How we built and scaled Lanyrd, using Python, Django, Solr, r

1. Lanyrd.com
Building Lanyrd
Simon Willison
BrightonPy, 9th August 2011
http://lanyrd.com/sgptt

2. Lanyrd.com
Definitive database
of professional events
and speakers

3. Lanyrd.com
Definitive database Social event recommendation
of professional events Comprehensive speaker profiles
and speakers Archive of slides, notes and video

4. A brief history

5. Casablanca!
August 2010

6. • Aug 31st, 11:22: Launch! (1 linode)
• Aug 31st, 12:41: Unlaunch
• Aug 31st, 12:54: Read only mode
• Aug 31st, 14:15: DB server (2 linodes)
• Sep 1st: Limit 50 on dashboard
• Sep 1st: disable-dashboard setting

7. • Sep 3rd: dConstruct (and Twitter bot)
• Sep 4th: TechCrunched (read only :( )
• Sep 5th: 3 large EC2 + 1 RDS
• Sep 6th: Downgrade to 3 small EC2

8. December photo: @niqui

9. • Dec 8: Calacanis + Scoble at the same time!
• Upgrade to next size of RDS
• (Sometimes scaling vertically does the job)

10. • Jan 26th: Solr powered dashboard
• Replicated to 2, then 3 servers

11. lanyrd.com badges.lanyrd.net
Load balancer (nginx) HTTP cache (varnish)
Database
(MySQL RDS)
app server app server app server
(django/mod_wsgi) (django/mod_wsgi) (django/mod_wsgi)
search master search slave search slave Redis
(data structures +
(solr) (solr) (solr)
message queue)
logging worker worker
(MongoDB) (celery) (celery)

12. Solr + Haystack

13. apache > lucene > solr
Search the site with Solr Search
Main Wiki Powered by Lucid Imagination
Last Published: Sat, 04 Jun 2011 12:23:42 GMT
About
Welcome
Who We Are
Welcome to Solr
Documentation
PDF
Resources
What Is Solr?
Related Projects
Get Started
News
May 2011 - Solr 3.2 Released
March 2011 - Solr 3.1 Released
25 June 2010 - Solr 1.4.1 Released
7 May 2010 - Apache Lucene Eurocon 2010 Coming to Prague May 18-21
10 November 2009 - Solr 1.4 Released
20 August 2009 - Solr's first book is published!
18 August 2009 - Lucene at US ApacheCon
09 February 2009 - Lucene at ApacheCon Europe 2009 in Amsterdam
19 December 2008 - Solr Logo Contest Results
03 October 2008 - Solr Logo Contest
15 September 2008 - Solr 1.3.0 Available
28 August 2008 - Lucene/Solr at ApacheCon New Orleans
03 September 2007 - Lucene at ApacheCon Atlanta
06 June 2007: Release 1.2 available
17 January 2007: Solr graduates from Incubator
22 December 2006: Release 1.1.0 available
15 August 2006: Solr at ApacheCon US
21 April 2006: Solr at ApacheCon
21 February 2006: nightly builds
17 January 2006: Solr Joins Apache Incubator
What Is Solr?

14. More Like This
Faceting
Stored (non-indexed) fields
Highlighting
Spelling Suggestions
Boost
Find the needle you're looking for. Download Documentation
Search doesn't have to be hard. Haystack lets you write your search code Sprinting to 1.1-final
Posted on 2010/11/16 by Daniel
once and choose the search engine you want it to run on. With a familiar API Though this site has sat out of
that should make any Djangonaut feel right at home and an architecture that date, there has been a lot of
work put into Haystack 1.1. As
allows you to swap things in and out as you need to, it's how search ought of writing, there are eight issues
to be. blocking the release. I aim to
have those down to zero by the
end of the week.
Haystack is BSD licensed , plays nicely with third-party app without needing
to modify the source and supports Solr , Whoosh and Xapian . Once those eight are done, I will
be releasing 1.1-final. The RC
process really didn't do much
Get started last time and this release has
been a long time in coming. This
1. Get the most recent source. release will feature:
2. Add haystack to your INSTALLED_APPS.
3. Create search_indexes.py files for your models. Vastly improved faceting
4. Setup the main SearchIndex via autodiscover. Whoosh 1.X support!
5. Include haystack.urls to your URLconf. Document & field boost
6. Search! support

