Everything installed just splendidly using brew install mysql, but I have a particularly heavy query on a dev site and the server was responding with “MySQL server has gone away.” No errors were showing up in the .err file (/usr/local/var/mysql) until I used mysql.server start --log-warnings=2. It turned out this was because the max_allowed_packet was too small, so I started the server with mysql.server start --max-allowed-packet=16M and I was golden.

So, I went to put this in my my.cnf file… but there wasn’t one!! I couldn’t find any configurations anywhere! Seemed really weird until I realized that mysql.server was actually running msqld with all the options passed in. So, I tried creating an /etc/my.cnf file and then ~/.my.cnf, but they didn’t work. I kept getting errors like:

ERROR! MySQL server PID file could not be found!
or
ERROR! The server quit without updating PID file
or
ERROR! The server quit without updating PID file (/usr/local/var/mysql/cambiodos.local.pid)

I think this may have had something to do with my setting the mysql user to myself. Shit, it seemed to make sense at the time. So, with “ERROR” ringing in my head and my blood pressure rising, I read on the MySQL site somewhere that ~/.my.ini was an alternative to ~/.my.cnf. For some reason it made sense to me to try it and it worked.

I’m guessing this has something to do with the fact that my.cnf is a configuration file and my.ini is just settings? So by using the .ini file I was able to simply override settings, not the absolute configuration, but that’s just a guess. Anyway, I’m happily running mysql with the following ~/.my.ini file:

[mysqld]
max_allowed_packet = 16M
log_warnings = 2
default-character-set = utf8

from django.newforms.fields import MultipleChoiceField
from appengine_django.models import BaseModel

class ListPropertyChoice(MultipleChoiceField):

    def clean(self, value):
        """ extending the clean method to work with GAE keys """
        new_value = super(ListPropertyChoice, self).clean(value)
        key_list = []
        for k in new_value:
            key_list.append(BaseModel.get(k).key())
        return key_list

You can then use this in your forms:

...
from fields import ListPropertyChoice

class Form(djangoforms.ModelForm):
    my_model = ListPropertyChoice(
                        widget=forms.CheckboxSelectMultiple(),
                        choices=[(m.key(), m.name) for m in db.Query(MyModel)]
                    )
    class Meta:
        model = ParentModel

Obviously you can use both the SelectMultiple widget and the CheckboxSelectMultiple widget and this same process could be easily duplicated for ChoiceField:

class GAEChoiceField(ChoiceField):
    def clean(self, value):
        """ extending the clean method to work with GAE keys """
        value = super(GAEChoiceField, self).clean(value)
        return BaseModel.get(value).key()

Scott’s Field used the post_init and pre_save signals, which is probably the right way… Since this wasn’t working anymore, I decided to use the post_save signal. This way the image or file would be saved to a temporary directory initially and then moved to the appropriate directory afterwards.

Here is how the field would be defined in the model:

    class Image(models.Model):
	file = CustomImageField(use_key=True, upload_to='tmp')

use_key and upload_to are optional. use_key defaults to False. If it is True then the id of the instance will be used as a prefix for the new file as there is the potential for overwriting now that we are moving the file. upload_to will simply define the temporary directory to upload the files to initially.

Below is the code that defines the CustomImageField. I have this in a file called “custom_fields.py.”

from django.db.models import ImageField, FileField, signals
from django.dispatch import dispatcher
from django.conf import settings
import shutil, os, glob, re
from distutils.dir_util import mkpath

class CustomImageField(ImageField):
    """Allows model instance to specify upload_to dynamically.

    Model class should have a method like:

        def get_upload_to(self, attname):
            return 'path/to/%d' % self.id

    Based closely on: http://scottbarnham.com/blog/2007/07/31/uploading-images-to-a-dynamic-path-with-django/
    """
    def __init__(self, *args, **kwargs):
        if not 'upload_to' in kwargs:
            kwargs['upload_to'] = 'tmp'
        self.use_key = kwargs.get('use_key', False)
        if 'use_key' in kwargs:
            del(kwargs['use_key'])
        super(CustomImageField, self).__init__(*args, **kwargs)

    def contribute_to_class(self, cls, name):
        """Hook up events so we can access the instance."""
        super(CustomImageField, self).contribute_to_class(cls, name)
        dispatcher.connect(self._move_image, signal=signals.post_save, sender=cls)

    def _move_image(self, instance=None):
        """
            Function to move the temporarily uploaded image to a more suitable directory
            using the model's get_upload_to() method.
        """
        if hasattr(instance, 'get_upload_to'):
            src = getattr(instance, self.attname)
            if src:
                m = re.match(r"%s/(.*)" % self.upload_to, src)
                if m:
                    if self.use_key:
                        dst = "%s/%d_%s" % (instance.get_upload_to(self.attname), instance.id, m.groups()[0])
                    else:
                        dst = "%s/%s" % (instance.get_upload_to(self.attname), m.groups()[0])
                    basedir = "%s%s/" % (settings.MEDIA_ROOT, os.path.dirname(dst))
                    mkpath(basedir)
                    shutil.move("%s%s" % (settings.MEDIA_ROOT, src),"%s%s" % (settings.MEDIA_ROOT, dst))
                    setattr(instance, self.attname, dst)
                    instance.save()

    def db_type(self):
        """Required by Django for ORM."""
        return 'varchar(100)'

