Friday, June 06, 2008

Google App Engine limitations and workarounds

One of the current limitations of the Google App Engine is the lack of scheduled background processes. But early adapters are creative to circumnavigate this and other limitations. The most simple solution to this problem has William Vambenepe: he uses Google Reader to subscribe to a dummy RSS feed on his App Engine hosted test app, that results in some kind of regular polling with an interval of about 30 minutes. Of course this can't be used for any serious stuff, and the eight seconds maximum lifespan of a request also is not helping much to improve the situation. William concludes:
In the meantime, this was a fun exploration of the GAE environment. It makes it clear to me that this environment is still a toy. But a very interesting and promising one.
A more sophisticated but also much more complicated solution to the same problem has Peter Dolan: HTTPMR, a Map Reduce implementation in Python for running on HTTP based web clusters such as Google App Engine.

I am experimenting myself with a completely rewritten, not yet released version of ErlyComet, for adding a RESTful, highly scalable Comet layer with transactional cache in front of Google App Engine (or any other service which provides easy, cheap, reliable and scalable solution for persistence and shortlived HTTP requests)

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