Allow remote connections to MySQL server

To enable remote access for MySQL server:

$ sudo vim /etc/mysql/my.cnf
### edit my.cnf
### set bind address and comment out or remove skip-networking (if exists)

[mysqld]
...
bind-address=SERVER-EXTERNAL-IP
# skip-networking

$ /etc/init.d/mysql restart

Now it works.

{less} mix function error

Documentation tells mix function takes only two parameters, @color1 and @color2. Actually there is a mistake. The correct function definition is

mix(@color1, @color2, value)

, where value denotes how much of @color1 should appear in the result color.

Trap Ctrl C in Bash

#!/bin/bash

# call trapped in case Ctrl+C pressed
trap trapped INT

function trapped() {
    echo "CTRL-C pressed"
}

while true; do
    sleep 1
    echo -n "."
done

Setup Apache2's mod_wsgi on Ubuntu

If you get this when restarting Apache2 on Ubuntu

Invalid command 'WSGIDaemonProcess', perhaps misspelled or defined by a module not included in the server configuration
Action 'configtest' failed.

it means you don't have mod_wsgi module installed.

These commands install and enable it.

sudo apt-get install libapache2-mod-wsgi
sudo a2enmod mod-wsgi
sudo /etc/init.d/apache2 restart

Perl warning about locale in Ubuntu

If you get this warning

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
 LANGUAGE = (unset),
 LC_ALL = (unset),
 LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

it can be fixed with

locale-gen en_US.UTF-8
dpkg-reconfigure locales

Get Graphite run for a Django project

This post is intended first of all to memorize my experience of getting the Graphite system work.

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.