DCPython: Architecture at PBS (Jun 7, 2011)
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The document details the architecture and technology stack behind PBS.org and its APIs, including the Cove API and Merlin API, highlighting their development history, design principles, and lessons learned. It outlines the use of various technologies such as Amazon Web Services, Python, Django, and database management systems to ensure scalability and efficiency. Additionally, it emphasizes the importance of community engagement through the PBS developer community, aiming to establish open development standards.
![API - Piston/Haystack/Solr
class WebObjectIndexHandler(BaseHandler):
...
def get_queryset(self):
...
return PistonSearchQuerySet().models(*models)
from haystack.query import SearchQuerySet
class PistonSearchQuerySet(SearchQuerySet):
...
def __getitem__(self, k):
...
return [IndexSerializer(i) for i in
super(PistonSearchQuerySet, self).__getitem__(k)]](https://image.slidesharecdn.com/dcpython-pbs-20110607-110608103249-phpapp02/85/DCPython-Architecture-at-PBS-Jun-7-2011-20-320.jpg)
DCPython: Architecture at PBS (Jun 7, 2011)
- 1. Architecture of PBS.org DCPython - June 7, 2011
- 2. PBS is… • PBS is a national federation of independently owned and operated public television stations and producers – Each with their own management and development resources • 1500+ highly trafficked websites: – http://www.pbs.org/ – http://www.pbs.org/nova/ – http://pbskids.org/ – http://pbskids.org/sesame/ – http://video.pbs.org/ • Enterprise services/APIs
- 3. PBS is not! • We do television dammit! • Or any of the other ~200 local stations.
- 4. What we do • Technology leadership within public broadcasting community • Distribution of national programming content • Services to local stations • Core application development. Yeah!!!
- 5. A few of our sites
- 6. History of PBS.org Early 1990’s: Hand rolled static html Late 1990’s: Hand crafted static html + CGI! Most of 2000’s: Zope/Plone CMS generated static html 2008-10: Django generated static html Launched Oct 2010: Django all the way
- 7. COVE API • Contains the metadata for all PBS videos online including pointers to streaming video • Needed to be: – Secure – Fast – Scalable
- 8. COVE API – Technology Stack • Amazon Elastic Cluster Computing (EC2) • Amazon Relational Database Service (RDS) • Linux • Python • Django • Piston for REST API
- 9. COVE API - Architecture Internet Elastic Load Balancer Auto Scale Array App Server 1 App Server N… HA Proxy RDS Master RDS Slave 1 RDS Slave 1 RDS Slave 1 App Sync Server S3 Backups
- 10. COVE API – Management Tools • Amazon Web Service Console • RightScale • Splunk
- 11. COVE API – Interesting Stuff • Easy to load test – Duplicate environment for several days • Easy to scale – Autoscale array grows automatically • Easy to upgrade – Each server built from vanilla base
- 12. COVE API – Lessons learned • Use normalized data for administration and de- normalized data for API
- 13. COVE API – Lessons learned • Piston is fine, but lacks flexibility without significant customization – TastyPie? • JSON is probably good enough • Don’t get fancy with your endpoints • Stick to REST principles • Don’t get fancy with your authentication – Use OAuth2 or simple token
- 14. PBS.org and Merlin API • PBS.org – Slim, fast layer – Pulls data from Merlin API – Uses memcache extensively – Currently Django, but could be anything (Flask?) • Merlin API – Aggregate content from distributed CMSes – Expose via standardized API – Power PBS.org and more
- 15. Merlin API – Technology stack • Python • Django • MySQL • Piston • Solr • Celery • RabbitMQ • Amazon Web Services (“cloud”) – EC2 – RDS - Relational Database Service – ELB - Elastic Load Balancing – Cloudfront CDN – S3 Storage
- 17. Merlin API architecture API Endpoint – Django Piston Search service Django-haystack Indexing service Solr Data layer – MySQL (RDS) Administration Django admin Feed ingestion Celery
- 18. Merlin API server topology Elastic Load Balancer Internet S3 backups Celery Master DB RDS Solr Index App #N App #N App #N App #n Autoscaling array
- 19. Merlin API – Management Tools • Amazon Web Service Console • RightScale • Splunk
- 20. API - Piston/Haystack/Solr class WebObjectIndexHandler(BaseHandler): ... def get_queryset(self): ... return PistonSearchQuerySet().models(*models) from haystack.query import SearchQuerySet class PistonSearchQuerySet(SearchQuerySet): ... def __getitem__(self, k): ... return [IndexSerializer(i) for i in super(PistonSearchQuerySet, self).__getitem__(k)]
- 21. Feed ingestor - Celery from celery.decorators import task, periodic_task @periodic_task(run_every=timedelta(seconds=300)) def update_webobject_states(): ... solr_visible = WebObject.children.filter(visible=True) solr_visible = solr_visible.exclude( flag__api_visible=True, available__isnull=True) ... updated = solr_visible.update(visible=False, is_indexed = False) ... signals.bulk_update.send('tasks.update_webobject_states')
- 22. Merlin API - Lessons learned • Memcached was not necessary • Denormalized search data via Solr index is much faster than querying database • Asynchronous task delegation is awesome • Celery prone to memory leaks • App server array for easy horizontal scaling – Even if not autoscaling, increase min servers • Never trust data you don’t control (validate!)
- 23. Resources • http://lucene.apache.org/solr/ • http://haystacksearch.org/ • http://celeryproject.org/ • http://celeryproject.org/docs/django-celery/ • http://aws.amazon.com/
- 24. PBS Developer Community • Dedicated to making open.PBS the industry standard in open development communities. http://open.pbs.org/ https://github.com/pbs open@pbs.org