publish subscribe - How to implement a light pub-sub service on App Engine? -

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during google i/o 2009 "offline processing on app engine: ahead" presentation (video, slides), brett slatkin presents task queue service.

he states

pub-sub systems maximize transactions, decoupling:

  • large numbers of small transactions per second
  • one-to-many fan-out changing receivers
  • guaranteed ordering, filtering, two-phase commit

and emphasises

our new api implements queueing, not pub-sub

i'm interested in subset of functionalities:

  • one-to-many fan-out changing selected/fixed internal receiver handlers
  • guaranteed ordering, filtering, two-phase commit

targeted goal ease publishing of notifications/messages between different modules of same web application. sample usage scenarios cases be:

  • making payment module aware of receivals of bills.
  • making user able track changes of particular domain object has decided follow/star.

what correct way implement these on top of task queue service ?

consider using cloud pub/sub. it's externalized version of internal pub/sub technology, has been used extensively within google 7 years , proven scalable , robust. of today it's still beta, we're going ga (in few months).


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