I just started with Google App Engine the other day. Man, who could resist a free server environment?

Being a long time Django developer (one year), I was really excited about it because it “runs django”. Now this isn’t really the case because of BigTable, which isn’t a real relational database. However, if you forgo the Django ORM and use GAE models, you can still work with the other things that make Django so awesome: templates and forms. AND, the google models are so similar to Django that you’ll barely even notice the difference.

Ok, this isn’t a full on review GAE with Django, so I’ll cut right to the chase. I’m sure you found this page when you were trying to use django forms to handle the ListProperty model field in your HTML forms. The problem is that things like ModelChoiceField and ModelMultipleChoiceField won’t work because they rely on the Django ORM. For that matter, ChoiceField and MultipleChoiceField won’t work because they return a list of strings, that although they can be the string for a db.key(), they won’t be the Key objects that your new models expect for ListProperty.

So, to get around this I just adjusted the MultipleChoiceField a bit so that it returns the list chosen fields as Key objects:

#MODELS
class Toping(BaseModel):
    name = db.StringProperty(required=True)

class Pizza(BaseModel):
    name = db.StringProperty(required=True)
    toppings = db.ListProperty(db.Key)

    def get_topings(self):
        # This returns the models themselves, not just the keys that are stored in toppings
        return Topping.get(self.toppings)

#FORMS
class PizzaForm(djangoforms.ModelForm):
    toppings = ListPropertyChoice(
                        widget=forms.CheckboxSelectMultiple(),
                        choices=[(rt.key(), rt.name) for rt in db.Query(Topping)]
                    )
    class Meta:
        model = Pizza

#CUSTOM FIELD
from django.newforms.util import ErrorList, ValidationError
from django.newforms.fields import ChoiceField
from django.newforms.widgets import MultipleHiddenInput, SelectMultiple
from appengine_django.models import BaseModel

from appengine_django.serializer.python import smart_unicode
from django.utils.translation import gettext

class ListPropertyChoice(ChoiceField):
    hidden_widget = MultipleHiddenInput

    def __init__(self, choices=(), required=True, widget=SelectMultiple, label=None, initial=None, help_text=None):
        super(ListPropertyChoice, self).__init__(choices, required, widget, label, initial, help_text)

    def clean(self, value):
        """
        Validates that the input is a list or tuple.
        """
        if self.required and not value:
            raise ValidationError(gettext(u'This field is required.'))
        elif not self.required and not value:
            return []
        if not isinstance(value, (list, tuple)):
            raise ValidationError(gettext(u'Enter a list of values.'))
        new_value = []
        for val in value:
            val = smart_unicode(val)
            new_value.append(val)
        # Validate that each value in the value list is in self.choices.
        valid_values = set([smart_unicode(k) for k, v in self.choices])
        for val in new_value:
            if val not in valid_values:
                raise ValidationError(gettext(u'Select a valid choice. %s is not one of the available choices.') % val)
        # These are the only changes to the django MultipleChoice Field
        # we just convert the list of strings to a list of keys
        key_list = []
        for k in new_value:
            key_list.append(BaseModel.get(k).key())
        return key_list

Now for a quick expaination… The ListPropertyChoice class itself is really just the MultipleChoiceField from Django V0.96. I had to use this because I couldn’t get the latest svn version to work w/ App Engine due to some SafeUnicode issues I haven’t looked into yet. The only real changes to that class are the last four lines which return the list of keys instead of key-strings from the form.

The only other thing that might need explanation is the get_toppings() method that I added to the Pizza model. This is just a shortcut to access the models instead of the keys, as they’re stored in the ListProperty.

Note: you might want to backup your stuff, just in case you screw up your regular expression.

Basically, I have a bunch of files that need to have changes, such as email address, or include paths.

So, for example, in one I had to change a bunch of email addresses so I used `sed`. To do this on one file you would simply run the sed command directly:
sed -e s/info@olddomain.com/info@newdomain.com/g -i file.html
-e tags the regular expression you’re using
-i means we’re editing the files inline (not outputting the results to standard out)
Don’t forget g, because this will ensure that the expression is greedy and will find all the instances of this expression.

