ES: provide default version for class-level write operations

After project is converted to allow multiple schemas,
operations such as `delete_index!` will require version,
so provide a default version for now.

ee/lib/gitlab/elastic/helper.rb

@@ -4,8 +4,7 @@ module Gitlab
   module Elastic
     class Helper
       # rubocop: disable CodeReuse/ActiveRecord
-      def self.create_empty_index
-        index_name = Project.index_name
+      def self.create_empty_index(version = ::Elastic::MultiVersionUtil::TARGET_VERSION)
         settings = {}
         mappings = {}
 
@@ -23,7 +22,9 @@ module Gitlab
           mappings.deep_merge!(klass.__elasticsearch__.mappings.to_hash)
         end
 
-        client = Project.__elasticsearch__.client
+        proxy = Project.__elasticsearch__.version(version)
+        client = proxy.client
+        index_name = proxy.index_name
 
         # ES5.6 needs a setting enabled to support JOIN datatypes that ES6 does not support...
         if Gitlab::VersionInfo.parse(client.info['version']['number']) < Gitlab::VersionInfo.new(6)
@@ -42,16 +43,16 @@ module Gitlab
       end
       # rubocop: enable CodeReuse/ActiveRecord
 
-      def self.delete_index
-        Project.__elasticsearch__.delete_index!
+      def self.delete_index(version = ::Elastic::MultiVersionUtil::TARGET_VERSION)
+        Project.__elasticsearch__.version(version).delete_index!
       end
 
       def self.refresh_index
         Project.__elasticsearch__.refresh_index!
       end
 
-      def self.index_size
-        Project.__elasticsearch__.client.indices.stats['indices'][Project.__elasticsearch__.index_name]['total']
+      def self.index_size(version = ::Elastic::MultiVersionUtil::TARGET_VERSION)
+        Project.__elasticsearch__.version(version).client.indices.stats['indices'][Project.__elasticsearch__.index_name]['total']
       end
     end
   end

ee/lib/tasks/gitlab/elastic/test.rake

@@ -4,7 +4,7 @@ namespace :gitlab do
       desc 'GitLab | Elasticsearch | Test | Measure space taken by ES indices'
       task index_size: :environment do
         puts "===== Size stats for index: #{Project.__elasticsearch__.index_name} ====="
-        pp Gitlab::Elastic::Helper.index_size.slice(*%w(docs store))
+        pp Gitlab::Elastic::Helper.index_size(::Elastic::MultiVersionUtil::TARGET_VERSION).slice(*%w(docs store))
       end
 
       desc 'GitLab | Elasticsearch | Test | Measure space taken by ES indices, reindex, and measure space taken again'