Install RabbitMQ

install server itself (using port)

MacOs X:

sudo port install rabbitmq-server

Ubuntu:

sudo apt-get install rabbitmq-server

create user, vhost and set some permissions:

rabbitmqctl add_user username password
rabbitmqctl add_vhost /vhost
rabbitmqctl set_permissions -p /vhost username ".*" ".*" ".*"

done.

OSError: [Errno 38] Function not implemented

Server: Ubuntu 11.04

Run celeryd with info log level

$ ./manage.py celeryd -l info
[2012-02-01 01:16:45,779: ERROR/MainProcess] Unrecoverable error: OSError(38, 'Function not implemented')
Traceback (most recent call last):
  File "/var/www/th4x/.env/lib/python2.7/site-packages/celery/worker/__init__.py", line 268, in start
    component.start()
  File "/var/www/th4x/.env/lib/python2.7/site-packages/celery/concurrency/base.py", line 72, in start
    self.on_start()
  File "/var/www/th4x/.env/lib/python2.7/site-packages/celery/concurrency/processes/__init__.py", line 43, in on_start
    self._pool = self.Pool(processes=self.limit, **self.options)
  File "/var/www/th4x/.env/lib/python2.7/site-packages/celery/concurrency/processes/pool.py", line 520, in __init__
    self._setup_queues()
  File "/var/www/th4x/.env/lib/python2.7/site-packages/celery/concurrency/processes/pool.py", line 695, in _setup_queues
    self._inqueue = SimpleQueue()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 354, in __init__
    self._rlock = Lock()
  File "/usr/lib/python2.7/multiprocessing/synchronize.py", line 147, in __init__
    SemLock.__init__(self, SEMAPHORE, 1, 1)
  File "/usr/lib/python2.7/multiprocessing/synchronize.py", line 75, in __init__
    sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue)
OSError: [Errno 38] Function not implemented
[2012-02-01 01:16:45,780: INFO/MainProcess] process shutting down

Python's _multithreading requires /dev/shm to work. In Ubuntu /dev/shm points to /run/shm by default. Rename (or delete, I doubt it is necessary anymore) existing /dev/shm.

Create /dev/shm directory

$ sudo -i  # get root
$ mkdir /dev/shm

Add to /etc/fstab mounting of /dev/shm command

tmpfs /dev/shm    tmpfs   defaults,noexec,nosuid     0     0

Mount all unmounted filesystems from /etc/fstab.

$ mount -a

There should be no errors.

Run again

$ ./manage.py celeryd -l info

It starts normally.

PostgreSQL autostart on Mac OS X

I installed PostgreSQL 9.0 from „One Click Installer” and didn't want it to launch as system starts.

As PostgreSQL has been installed launchctl takes responsibility to take care of always running PostgreSQL daemon. /Library/LaunchDaemons/com.edb.launchd.postgresql-9.0.plist file sets up the daemon's behavior.

There are two options that can prevent the daemon after start up.

<key>Disabled</key>
<false/>

<key>RunAtLoad</key>
<true/>

„Disabled”=True prevents the job from loading at all and there will be not possible start the job even manually.
„RunAtLoad”=Fasle tells the launchctl not to run the job after loading.

Here we are, set „RunAtLoad” to False and the daemon won't be run automatically.

By the way, there are useful commands below to run and stop the daemon though:

sudo launchctl list | grep postgresql

display current daemon's pid or exit code.

sudo launchctl start com.edb.launchd.postgresql-9.0

start the daemon

sudo launchctl stop com.edb.launchd.postgresql-9.0

and stop it

Tab-completion for django-admin.py and manage.py

Download django_bash_completion file and save in some convenient place in your system. In .bash_profile (or .bashrc if it doesn't envoke .bash_profile) add

. ~/path/to/django_bash_completion

Settings will take effect the next time you log in.

