powellc

Johnny Cache & Management Commands

Discovered a pretty huge caveat to using Johnny Cache to speed up Django ORM queries.

Johnny Cache is a really great library that can speed up Django sites that are slowing down with large joins and complex data models. Django has a built in ORM caching mechanism, but Johnny Cache takes it one step further.

That said, there are some monsters in the undiscovered ocean. One of the big ones is,

powellc

Queryset Troubles in Django Class-based Views

So in a recent project I had a very strange publishing bug where two models out of more than a dozen or so, were tossing out 404s where a detail page should be. We had just instituted a lot of caching pieces to the project, which turned out to be red-herrings and probably had something to do with how long it took to track down this bug. But for the sake of the internet and anyone else who finds their model's publish datetimes strangely cached despite their best efforts to get them to show up, here's some good advice:

Don't use the "queryset" model attribute for your view class, override the "get_queryset" function.

In code:

powellc

#!/bin/bash -ex
cd $WORKSPACE
virtualenv -q --no-site-packages --distribute venv
source venv/bin/activate
pip install -r etc/requirements.txt
ln -fs `pwd`/local_settings_template.py `pwd`/local_settings.py
python manage.py syncdb --noinput
python manage.py migrate

powellc

sudo -u postgres dropdb <staging_db>
sudo -u postgres createdb -O <staging_user> -T <production_db> <staging_db>

powellc

echo "Your database name [Enter]: "
read YOUR_DB
echo "New owner name [Enter]: "
read NEW_OWNER

# First alter tables
for tbl in `psql -qAt -c "select tablename from pg_tables where schemaname = 'public';" $YOUR_DB` ; do  
  psql -c "alter table $tbl owner to $NEW_OWNER" $YOUR_DB ; 
done

powellc

#!/bin/bash
 
DB_BACKUP="/var/backups/databases/"
LATEST_DIR="/var/backups/databases/latest/"

DB_USER="root"
DB_PASSWD="secretttt"
HN=`hostname | awk -F. '{print $1}'`
 
# Remove backups older than 10 days

powellc

#!/bin/bash
# Location to place backups.
backup_dir="/var/backups/databases/"
nightly_dir="/var/backups/databases/latest/"
#String to append to the name of the backup files
backup_date=`date +%d-%m-%Y`
#Numbers of days you want to keep copie of your databases
number_of_days=15
databases=`psql -l -t | cut -d'|' -f1 | sed -e 's/ //g' -e '/^$/d'`
for i in $databases; do  if [ "$i" != "postgres" ] && [ "$i" != "template0" ] && [ "$i" != "template1" ] && [ "$i" != "template_postgis" ]; then    

powellc

#!/usr/bin/python
import sys
sys.path.append('<path_to_virtualenv>')

from gevent import monkey; monkey.patch_all()
from gevent.wsgi import WSGIServer
import os
import traceback
from django.core.handlers.wsgi import WSGIHandler
from django.core.management import call_command

powellc

diff --git a/src/adzone/managers.py b/src/adzone/managers.py
index 347e85e..271e36d 100644
--- a/src/adzone/managers.py
+++ b/src/adzone/managers.py
@@ -8,8 +8,15 @@ class AdManager(models.Manager):
         Returns a random advert that belongs to the specified category and zone
         
         """
-        try:
-            ad = self.get_query_set().filter(category__slug=ad_category, zone__slug=ad_zone).order_by('?')[0]

powellc

#!/bin/bash

###
###  This script simply parses ifconfig and loads a box's main IP into a shell variable
###

OS=`uname`
IP="" # store IP
case $OS in
   Linux) IP=`ifconfig  | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}' | grep 24 `;;