anchor.diff:  curl -XPUT localhost:9200/_cluster/settings -d '{
       "transient" : {
           "cluster.routing.allocation.exclude._ip" : "10.0.0.1"
  -    } 
  -}' 
  ---------------------------------------------------
  +    }
  +}'
  +--------------------------------------------------
  
positive.code: The following settings may be used:
  
  `cluster.routing.allocation.allow_rebalance`::
          Allow to control when rebalancing will happen based on the total 
          state of all the indices shards in the cluster. `always`, 
          `indices_primaries_active`, and `indices_all_active` are allowed, 
          defaulting to `indices_all_active` to reduce chatter during 
          initial recovery.
  
  
  `cluster.routing.allocation.cluster_concurrent_rebalance`::
        Allow to control how many concurrent rebalancing of shards are 
        allowed cluster wide, and default it to `2`.
  
  
  `cluster.routing.allocation.node_initial_primaries_recoveries`::
         Allow to control specifically the number of initial recoveries 
         of primaries that are allowed per node. Since most times local 
         gateway is used, those should be fast and we can handle more of 
         those per node without creating load.
  
  
  `cluster.routing.allocation.node_concurrent_recoveries`::
       How many concurrent recoveries are allowed to happen on a node. 
       Defaults to `2`.
  
  added[1.0.0.RC1]
  
  `cluster.routing.allocation.enable`::
      Controls shard allocation for all indices, by allowing specific
      kinds of shard to be allocated. Can be set to:
      * `all` (default) - Allows shard allocation for all kinds of shards.
      * `primaries` - Allows shard allocation only for primary shards.
      * `new_primaries` - Allows shard allocation only for primary shards for new indices.
      * `none` - No shard allocations of any kind are allowed for all indices.
  
  `cluster.routing.allocation.disable_new_allocation`::
         Allows to disable new primary allocations. Note, this will prevent 
         allocations for newly created indices. This setting really make 
         sense when dynamically updating it using the cluster update 
         settings API. This setting has been deprecated in favour
         for `cluster.routing.allocation.enable`.
  
  
  `cluster.routing.allocation.disable_allocation`::
          Allows to disable either primary or replica allocation (does not 
          apply to newly created primaries, see `disable_new_allocation` 
          above). Note, a replica will still be promoted to primary if 
          one does not exist. This setting really make sense when 
          dynamically updating it using the cluster update settings API.
          This setting has been deprecated in favour for `cluster.routing.allocation.enable`.
  
  
  `cluster.routing.allocation.disable_replica_allocation`::
        Allows to disable only replica allocation. Similar to the previous 
        setting, mainly make sense when using it dynamically using the 
        cluster update settings API. This setting has been deprecated in
        favour for `cluster.routing.allocation.enable`.
  
  `cluster.routing.allocation.same_shard.host`::
        Prevents that multiple instances of the same shard are allocated
        on a single host. Defaults to `false`. This setting only applies 
        if multiple nodes are started on the same machine.
  
  `indices.recovery.concurrent_streams`::
         The number of streams to open (on a *node* level) to recover a 
         shard from a peer shard. Defaults to `3`. 
  
  [float]
  [[allocation-awareness]]
  
negative.code: [source,js]
  --------------------------------------------------
  curl -XPUT localhost:9200/test/_settings -d '{
        "index.routing.allocation.exclude.tag" : "value3"
  }'
  --------------------------------------------------
  
  `index.routing.allocation.require.*` can be used to
  specify a number of rules, all of which MUST match in order for a shard
  to be  allocated to a node. This is in contrast to `include` which will
  include a node if ANY rule matches.
  