I am new to web development, and I am working on a basic image gallery app (learning exercise) using Django. I have it set up so I can upload a zip full of images all at once to create a new album. This all seems to work OK, but I am getting an HTTP 504 error when the uploaded file is especially large.
I gather (please correct me if I am wrong) this error means my app is too slow to return an HTTP response. I am guessing this is because it takes a long time to unzip and process (create a Pic object in the DB and create thumbnails) all the images.
Is there a way to return a response (say to some intermediate page) while still performing the processing in the background - maybe using threads? What is the proper way to handle this? Is it time for me to start learning Javascript/AJAX?
Thank you!
Models:
from django.db import models
from blog.models import Post
class Album(models.Model):
title = models.CharField(max_length=128)
slug = models.SlugField()
description = models.TextField()
parent = models.ForeignKey('self', null=True, blank=True)
pub = models.BooleanField()
date_created = models.DateTimeField(auto_now_add=True)
date_published = models.DateTimeField(null=True, blank=True)
date_modified = models.DateTimeField(auto_now=True)
def __unicode__(self):
return self.title
class Pic(models.Model):
image = models.ImageField(upload_to='pics/%Y/%m')
title = models.CharField(max_length=128)
caption = models.TextField(blank=True, null=True)
albums = models.ManyToManyField('Album', null=True, blank=True)
posts = models.ManyToManyField(Post, blank=True, null=True)
date_taken = models.DateTimeField(null=True, blank=True)
date_uploaded = models.DateTimeField(auto_now_add=True)
date_modified = models.DateTimeField(auto_now=True)
def __unicode__(self):
return self.title
View:
I'm doing this manually because I didn't grok the Django admin when I started. I think it might be better to use admin customization here.
def new_album(request):
if request.method == "POST":
form = AlbumForm(request.POST, request.FILES)
if form.is_valid():
from gallery.pic_handlers import handle_uploaded_album
pics = handle_uploaded_album(request.FILES['pic_archive'])
a = form.save()
a.slug = slugify(a.title)
a.save()
for pic in pics:
pic.albums.add(a)
return HttpResponseRedirect('/gallery/album/%s/' % a.slug)
else:
form = AlbumForm()
return render_to_response('new_album.html', {
'form' : form,
}, context_instance = RequestContext(request))
Additional processing:
def handle_uploaded_album(pic_archive):
destination = open(join(settings.MEDIA_ROOT,pic_archive.name), 'wb+')
for chunk in pic_archive.chunks():
destination.write(chunk)
destination.close()
today = datetime.date.today()
save_path = 'pics/{0}/{1:02}/'.format(today.year, today.month)
tmp_path = 'tmp/'
z = zipfile.ZipFile(join(settings.MEDIA_ROOT,pic_archive.name), 'r')
pics = []
for member in z.namelist():
if '/' in member or '\\' in member:
# don't deal with any directories inside the zip
# this also solves the '__MACOSX' issue
continue
if splitext(member)[1] in IMG_EXT:
z.extract(member,join(settings.MEDIA_ROOT,tmp_path))
im = File(open(join(settings.MEDIA_ROOT,tmp_path,member), 'rb'))
# create a Pic from this file
pic = Pic()
pic.title = member
pic.image.save(
join(save_path, member),
im,
True)
create_thumbnails(pic)
im.close()
# remove extracted images
remove(join(settings.MEDIA_ROOT,tmp_path,member))
# TODO: save date taken if available
pics.append(pic)
z.close()
remove(join(settings.MEDIA_ROOT,pic_archive.name))
return pics
def create_thumbnails(pic):
fname, ext = splitext(pic.image.path)
img = Image.open(pic.image.path)
img.thumbnail((512,512), Image.ANTIALIAS)
img.save(fname + '_m' + ext)
img.thumbnail((128,128), Image.ANTIALIAS)
img.save(fname + '_s' + ext)