15. Model-oriented search
• Define search_indexes.py (like
admin.py) for your application
• Hook up default haystack search views
• Write a quick search.html template
• Run ./manage.py rebuild_index

17. add a conference you are signed in as simonw, do you want to sign out?
calendar conferences coverage profile
search
Search
We found 3 results for “django”
FILTER BY
django Search type
Sessions 3
Your current filters are…
TYPE: Sessions TOPIC: NoSQL PLACE: United States Clear all filters
FILTER BY
topic
NoSQL and Django Panel
EVENT DjangoCon US 2010 NoSQL 3
TIME 9th September 2010 09:00-10:00
SPEAKERS Jacob Burch Django 2
Cassandra 1
Step Away From That Database
EVENT DjangoCon US 2010
TIME 8th September 2010 11:20-12:00 FILTER BY
SPEAKERS Andrew Godwin
place
Apache Cassandra in Action United States 3
EVENT Strata 2011 Multnomah 2
TIME 1st February 2011 13:30-17:00
Oregon 2
SPEAKERS Jonathan Ellis
Portland 2
Santa Clara 1
California 1

18. class BookIndex(indexes.SearchIndex):
text = indexes.CharField(document=True, use_template=True)
speakers = indexes.MultiValueField()
topics = indexes.MultiValueField()
def prepare_speakers(self, obj):
return [a.user.t_id for a in obj.authors.exclude(
user = None
).select_related('user')]
def prepare_topics(self, obj):
return list(obj.topics.values_list('pk', flat=True))

19. search/indexes/books/
book_text.txt
{{ object.title }}
{{ object.tagline }}
{% for author in object.authors.all %}
{{ author.display_name }}
{{ author.user.t_screen_name }}
{% endfor %}
{% for topic in object.topics.all %}
{{ topic.name_en }}
{% endfor %}

20. Staying fresh
• Search engines usually don’t like accepting
writes too frequently
• RealTimeSearchIndex for low traffic sites
• ./manage.py update_index --age=6 (hours)
• Uses index.get_updated_field()
• Roll your own (message queue or similar...)

21. Replication
Solr Master
Solr Slave Solr Slave Solr Slave

22. Smarter indexing
class Article(models.Model):
needs_indexing = models.BooleanField(
default = True, db_index = True
)
...
def save(self, *args, **kwargs):
self.needs_indexing = True
super(Article, self).save(*args, **kwargs)

23. index = site.get_index(model)
updated_pks = []
objects = index.load_all_queryset().filter(
needs_indexing=True
)[:100]
if not objects:
return
for object in objects:
updated_pks.append(object.pk)
index.update_object(object)
index.load_all_queryset().filter(
pk__in = updated_pks
).update(needs_indexing = False)

24. nginx + Solr
replication trick
upstream solrmaster { server {
server 10.68.43.214:8080; listen 8983;
} location /solr/update {
upstream solrslaves { proxy_pass http://solrmaster;
server 10.68.43.214:8080; }
server 10.193.138.80:8080; location /solr/select {
server 10.204.143.106:8080; proxy_pass http://solrslaves;
} }
}

25. add a conference you are signed in as simonw, do you want to sign out?
calendar conferences coverage profile
search
Your contacts' calendar
yours 24 contacts 182
Simon
We've found 182 conferences your Twitter contacts are Willison
interested in. Your profile
page
TODAY Café Scientifique: Exploring Attend
21
the dark side of star Track
formation with the Herschel From our blog
Space Observatory Welcoming Sophie
United Kingdom / Brighton Barrett to team
21st June 2011 Lanyrd
Astronomy Science Today we have a very special
announcement (and for once,
4 contacts tracking
it's not a new feature!) We
would like to welcome the
super-wonderful Sophie Barrett
to the Lanyrd team.
21 Usability Professionals' Attend Session schedules in
Association – International Track your calendar
Conference You can now subscribe to event
schedules in your calendar of
United States / Atlanta
choice. Stay up to date at the
21st–24th June 2011 event with the schedule in the
Usability User Experience pocket where you need it.
1 contact speaking and 3 contacts tracking
Venues (and venue
maps)

