Why STOMP, and not directly AMQP, as I’m using RabbitMQ. No real reason, but the fact that there are less dependencies on a STOMP client, as it’s just a socket with text sent.

Implementations

There are several implementations of the STOMP protocol for Python. The module I chose is python-stomp (version 0.2.9), from Benjamin W. Smith. It’s simple and easy to understand.

Simple Code Examples

sto_send.py:

1
2
3
4
5
6

from stompy.simple import Client
 
stomp = Client(host='rabbitmq2')
stomp.connect(username='guest',password='noneofyourbusiness')
stomp.put('Thomas est une b*te à Tetris...', destination='/queue/jeuvideo')
stomp.disconnect()

sto_receive.py:

1
2
3
4
5
6
7
8
9
10
11
12

from stompy.simple import Client
 
stomp = Client(host='rabbitmq2')
stomp.connect(username='guest',password='noneofyourbusiness')
stomp.subscribe('/queue/jeuvideo')
message = stomp.get()
 
print message.body
 
#stomp.ack(message)
stomp.unsubscribe('/queue/video')
stomp.disconnect()

Everything is working fine, when launching sto_receive.py, I receive the message. But when I launched several receivers, I noticed, that ONLY ONE programs received the message! After some research, I found the answer: As documented in the RabbitMQ wiki, the default exchange is ‘direct’:

[...]when messages leave a queue for a consumer, they are not duplicated. One message, sitting on a queue, is delivered to only one of the available consumers. [...] If there are multiple clients, all SUBSCRIBEing to the same queue, then there will be multiple consumers all on the same queue, leading to round-robin delivery to those clients.

There is an explanation on how to change the behaviour, by changing the exchange type, and some of particular bits (like the id). I even found an example of modification for use in the equivalent STOMP Ruby module.

Here are the modifications. The good news is that there is no need to patch the stompy module, as the author provided the possibility to pass arbitrary parameters to the headers by the use of the ‘conf’ variable.

The important points are:

• You need to define an exchange of type amq.topic
• You need to set an id, which is different for each client
• As you’re using topics, you’ll have to specify a routing_key

sto_receive.py:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

from stompy.simple import Client
import uuid
 
unique_id = uuid.uuid4()
 
stomp = Client(host='rabbitmq2')
stomp.connect(username='guest',password='nonononono')
 
stomp.subscribe('',
                conf={'exchange': 'amq.topic',
                      'routing_key':'x.#',
                      'id': unique_id,
                      })
 
# Wait for a message to appear
while 1:
    message = stomp.get()
    print message.body
 
#stomp.ack(message)
stomp.unsubscribe('',conf={'id': unique_id})
stomp.disconnect()

sto_send.py:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

from stompy.simple import Client
 
 
 
stomp = Client(host='rabbitmq2')
stomp.connect(username='guest',password='nonononono')
 
 
for i in range(10000):
 stomp.put('Thomas est une b*te au Tetris...', destination='x.y',
          conf={'exchange':'amq.topic',
                #  'routing_key':'x.y'
                })
 
stomp.disconnect()

Related posts

• How to dial a number using Asterisk and Python (1)

DEPRECATION NOTICE: Files found in modules without specifying ‘modules’ in file path will be deprecated in the next major release.

If you get this warning in your puppet logs, you should take action (only if you don’t have any Puppet agent with a version <= 0.24) and modify all you references to file resources.
For example, if you have a module named 'ssh', normally, up to puppet 0.25 you would reference a file to it as:

source => ["puppet:///ssh/authorized_keys",]

But now, you need to insert a ‘module’ identifier in between like this:

source => ["puppet:///modules/ssh/authorized_keys",]

Just a small note: It seems that the templates do not need any modification.

Related posts

• Synchronization methods of a file with Puppet (0)

Related posts

• No related posts.

Related posts

• Ido’s chess Journey: How to teach chess to a 3 year old kid (1)
• Easy chess games for kids (mate in one) (5)

The problem appears when you have your Asterisk in a Xen environment. Xen does not allow the use of the RTC, so when using Dahdi/meetme, you get the following in you logs:

res_timing_dahdi.c: Asterisk has detected a problem with your DAHDI configuration and will shutdown for your protection.

So get the sources, and let’s patch it!

svn co http://svn.digium.com/svn/dahdi/linux-complete/trunk DAHDI

In dahdi_dummy.c, you’ll have to comment the two defines USE_RTC, as in a Xen, you can’t use it:

# diff -u dahdi_dummy.c.ori dahdi_dummy.c
--- dahdi_dummy.c.ori	2009-03-23 09:50:36.000000000 +0000
+++ dahdi_dummy.c	2009-03-23 08:55:38.000000000 +0000
@@ -59,11 +59,11 @@
 #if defined(CONFIG_HIGH_RES_TIMERS) && LINUX_VERSION_CODE >= VERSION_CODE(2,6,22)
 #define USE_HIGHRESTIMER
 #else
-#define USE_RTC
+//#define USE_RTC
 #endif
 #else
 #if 0
-#define USE_RTC
+//#define USE_RTC
 #endif
 #endif
 #endif

Then compile the module, as usual, with :

/etc/init.d/dahdi stop
make all
make install
make config

Verify that your module has been correctly installed:

ls -al ./2.6.24-19-xen/dahdi/dahdi_dummy.ko

Comment out all the defined modules in the /etc/dahdi/modules file.

/etc/init.d/dahdi start
# dmesg
1007539.576458] dahdi: Telephony Interface Registered on major 196
[1007539.576468] dahdi: Version: SVN-trunk-r6201M
[1007540.642839] dahdi: Registered tone zone 2 (France)

Related posts

• How to dial a number using Asterisk and Python (1)
• Asterisk cirpack problem with Free and freephonie.net (0)

Making the difference between the two urls calls at the template level is a problem because it’s managed by generic views, so the same template is used.

Anyways, there are several possibilities:

In urls.py, use the ‘template_name’ variable, where you can speficy a specific template for this url(). That is instead of using the default <model>_form.html.
What I don’t like in this situation, is that I will have two nearly similar templates, just for an added menu. Not cool. Another problem is that I use a loop to create all my urls. So if I add a special template, I’ll add it to ALL my models :-(.

Another solution, is to find a way to use a variable in the template that would be different wether the template has been loaded by update_object or create_object.

In our urlpatterns in urls.py, we can use the ‘extra_context‘ variable (takes a dictionnary as parameter). It is correctly managed, even when using generic views. So, you’ll have :

url(r'foo/ajouter/$', 'django.views.generic.create_update.create_object',  
		dict(form_class=modelForm,
                extra_context={'usage':'create'},
                name='foo_create',))
 
url(r'foo/%s/(?P<object_id>\d+)/modifier/$',
                'django.views.generic.create_update.update_object',
		dict(form_class=modelForm,
                extra_context={'usage':'modify'},
                name='foo_update'))

We can also use, in urls.py, the ‘context_processors’ variable. For more information about the context processors, have a look at this tutorial. The goal is to add ‘django.core.context_processors.request’, like this:

from django.core.context_processors import request

and in the url(), add context_processors:

url(r'foo/ajouter/$', 'django.views.generic.create_update.create_object',  
		dict(form_class=modelForm,
		context_processors=[request,]),
                name='foo_create',))

The last possiblity is a more global solution. It’s like the context_processors usage above, but added into every templates automatically.
To do this, you’ll have to edit the list of Template Processors in your settings.py file. That list is run each time a template is loaded, and allows one to add any variable to the template automatically. By default (on Django 1.0.x) this list is commented out, so it has by default the list:

("django.core.context_processors.auth",
"django.core.context_processors.debug",
"django.core.context_processors.i18n",
"django.core.context_processors.media")

You’ll have to uncomment it, and add ‘django.core.context_processors.request’. By doing this, you get the variable ‘request.path’ available in your template.

Finally, you’ll be able to test your variable with {% ifequal %} and display your conditional elements.

Related posts

• No related posts.

Related posts

• No related posts.

This is not really a problem, but an annoyance, as it fills up your logs. This is a known problem for more than years, but has never been corrected (neither by Asterisk nor by Cirpack devs). The usual correction was to add the following line to your startup scripts (/etc/rc.local on Debian for example):
iptables -A INPUT -p udp -m udp --dport 5060 -m string --string "Cirpack KeepAlive Packet" -j DROP

But the syntax has changed in iptables, and you’ll get the error:
iptables v1.3.6: STRING match: You must specify `--algo'

so, just add one of the 2 available algorithms (bm and kmp):
iptables -A INPUT -p udp -m udp --dport 5060 -m string --string "Cirpack KeepAlive Packet" --algo bm -j DROP


Related posts

• How to dial a number using Asterisk and Python (1)
• Asterisk: DADHI module not working when using Xen (5)

At first I thought I’d create the endings myself, for example, using online diagrams generators or using Wikipedia/MediaWiki’s templates, but it was not so easy, so I thought about making a program to generate them.
Generating one from scratch would take me time I really don’t have, and there are just two python modules that give high-level functions to chess.
So I started looking for projects similar to mine, that include games with mate in one. I found a small database of mate in one on my favorite chess website, in the download section: a Chessbase datafile with 1171 mate in one studies! So cool.

Well, It was really a pain to convert that Chessbase (.cbv) file, as the only program able to convert to PGN is running on Windows　(at least it’s free). You just have to follow the instructions from this thread.
After getting a nice PGN file, just open it with scid, go to “Tools”, then select “Write the filter”, and choose LaTeX. You’ll get a TeX file. Use you favorite TeX generator (Live TeX seems to be the one today), like this for example, to generate directly a PDF file:

cat mat_temp.tex |grep -v "\\\\$" > mate_in_one.tex
latex --output-format=pdf mate_in_one.tex

(Yes I had to cleanup a bit the file before generating the .pdf)

The result is here, 196 pages of tests (6 one each page) if you don’t want to fight with the missing TeX modules (you’ll need chess12.sty) and get a nice result.

I’m sure many people search for this kind of file, so I’m pretty happy to help other parents/coaches.

White mate in one

Edit: I added a PDF version without the solution included.

Related posts

• Ido’s chess Journey: How to teach chess to a 3 year old kid (1)
• New chess website for Chess education/promotion (0)

Here are some ideas (some not yet implemented):

• Using a DIY plastified chess board, allows me to show/play different positions really fast, anywhere.
• Colorize squares where a piece is allowed to go :
  

  

• Pawn race games (no en-passant rule yet).
• Really small games (must not go over 5 minutes) with reduced chess set (for example Queen and 3 pawns vs Knight, bishop and 3 pawns).
• Checkmate in one, using DiagTransfer program to draw series of chess diagrams. This program works only on Windows, but it works fine with Wine.
  

  

  For quick single diagrams, I found wbeditor, an online javascript diagram generator.

There’s a thread (french) about experience from different teachers, giving really good advices.
Most notably, Véronique Houck who has 15 years of experience of teaching chess to kindergarten/maternelle children. She wrote two books (in french). One is named Bibou & le monde des échecs, and the other one Le jeu d’échecs au cycle2. It’s not so easy to find, but using Google, you can find shows many links.

I’ve not yet read them. I’ll make a review when I get them.

Related posts

• Easy chess games for kids (mate in one) (5)
• New chess website for Chess education/promotion (0)