Druid 0.9.0 - Merging segments using coordinator druid.coordinator.merge.on true getting warnings

Hi

I am merging druid segments using

druid.coordinator.merge.on=true

I am using default configurations everywhere else.

As it is running I am getting this WARN in overlord config a lot.

No worker selections strategy set. Using default.

How do I go about tuning my overlord config. Also we are planning to use tranquility instead of realtime. Is it possible to tell overlord to keep X worker threads exclusively for tranquility and use total - X worker threads for segment merging? Right now all the workers of middle manager are being allocated to the merge tasks. This can choke tranquility indexing which we cannot afford.

http://druid.io/docs/0.9.2/configuration/indexing-service.html