Autoselection of checkboxes in a table

The code doing selection

$(function () {
    "use strict";
    var toggleSelect = $("#all"),
        checkboxes = $("#table").find("tbody input[type=checkbox]");
    toggleSelect.click(function () {
        checkboxes.attr('checked', $(this).is(":checked"));
    });
    checkboxes.click(function () {
        toggleSelect.attr('checked', checkboxes.length === checkboxes.filter(':checked').length);
    });
});

A sample table

         
         
Username
         
Phone Number
     
     

         
         
User 1
         
0123456789
     
         
         
User 2
         
0133456789
     
 

Activate VE from Django's manage.py

To transparently activate virtual environment from project's manage.py insert the code below right after #!/usr/bin/env python

activate_this = '/ABSOLUTE/PATH/TO/ENVIRONMENT/FILES/bin/activate_this.py'
execfile(activate_this, dict(__file__=activate_this))

Madly follow PEP8 with git help

If you intended or are obliged to strictly comply to PEP8 it may be useful to have a git hook that takes care of checking your code before you have committed and prevents you from amending previous commit again and again.

So, in .git/hooks/ directory of your repository create a file with name pre-commit and put

#!/bin/sh

# comma-separated list of files and directories which are not for checking
SKIP=migrations,bootstrap.py,dodo.py,manage.py

pep8 -r --exclude=$SKIP .

UPDATE: The code above checks all the project Python files. To limit checking only for files going to be committed

#!/bin/sh

FILES=$(git diff --cached --name-status | awk '$1 $2 { print $2}' | grep -e \.py$)
if [ -n "$FILES" ]; then
    pep8 -r $FILES
fi

The command shows all staged files, next only the filenames are left and filters Python files. If any they are to be checked with PEP8 utility.

Word and text translation bookmarklet

Sometimes (I hope rarer and rarer :)) I need to translate an unknown foreign word on the page. I used to select it, open Google Dictionary Translate, paste it, set source and destination languages if needs and only then press the button to translate it.

Some time later I discovered bookmarklets. I liked the approach and made one for myself.

Drag this link En<>Ru the bookmark panel to be able translate words or text.

To change default source and destination languages put their codes in place of en and ru.

Source code.

(function() {
    var t;
    try {
        t= ((window.getSelection && window.getSelection()) ||
            (document.getSelection && document.getSelection()) ||
            (document.selection &&
            document.selection.createRange &&
            document.selection.createRange().text));
    }
    catch(e){
        t = "";
    }

    if(t && (t=t.toString()) && t.length){
window.open("http://translate.google.com/?sl=en&tl=ru&hl=en&text="+t+"#en|ru|"+t);
    }
})()

I used Javascript Compressor to get compressed version to use it in the bookmarklet.

Uninstall XCode

To uninstall XCode from Mac OS X run in terminal:

sudo /Developer/Library/uninstall-devtools –mode=all

Upgrading Mac OS X to Lion and dealing with virtualenv

I happened to have successfully upgraded my Snow Leopard to Lion. It looks nicer, softer and so forth. But I depend on my MacBook Pro in my work and have to have everything working.

Actually after upgrade everything were broken: python did not work properly, system paths were set in their defaults. So it was absolute mess.

First, as I learned it from Snow Leopard, I have downloaded new XCode from Mac App Store. It quote big and it took all night (while I was sleeping) for downloading. In the morning I installed and all became better but one. Virtual environments were still spoiled and did not work.

After a few tries and researches I came up with the following:

sudo easy_install pip # it installs new (or even) pip version
sudo pip install virtualenvwrapper

After those commands all get working.

CKEditor autosave plugin

If you need autosave function for the CKEditor I made a plugin. It allows to save automatically the work as you've stopped typing.

UPD  Oct 6, 2011: Plugin has moved to GitHub.

Avoid command repeating in Bash

If you are already done with mess of the same commands in bash history, just put that in your ~/.bashrc

export HISTCONTROL=ignoredups:erasedups

ignoredups prevents the history from duplicates
erasedups if a command is already in the list it will be removed at the old position and put in the beginning of the history list

Clients of the webservice

Some time ago my iPhone happened to get lost. There were many clients of well known services installed and all of them had been logged in and most part of them had their passwords saved. To prevent access from my lost phone I had to change password for almost all services I used.

Clients should avoid using re-authentication with login and password. It implies saving them on the client side. Conversely, the application should either ask for OAuth authentication or for login and password only once. Latter requires the server to provide the key to login next time with.

Those techniques allow the web server to control all the clients without changing the password if something has happened to one of the clients.