26. # Original implementation
twitter_ids = [11134, 223455, 33221, ...] # fetch from Twitter
attendees = Attendee.objects.filter(
user__t_id__in = twitter_ids
).filter(
conference__start_date__gte = datetime.date.today()
)

27. # Current implementation
twitter_ids = [11134, 223455, 33221, ...] # fetch from Twitter
sqs = SearchQuerySet()
sqs = sqs.models(Conference)
or_string = ' OR '.join(twitter_ids)
sqs = sqs.narrow('attendees:(%s)' % or_string)

28. Redis

29. Commands Clients Documentation Community Download Issues
Redis is an open source, advanced key-value store. It is often What people are saying
referred to as a data structure server since keys can contain Comparison of CouchDB, Redis,
MongoDB, Casandra, Neo4J &
strings, hashes, lists, sets and sorted sets.
strings hashes lists sets others http://j.mp/l32SqM via
@DZone
Learn more →
@__NeverGiveup Oh YAY, oui tu
me redis ! *-* Hm, on s'rejoint à
Try it Download it 14h au bahut ? :o
Ready for a test drive? Check this interactive Redis 2.2.10 is the latest stable version. JE L REDIS JE FOLLOW BACK
SUR @Fuckement_TL
tutorial that will walk you through the most Interested in legacy or unstable versions?
important features of Redis. Check the downloads page. une question : "How to use
ServiceStack Redis in a web
application to take advantage of
pub / sub paradigm"
http://t.co/EOgyLU1 #redis #web
Nice - Cassandra vs MongoDB vs
CouchDB vs Redis vs Riak vs
HBase vs Membase vs Neo4j
comparison http://bit.ly/l32SqM
from @kkovacs
More...
Sponsored by
This website is open source software developed by Citrusbyte.
The Redis logo was designed by Carlos Prioglio.

30. simonw-follows:{144,21345,12328...}
europython-attendees:{344,21345,787...}
contact_ids = redis.sinter(
'simonw-follows',
'europython-attendees'
)

31. add a conference you are signed in as simonw, do you want to sign out?
Lanyrd.com
calendar conferences coverage profile
search
EuroPython 2011 You're
speaking
The European Python Conference AT THIS EVENT
19 –26 JUNE
2011
Florence
in Italy
97 attending
http://ep2011.europython.eu/ @europython PEOPLE
View the schedule on Lanyrd #europython
80 tracking
PEOPLE
Save to iCal / iPhone / Outlook / lanyrd.com/ccdpc (short URL)
GCal
TELL YOUR FRIENDS!
Tweet about this
event
119 speakers
Andreas Alan Anna
Schreiber Franzoni Ravenscroft
Topics
@onyame @franzeur
Django
Andrew Alessandro Anselm Kruis
Godwin Dentella Plone
@andrewgodwin Pyramid
Andrii Alex Martelli Antonio Cuni
@antocuni
Python
Mishkovskyi
@mishok13 Twisted
Ali Afshar Armin Rigo
Armin Edit topics

