Alter default shard count in index templates

Currently, we use only a single primary shard for each beat index,
as configured by the index templates. This is not usually an optimal
setup, as all index searching is handled on a single node. A more
efficient configuration for a small number of different indices is
to balance, with around one primary shard per node. This
commit exposes the config option to set the number of primary shards,
which was previously hardcoded to 1. This now defaults to one shard
per data node in the cluster.

Change-Id: Icacf76c2270c98f8676d57952c00773646ca7b51

elk_metrics_7x/roles/elastic_data_hosts/defaults/main.yml

@@ -34,6 +34,9 @@ elastic_data_interface: "{{ ansible_default_ipv4['alias'] }}"
 ## Elasticsearch index template settings
 # Set the default max number of fields used in a query
 # elastic_max_docvalue_fields_search: "100"
+# Set the number of primary shards for each index
+# (defaults to the number of Elasticsearch data nodes)
+# elastic_primary_shard_count: 1
 
 # The set of nodes used for elasticsearch discovery
 # elasticsearch_discovery_seed_hosts: "{{ (elastic_hosts | union(groups['kibana'])) | map('extract', hostvars, 'ansible_host') | list }}"

elk_metrics_7x/roles/elastic_data_hosts/vars/data-node-variables.yml

@@ -169,6 +169,7 @@ elasticsearch_number_of_replicas: "{{ ((data_nodes | length) > 2) | ternary('2',
 elasticsearch_beat_settings:
   number_of_replicas: "{{ elasticsearch_number_of_replicas }}"
   max_docvalue_fields_search: "{{ elastic_max_docvalue_fields_search | default('100') }}"
+  shard_count: "{{ elastic_primary_shard_count | default(elasticsearch_data_node_details | length) }}"
 
 # Shuffled elasticsearch endpoints (with localhost if relevant) for use in beat config files
 elasticsearch_data_hosts: |-

elk_metrics_7x/templates/_macros.j2

@@ -281,7 +281,7 @@ setup.template.fields: "${path.config}/fields.yml"
 # Overwrite existing template
 setup.template.overwrite: {{ host == data_nodes[0] | default(false)}}
 
-{% set shards = 1 %}
+{% set shards = elasticsearch_beat_settings.shard_count | int %}
 
 # Elasticsearch template settings
 setup.template.settings: