Compare and Swap added to Google App Engine Cloud

On Wednesday Google released v1.5.3 of their App Engine cloud platform SDK, the release notes are here. There are some interesting new additions to the API, however the one that really caught our eye is the addition of a Compare and Swap (CAS) primitive to their Memcache API.

A CAS primitive can be used to build all sorts of higher level synchronisation primitives like mutexes etc. and so the existence of such a primitive may be very handy for synchronisation of GAE taskqueue tasks! The SDK is currently quite lacking in such synchronisation tools so it will be interesting what can be done with this new addition.