32. Celery

33. Home Download Community Documentation Code
Background Processing Distributed
Asynchronous/Synchronous Concurrency
Background Processing Distributed
Periodic Tasks Retries
Asynchronous/Synchronous Concurrency
Periodic Tasks Retries
Distributed Task Queue Celery 2.2 released!
By @asksol on 2011-02-01.
Celery is an asynchronous task queue/job queue based on distributed
message passing. It is focused on real-time operation, but supports A great number of new features,
scheduling as well. including Jython, eventlet and gevent
support. Everything is detailed in the
The execution units, called tasks, are executed concurrently on a single
Changelog, which you should have read
or more worker servers using multiprocessing, Eventlet, or gevent.
before upgrading.
Tasks can execute asynchronously (in the background) or
synchronously (wait until ready). Users of Django must also upgrade to
django-celery 2.2.
Celery is used in production systems to process millions of tasks a day.
This release would not have been
Celery is written in Python, but the protocol can be implemented in
possible without the help of
any language. It can also operate with other languages using
contributors and users, so thank you,
webhooks.
and congratulations!
The recommended message broker is RabbitMQ, but limited support
for Redis, Beanstalk, MongoDB, CouchDB, and databases (using
Celery 2.1.1 bugfix
SQLAlchemy or the Django ORM) is also available.
release
By @asksol on 2010-10-14.
Celery is easy to integrate with Django, Pylons and Flask, using the
All users are urged to upgrade. For a list
django-celery, celery-pylons and Flask-Celery add-on packages.
of changes see the Changelog.
Example Users of Django must also upgrade to
This is a simple task adding two numbers: django-celery 2.1.1.

34. Tasks?
• Anything that takes more than about 200ms
• Updating a search index
• Resizing images
• Hitting external APIs
• Generating reports

35. Trivial example
• Fetch the content of a web page
from celery.task import task
@task
def fetch_url(url):
return urllib.urlopen(url).read()
>>> result = fetch_url.delay(‘http://cnn.com/’)
>>> html = result.wait()

36. Python and MongoDB EuroPython 2011
Italy / Florence
tutorial
19th–26th June 2011
TELL YOUR FRIENDS!
Tweet about this
A session at EuroPython 2011 session
Andreas
Jung WHEN
CEO, ZOPYX Ltd Time 14:30–18:30 CET
Date 20th June 2011
MongoDB is the new star of the so-called NoSQL databases. Using
Python with MongoDB is the next logical step after having used SESSION HASH TAG
Python for years with relational databases. #sftzh
This talk will give an introduction into MongoDB and demonstrate SHORT URL
how MongoDB can be be used from Python. lanyrd.com/sftzh
More information can be found under: OFFICIAL SESSION
PAGE
http://www.zopyx.com/resources/python-mongodb-tutorial-at... ep2011.europython.eu/conf
View the schedule
More sessions at EuroPython 2011 on Python
Topics
MongoDB
Add coverage to this session Python
http://www.slideshare.net/ajung/python-mo Edit topics
A URL to coverage such as videos, slides, podcasts, handouts, sketchnotes, photos
etc. SCHEDULE
INCOMPLETE?
Add Add another session

37. Add coverage
http://www.slideshare.net/ajung/python-mongo-
dbtrainingeurop...
Link title Python and
MongoDB tutorial
Python mongo db-training-europython-2011 EuroPython 2011
Italy / Florence
19th–26th June 2011
Type of coverage
Link Audio Liveblog
Write-up Sketch notes Photos
Slides Transcript Notes
Video Handout
Coverage preview
From SlideShare:

38. The task itself...
• Tries using http://embed.ly/ to find a
preview
• Fetches the HTTP headers and first 2048
bytes
• If HTML, attempts to extract the <title>
• If other, gets the file type and size from
headers

39. Behind the scenes...
ar = enhance_link.delay(url)
poll_url = '/working/%s/' % signed.dumps({
'task_id': ar.task_id,
'on_done_url': on_done_url,
})
if 'ajax' in request.POST:
return render_json(request, {
'ok': True,
'poll_url': poll_url,
})
else:
return HttpResponseRedirect(poll_url)

40. And when it’s done...
from celery.backends import default_backend
...
task_id = request.REQUEST.get('id', '')
result = default_backend.get_result(task_id)

41. Configuration
# Carrot / Celery: queue uses Redis
CARROT_BACKEND = "ghettoq.taproot.Redis"
BROKER_HOST = " 10.11.11.11" # redis server
BROKER_PORT = 6379
BROKER_VHOST = "6"
# Task results stored in memcached, so they can
# expire automatically
CELERY_RESULT_BACKEND = "cache"
CELERY_CACHE_BACKEND =
"memcached://10.11.11.12:11211;..."

