Puppet users - Apr 2014 - Referencing a value from one level to another.

Puppeteers,

I'm trying to get something done in puppet/hiera, and I'm curious if
it's
possible. A bit of background:

We're using puppet and hiera to build out and maintain Apache Solr, and 
we're using Solr in a cloud structure. What this ends up meaning 
configuration-wise is that we have our data broken off into shards, and 
servers that are hosting different replicas of the shards for redundancy. 
For a simplified sense, say it looks like this...

Server1 hosts:
  shard1, replica 1
  shard2, replica 1

Server2 hosts:
  shard1, replica 2
  shard2, replica 2

Server3 hosts:
  shard3, replica 1
  shard4, replica 1

...and so on. So each shard exists on multiple hosts, each host has 
multiple shards, but not every shard is on every host. 

We were able to handle this just fine by using a hiera array to list the 
shards at the _host_.yaml level. No big deal. Done and done, works great in 
production.


The issue that has come up is that some of the shards (which are JVMs) have 
grown a bit and require a heap size greater than the default. Obviously 
this would be something we'd want to wrangle with puppet and hiera.
We've
come up with some initial attempts that seem to work, which involve just 
enhancing the hiera data when we declare the shards at a host level. So 
instead of:

Server1.yaml::
shards:
- shard1
- shard2

We have something like this:

Server1.yaml::
shards:
- shard1: 5G
- shard2: 7G

...which is workable. The thing I don't like about it is that I'm
defining
the heap size at the host level, even though they should be consistent for 
any given shard across servers. This is redundant at best, and leaves 
things open for inconsistency across servers at worst. I kind of want to 
raise the heap size declarations up above the host level, up to the 
application or environment level I guess. But I would still need to declare 
which shards are where at the host level. In short, I guess I need the 
deployment to look for what shards should be on a host at the host level, 
and then look up the chain a bit to see what heap size that shard should 
have. 

Does this sound doable?

Thanks in advance, 
Jim

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