Ping handler during initial wamup

[Ere Maijala]

As far as I can see, when a Solr instance is started (whether standalone 
or SolrCloud), a PingRequestHandler will wait until index warmup is 
complete before returning (at least with useColdSearcher=false) which 
may take a while. This poses a problem in that a load balancer either 
needs to wait for the result or employ a short timeout for timely 
failover. Of course the request is eventually served, but it would be 
better to be able to switch over to another server until warmup is complete.

So, is it possible to configure a ping handler to return quickly with 
non-OK status if a search handler is not yet available? This would allow 
the load balancer to quickly fail over to another server. I couldn't 
find anything like this in the docs, but I'm still hopeful.

I'm aware of the possibility of using a health state file, but I'd 
rather have a way of doing this automatically.

--Ere