42. Tricks

43. Phantom load testing
• Deploy a new architecture on a brand new
EC2 cluster
• Leave your existing site on the old cluster
• Invisibly link to the new stack from an
<img width=1 height=1> element on your
live site (not for very long though)
• (sensible alternative: find a way to replay log files)

44. cache_version

45. add a conference you are signed in as simonw, do you want to sign out?
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Django conferences
Django
Django events looking for participants coverage
1 Django event is looking for participants
52 videos
Most recent added 3
weeks ago
ON NOW EuroPython 2011 52 slide decks
19 Most recent added 4
Italy / Florence hours ago
19th–26th June 2011
Django Plone Pyramid Python Twisted 3 audio clips
Most recent added 1
week ago
27 write-ups
SEPTEMBER DjangoCon US 2011
6 Most recent added 1
2011 United States / Portland
6th–8th September 2011
week ago
11 handouts
Django Open Source Python
Most recent added 18
hours ago
17 PyCON FR 2011 3 notes
France / Rennes Most recent added 10
17th–18th September 2011 hours ago
Django Python
By country
OCTOBER PyCon DE 2011 Ireland 1
4

46. class Conference(models.Model):
...
cache_version = models.IntegerField(default = 0)
def save(self, *args, **kwargs):
self.cache_version += 1
super(Conference, self).save(*args, **kwargs)
def touch(self):
Conference.objects.filter(pk = self.pk).update(
cache_version = F('cache_version') + 1
)

47. {% cache 36000 conf-topics conference.pk conference.cache_version %}
<ul class="tags inline-tags meta">
{% for topic in conference.topics.all %}
<li><a href="{{ topic.get_absolute_url }}">{{ topic }}</a></li>
{% endfor %}
</ul>
{% endcache %}

48. Bulk invalidation
from django.models import F
topic.conferences.all().update(
cache_version = F('cache_version') + 1
)

49. Signing

50. Pass data through an untrusted
source with confidence that it
hasn't been tampered with

51. Signing uses
• "Unsubscribe" links in emails
• lanyrd.com/un/ImN6VyI.ii0Hwm7p71DEcGfaVzziQaxeuu
?redirect_to=URL protection
Signed cookies
"You are logged in as simonw" without
hitting the database

52. Signing in Django 1.4
from django.core import signing
signing.dumps({"foo": "bar"})
signing.loads(signed_string)
response.set_signed_cookie(key, value...)
response.get_signed_cookie(key)

53. Hashed static asset
filenames in S3/CloudFront

54. global.js
global.ed81d119.js
cdn.lanyrd.net/js/global.ed81d119.js

55. Benefits
• Far futures expiry headers
• Cache-Control: max-age=315360000
• Expires: Fri, 18 Jun 2021 06:45:00 -0000 GMT
• Guaranteed updated CSS in IE
• Deploy new assets in advance of application
• Old versions stick around for rollbacks

56. ./manage.py push_static
• Minifies JavaScript and CSS
• Renames files to include sha1(contents)[:6]
• Pushes all assets to S3

57. Profiling and debugging
production systems

58. UserBasedExceptionMiddleware
from django.views.debug import technical_500_response
import sys
class UserBasedExceptionMiddleware(object):
def process_exception(self, request, exception):
if request.user.is_superuser:
return technical_500_response(request, *sys.exc_info())

59. mysql-proxy
• Very handy lua-customisable proxy for all
of your MySQL traffic
• Worst documented software ever
• log.lua - logs out ALL queries
• https://gist.github.com/1039751

60. django_instrumented
• (Unreleased) code I wrote for Lanyrd
• Collects various runtime stats about the
current request, stashes a profile JSON in
memcached
• Writes out the profile UUID as part of the
HTML
• A bookmarklet to view the profile

62. mongodb logging
• Super-fast inserts, log everything!
• Capped collections
• Structured queries
• Ask me about it in a few months

63. For the future...
• Much better profiling, monitoring and alerts
• Varnish in front of everything
• Replicated MySQL for analytics + upgrades

64. Questions?

65. Thank you!
http://lanyrd.com/sgptt