Of course, you probably want to run this on a bunch of files, so you would use `find`, because it’s awesome:
find -name "*.html" -exec sed -e s/info@olddomain.com/info@newdomain.com/g -i {} \;

EDIT: I have found that Macs have an issue with the inline command (-i). You need to use `-i ”` to give the inline an empty extension. So, the command above would be:

find -name “*.html” -exec sed -e s/info@olddomain.com/info@newdomain.com/g -i ” {} \;

Create your django project anywhere

~/django/projects$ ../src/trunk/django/bin/django-admin.py startproject myProject


Set up your SVN
This can be done either on your local machine or on another server. I like /var/svn/repos/myProject/.

$ svnadmin create /var/svn/repos/myProject

I use svnserve to serve my svn so I update the permissions in /var/svn/repos/myProject/conf/svnserve.conf:

[general]
anon-access = none
auth-access = write
password-db = passwd

/var/svn/repos/myProject/conf/passwd

[users]
user = passwd

(re)Start the svnserve daemon

svnserve -d -r /var/svn/repos

Finally, we’re ready to check in the project tree

$ svn import myProject file:///var/svn/repos/myProject/trunk/myProject -m "Initial import"

Now just import it into Eclipse and your good to go!

Oh, and you might want to read about excluding .pyc files in svn.

Ok, so I don’t know why this works, but it does and I haven’t seen any decrease in quality. I suspect converting from PDF to PS and back just optimizes the PDF.
Requirements

• pdftk for linux

The Process

1. Convert your PDF to PS (this creates a large file
2. Convert the new PS back to a PDF


pdf2ps large.pdf very_large.ps
ps2pdf very_large.ps small.pdf


Results
large.pdf : 6.3MB
very_large.ps : 53.4MB
small.pdf : 2.4MB
Looks like pretty good compression to me.

If anyone knows why this works so well, please let me know.

Create a file (.svnignore) with the regular expressions

*.pyc
*~


Run svn propset on the project

svn -R propset svn:ignore -F .svnignore .

-R indicates that you are doing this recursively so all the directories ignore these.
-F indicates the file we just created with the regular expressions.

EDIT 5/27/08:
If you’ve already got yourself into the mess of versioning your compiled files, then you might want to do a few things.
1) Revert all the .pyc files (you can always recompile them). You don’t want there to be any local changes when you try to delete them:
find -name "*.pyc" -exec svn revert {} \;
2) Delete all the .pyc files using `svn delete`:
find -name "*.pyc" -exec svn delete {} \;
3) Finally recompile and re-run the svn ignore code above

The design is ingenious because it can back up a variety of machines with unique settings. For windows machines I use a protected share that can only be accessed by a user called ‘backup’. The backup application then connects periodically to the share and runs incremental backups. For the linux machines I run an rsync demon on the pc. This is one of the few cases where it’s as easy on windows as linux. (In case there’s any doubt… everything is easier on linux 99% of the time.)

Given that I use linux exclusively, here’s the documentation on setting up an rsyncd connection with Backuppc.

1) Install rsyncd: $ sudo apt-get install rsync (ubuntu)
2) Configure rsyncd with a backup option (/etc/rsyncd.conf)

[backup]
path = /home/jamstooks
exclude = "/home/jamstooks/.mozilla/firefox/***"
comment = Backup
uid = jamstooks
gid = jamstooks
read only = true
auth users = backup
secrets file = /etc/rsyncd.secrets

I excluded the firefox directory, because I was getting issues with the cache being accessed during backup. It would probably be best to include the bookmarks though.
/etc/rsyncd.secrets stores the passwords in plain-text, so make sure you adjust your permissions appropriately:

backup:passwd

3) Ubuntu sets up an init.d setup file, but you want to make sure the daemon is running…
4) Finally, you are ready to set up BackupPC. In the BackupPC admin, simply select rsync for this machine and fill in the password you selected.

More details can be found in the official BackupPC documentation.

# make thumbnail filename
th_name = base + "_tn"
th_name += ext
return urlparse.urljoin(basedir, th_name)


This ensures that all my images conform to the sizes I need. However, even if the server is automatically resizing the images for me, I don’t want to spend hours uploading huge images only to have them resized. It’s just a waste of bandwidth and time. So, I’ve written a quick python script that resizes all the images in a given directory and places the copies in a new directory called resized:


#! /usr/bin/env python

files = os.listdir(image_dir)
for file in files:
if JPG.match(file):
f = image_dir.rstrip("/") + "/" + file
print f
img = PIL.open(f)
img.thumbnail(SIZE, PIL.ANTIALIAS)
img.save(get_new_path(f))