Cowboy development with Django

Cowboy development with Django Simon Willison DjangoCon 2009

http://www.youtube.com/watch?v=nZx9sNXv9h0

Just one problem... we didn’t have cowboys in England

The Napoleonic Wars

A Napoleonic Sea Fort http://en.wikipedia.org/wiki/File:Alderney_-_Fort_Clonque_02.jpg

Super Evil Dev Fort

http://www.anotherurl.com/travel/fort_clonque/handbook.htm

Photos by Cindy Li http://www.ﬂickr.com/photos/cindyli/sets/72157610369683426/

WildLifeNearYou.com (Built in 1 week and 10 months)

Search uses the geospatial branch of Xapian Species database comes from Freebase Photos can be imported from Flickr “Suggest changes” to our Zoo information uses model objects representing proposed changes to other model objects

/dev/fort Cohort 3: Winter 2009 What is /dev/fort? The trip Imagine a place of no distractions, no The third /dev/fort will run from 9th to 16th November on the Kintyre IM, no Twitter — in fact, no Peninsula in Scotland. internet. Within, a group of a dozen or more developers, designers, thinkers and doers. And a lot of a food. Cohort 2: Summer 2009 Now imagine that place is a fort. The trip The second /dev/fort ran from 30th May to 6th June 2009 at Knockbrex Castle in Scotland. As with the first cohort, we have a few remaining problems still to iron out (thorny issues inside Django we were hoping to avoid, that sort of thing). We hope to have the site in alpha by the end of the summer. Cohort members Ryan Alexander, Steven Anderson, James Aylett, Hannah Donovan, Natalie Downe, Mark Norman Francis, Matthew Hasler, Steve Marshall, Richard Pope, Gareth Rushgrove, Simon Willison. The idea behind /dev/fort is to throw Cohort 1: Winter 2008 a group of people together, cut them off from the rest of the world, and http://devfort.com/

Cowboy development at work

MP expenses

Heather Brooke

January 2005 The FOI request

February 2008 The Information Tribunal

“Transparency will damage democracy”

January 2009 The exemption law

March 2009 The mole

“All of the receipts of 650-odd MPs, redacted and unredacted, are for sale at a price of £300,000, so I am told. The price is going up because of the interest in the subject.” Sir Stuart Bell, MP Newsnight, 30th March

8th May, 2009 The Daily Telegraph

At the Guardian...

April: “Expenses are due out in a couple of months, is there anything we can do?”

June: “Expenses have been bumped forward, they’re out next week!”

Thursday 11th June The proof-of-concept

Monday 15th June The tentative go-ahead

Tuesday 16th June Designer + client-side engineer

Wednesday 17th June Operations engineer

Thursday 18th June Launch day!

How we built it

$ convert Frank_Comm.pdf pages.png

Frictionless registration

Page ﬁlters

page_filters = ( # Maps name of filter to dictionary of kwargs to doc.pages.filter() ('reviewed', { 'votes__isnull': False }), ('unreviewed', { 'votes__isnull': True }), ('with line items', { 'line_items__isnull': False }), ('interesting', { 'votes__interestingvote__status': 'yes' }), ('interesting but known', { 'votes__interestingvote__status': 'known' ... ) page_filters_lookup = dict(page_filters)

pages = doc.pages.all() if page_filter: kwargs = page_filters_lookup.get(page_filter) if kwargs is None: raise Http404, 'Invalid page filter: %s' % page_filter pages = pages.filter(**kwargs).distinct() # Build the filters filters = [] for name, kwargs in page_filters: filters.append({ 'name': name, 'count': doc.pages.filter(**kwargs).distinct().count(), })

Matching names

http://github.com/simonw/datamatcher

On the day

def get_mp_pages(): "Returns list of (mp-name, mp-page-url) tuples" soup = Soup(urllib.urlopen(INDEX_URL)) mp_links = [] for link in soup.ﬁndAll('a'): if link.get('title', '').endswith("'s allowances"): mp_links.append( (link['title'].replace("'s allowances", ''), link['href']) ) return mp_links

def get_pdfs(mp_url): "Returns list of (description, years, pdf-url, size) tuples" soup = Soup(urllib.urlopen(mp_url)) pdfs = [] trs = soup.findAll('tr')[1:] # Skip the first, it's the table header for tr in trs: name_td, year_td, pdf_td = tr.findAll('td') name = name_td.string year = year_td.string pdf_url = pdf_td.find('a')['href'] size = pdf_td.find('a').contents[-1].replace('(', '').replace(')', '') pdfs.append( (name, year, pdf_url, size) ) return pdfs

“Drop Everything”

Photoshop + AppleScript v.s. Java + IntelliJ

Images on our docroot (S3 upload was taking too long)

Blitz QA

Launch! (on EC2)

Crash #1: more Apache children than MySQL connections

unreviewed_count = Page.objects.ﬁlter( votes__isnull = True ).distinct().count()

SELECT COUNT(DISTINCT èxpenses_page`.ìd`) FROM èxpenses_page` LEFT OUTER JOIN èxpenses_vote` ON ( èxpenses_page`.ìd` = èxpenses_vote`.`page_id` ) WHERE èxpenses_vote`.ìd` IS NULL

unreviewed_count = cache.get('homepage:unreviewed_count') if unreviewed_count is None: unreviewed_count = Page.objects.ﬁlter( votes__isnull = True ).distinct().count() cache.set('homepage: unreviewed_count', unreviewed_count, 60)

With 70,000 pages and a LOT of votes... DB takes up 135% of CPU Cache the count in memcached... DB drops to %35 of CPU

unreviewed_count = Page.objects.ﬁlter( votes__isnull = True ).distinct().count() reviewed_count = Page.objects.ﬁlter( votes__isnull = False ).distinct().count()

unreviewed_count = Page.objects.ﬁlter( is_reviewed = False ).count()

Migrating to InnoDB on a separate server

ssh mps-live "mysqldump mp_expenses" | sed 's/ENGINE=MyISAM/ENGINE=InnoDB/g' | sed 's/CHARSET=latin1/CHARSET=utf8/g' | ssh mysql-big "mysql -u root mp_expenses"

Reigning in the cowboy

Reigning in the cowboy An RSS to JSON proxy service Pair programming Comprehensive unit tests, with mocks Continuous integration (Team City) Deployment scripts against CI build numbers

Points of embarrassment Database required to run the test suite Logging? What logging? Tests get deployed alongside the code (!) ... but generally pretty smooth sailing

A ﬁnal thought

Web development in 2005 Relational Cache Database Application Admin tools Templates XML feeds

Web development in 2009 Relational Search Datastructure External web Non-relational Cache Database index servers services database Admin tools Application Message queue Ofﬂine workers Monitoring and reporting Templates XML feeds API Webhooks

Thank you

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Cowboy development with Django

by Simon Willison

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