On 07/03/2014 10:13 PM, Mike Spreitzer wrote:

I do think the issue these address --- the need to get application logic
involved in, e.g., shutdown --- is most of what an application needs;
involvement in selection of which member(s) to delete is much less
important (provided that clean shutdown mechanism prevents concurrent

I assume this is more of the whole "cattle" model, where an instance could disappear at any time so applications should design for that?

As an alternate viewpoint, if a particular instance in a group is working on something "expensive" (long-running, difficult to checkpoint, etc.), maybe it would make sense to allow the application to help make the decision on which instance to shut down (or possibly even veto/delay the scale down operation). If it takes a minute to finish the operation, and 15 minutes to redo it on another instance...


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