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From Vinayak Borkar <vinay...@gmail.com>
Subject Helix Resource Config guarantees
Date Wed, 08 May 2013 16:04:53 GMT

I have a fundamental question about guarantees in Helix regarding newly 
added resources and their configuration.

When I add a new resource into Helix, I need to first configure it by 
setting some properties using the ConfigAccessor. AFAICT Helix does not 
provide a way to do both the steps (add the resource and configure it) 
in one atomic step. Another thing I noticed is that addition of a new 
Resource into Helix even in AUTO_REBALANCE mode does not immediately 
trigger a External State computation. Instead I seem to need to call 
rebalance on that resource. Since I need the configuration set before 
state models at the nodes start manipulating the resource, this is 
perfect. It allows me to add a resource, configure it and then call 
rebalance so the state models do not see an unconfigured resource.

My question is if this is a guarantee provided by Helix? i.e. Is 
rebalancing of a new resource triggered ONLY by an explicit rebalance call?

I have read/heard of a rebalance timer. How do I set that value and does 
that impact rebalancing of new resources?


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