Random Musings About Google App Engine

CHIRP Radio

• www.chirpradio.org
  • Broadcasts sweet music 21 hours a day
  • Non-profit, volunteer run
• Needed admin-y apps for DJs
  • Playlist Tracker
  • Traffic Log
  • Music Library
• I know, we'll use App Engine!

Compact, Convenient

• One directory of files
• appcfg.py update .
• zip your 3rd party modules
• one cross platform SDK
• some perks at http://localhost:8000/_ah/
• nice dashboard at http://appspot.com/

Task Queue is Badass

taskqueue.add(url='/worker',
              params={'key': key})

• Submit an asynchronous task
• Retries on errors

Datastore Needs More Abstraction

• SomeObject.get(key)
• It times out a lot
  • our app: 0.2 requests / 1s
  • timeouts: 5 times a day
  • these requests use 4x more CPU quota
• We wrote AutoRetry()
  • this is stupid
• put/delete is addressed in Python API
• googleappengine issue #674

Can't peak under the hood

• example: Resolver404 Error
• Triggered by random exception raised on import
• Lasts for 1-2 min
• googleappengine issue #1409
  • closed as WontFix

Kiss of Death

Error: Server Error

Kiss of Death

Error: Server Error

• happens once every couple days?
• not in the logs, no exception to catch
• googleappengine issue #2022

CHIRP Code

http://code.google.com/p/chirpradio/