Add ES_PRESET option to customize numbers of shards and replicas (#26483)

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>

lib/chewy/index_extensions.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Chewy
+  module IndexExtensions
+    def index_preset(base_options = {})
+      case ENV['ES_PRESET'].presence
+      when 'single_node_cluster', nil
+        base_options.merge(number_of_replicas: 0)
+      when 'small_cluster'
+        base_options.merge(number_of_replicas: 1)
+      when 'large_cluster'
+        base_options.merge(number_of_replicas: 1, number_of_shards: (base_options[:number_of_shards] || 1) * 2)
+      end
+    end
+  end
+end
+
+Chewy::Index.extend(Chewy::IndexExtensions)

lib/chewy/settings_extensions.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Chewy
+  module SettingsExtensions
+    def enabled?
+      settings[:enabled]
+    end
+  end
+end
+
+Chewy.extend(Chewy::SettingsExtensions)