
req = urllib2.Request(url)

req.add_header("If-None-Match", etag)
req.add_header("If-Modified-Since", lastmodified)

opener = urllib2.build_opener(NotModifiedHandler())
url_handle = opener.open(req)

if hasattr(url_handle, 'code') and url_handle.code == 304:
    return
else:
    headers = url_handle.info()
    new_etag = headers.getheader("ETag")
    new_last_modified = headers.getheader("Last-Modified")

    if new_etag != None and new_last_modified != None:
        store_new_etag(new_etag, new_last_modified, self.id)

    #get the content and write to file
    content = url_handle.read()
...

If you’re interested to know the more technical aspects of what happens, see this brilliant post. If you plan to build a feed reader at all, you need to use this function. You will not only kill your bandwidth, but everybody else’s if you don’t use it. If you built your own blogging platform, you need to make sure that you add the necessary ETag and Last-Modified-Date headers to your RSS feed. Will tell you next time how to do that. If you are on WordPress, Blogger or Movable Type it should be fine.

ImportError: Could not import settings 'mysite.settings'
(Is it on sys.path? Does it have syntax errors?):
No module named mysite.settings

My wsgi file looked like this:

import os, sys
sys.path.append('/home/djangoprojects/mysite/')
os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings'

import django.core.handlers.wsgi

_application = django.core.handlers.wsgi.WSGIHandler()

def application(environ, start_response):
    if environ['wsgi.url_scheme'] == 'https':
        environ['HTTPS'] = 'on'
    return _application(environ, start_response)

Like an idiot, I was looking everywhere for the issue, accept the glaring obvious reason. I checked permissions, created a .pth file for the project in the /site-packages/ directory in the Python library. Trust me, I did everything, but the obvious thing.

See, here is that obvious reason:

I append the directory “/home/djangoprojects/mysite” to my sys.path which is wrong. Python then looks for the module “mysite” in the directory /home/djangoprojects/mysite which in fact doesn’t exist. Obvious, no?

To fix this problem, you need to append the directory “/home/djangoprojects/” to your sys.path and it will find the module mysite.settings no problem and it will run smooth.

Long weekend, surf on the brain. That’s what is wrong!

Here is a small example of how to write a typical deploy script with Python Fabric:

First, define your various servers which you need to deploy to. Ideally, you’ll have a test, staging and live server. Thus you’ll set them up as follows.

def test():
    config.fab_user = 'test_user_name'
    config.fab_hosts = ['test.yourserver.com']

def staging():
    config.fab_user = 'staging_user_name'
    config.fab_hosts = ['staging.yourserver.com']

def live():
    config.fab_user = 'live_user_name'
    config.fab_hosts = ['www1.yourserver.com', \
'www2.yourserver.com', 'www3.yourserver.com']

This allows you to deploy your code to the various servers. Please note, you need to setup automatic login for your different servers. See here how to do automatic logins.

Next, write the steps you would take to deploy your site manually:

def deploy():
    "Deploy code to servers"
    msg = "deploying"
    require('fab_hosts', provided_by = [test,staging,live])
    local('svn ci -m "$(msg)"')
    run('svn export repos /path/to/repository/export/')
    run('cp -R /path/to/repository/export/* /path/to/your/site/')

To deploy to the staging server you can run the following command:

$ fab staging let:msg="Reason for check in" deploy

To deploy to the 3 live servers, all you do is:

$ fab live let:msg="Reason for check in" deploy

The command works as follows: fab is the command. live/stating/test are the environments you would like to load. If you said staging, it will do the commands in deploy for the staging server. The last part is the command you want to run. In this instance, deploy.

The let:msg=”Reason for check in” is the coolest bit! It basically allow you to override Fabric variables. If you look closely, in my deploy script I’ve set a variable msg to just say “deploy”. Now that is a stupid SVN message for a commit. In order to commit with meaningful messages, I override the msg variable with my own message. Simple, yet very effective!

You may want to write a number of different functions in a single fabfile. If you have 100 commands and you’re not one hundred percent sure, just do a:

$ fab list

and all the commands available to you will be printed with their description. Fabric rocks! Seriously.

I first fired up the interactive Python interpreter by simply typing the command python. Next, I imported the datetime module. Did a simple timedelta between two datetime objects and Jack’s your uncle.

$ python
Python 2.5.1 (r251:54863, Apr 15 2008, 22:57:26)
[GCC 4.0.1 (Apple Inc. build 5465)] on darwin
Type "help", "copyright", "credits" or "license"
for more information.
>>> import datetime
>>> print (datetime.date(2009, 03, 31) \
... - datetime.date(2009, 02, 06)).days
53
>>>

Python not only is an excellent programming language, it is also a brilliant general purpose toolbox! Bash/Awk/whatever experts, is there a quicker way maybe? Would love to know.