* Fixed an issue where dynamic update to minimum_master_nodes settings would not take immediate effect
* Added LocalNodeMasterListener support to the ClusterService. Enables listening to when the local node becomes/stopped being a master
A Bulk UDP service is a service listening over UDP for bulk format requests. The idea is to provide a low latency UDP service that allows to easily index data that is not of critical nature.
The Bulk UDP service is disabled by default, but can be enabled by setting `bulk.udp.enabled` to `true`.
The bulk UDP service performs intenral bulk aggregation of the data and then flushes it based on several parametres:
* `bulk.udp.bulk_actions`: The number of actions to flush a bulk after, defaults to `1000`.
* `bulk.udp.bulk_size`: The size of the current bulk request to flush the request once exceeded, defaults to `5mb`.
* `bulk.udp.flush_interval`: An interval after which the current request is flushed, regarldess of the above limits. Defaults to `5s`.
* `bulk.udp.concurrent_requests`: The number on max in flight bulk requests allowed. Defaults to `4`.
The network settings allowed are:
* `bulk.udp.host`: The host to bind to, defualts to `network.host` which defaults to any.
* `bulk.udp.port`: The port to use, defaults to `9700-9800`.
Here is an example of how it can be used:
> cat bulk.txt
{ "index" : { "_index" : "test", "_type" : "type1" } }
{ "field1" : "value1" }
{ "index" : { "_index" : "test", "_type" : "type1" } }
{ "field1" : "value1" }
> cat bulk.txt | nc -w 0 -u localhost 9700
the index.shard.recovery.concurrent_streams controls how many streams are opened from a recovery source to a recovery target to transfer index files. Reduce it from 5 to 3 to reduce the load when doing recovery (for example, due to relocation).
Note, recent changes in network buffering will mean that recovery will progress considerably faster, so this change will not affect recovery times.
Streamline the use of minimum should match to all relevant queries to accept `minimum_should_match`, and allow all relevant queries to accept the advanced "string" based config
