Fix API elasticsearch settings update

ee/app/models/elastic/index_setting.rb

@@ -26,6 +26,19 @@ module Elastic
       def number_of_shards
         default.number_of_shards
       end
+
+      def every_alias
+        aliases.each do |alias_name|
+          yield self[alias_name]
+        end
+      end
+
+      private
+
+      def aliases
+        helper = Gitlab::Elastic::Helper.default
+        [helper.target_name] + helper.standalone_indices_proxies.map(&:index_name)
+      end
     end
   end
 end

ee/app/services/ee/application_settings/update_service.rb

@@ -51,6 +51,7 @@ module EE
       def update_elasticsearch_index_settings(number_of_replicas:, number_of_shards:)
         return if number_of_replicas.nil? && number_of_shards.nil?
 
+        if number_of_shards&.respond_to?(:to_h)
           number_of_shards.to_h.each do |index_name, shards|
             replicas = number_of_replicas[index_name]
 
@@ -61,6 +62,15 @@ module EE
               number_of_shards: shards.to_i
             )
           end
+        else
+          # This method still receives non-hash values from API
+          Elastic::IndexSetting.every_alias do |setting|
+            setting.update!(
+              number_of_replicas: number_of_replicas || setting.number_of_replicas,
+              number_of_shards: number_of_shards || setting.number_of_shards
+            )
+          end
+        end
       end
 
       private

ee/app/views/admin/application_settings/_elasticsearch_form.html.haml

@@ -80,11 +80,9 @@
                   %th= _('Number of shards')
                   %th= _('Number of replicas')
               %tbody
-                - aliases = [elastic_helper.target_name] + elastic_helper.standalone_indices_proxies.map(&:index_name)
-                - aliases.each do |alias_name|
+                - Elastic::IndexSetting.every_alias do |setting|
                   %tr
-                    - setting = Elastic::IndexSetting[alias_name]
-                    %td= alias_name
+                    %td= setting.alias_name
                     %td
                       = f.number_field :elasticsearch_shards, name: "application_setting[elasticsearch_shards][#{setting.alias_name}]", value: setting.number_of_shards, class: 'form-control gl-form-input', id: "application_setting_elasticsearch_shards[#{setting.alias_name}]"
                     %td

ee/changelogs/unreleased/329669-fix-update-elasticsearch-settings-by-api.yml

+---
+title: Fix API elasticsearch settings update
+merge_request: 60740
+author:
+type: fixed

ee/spec/services/application_settings/update_service_spec.rb

@@ -170,6 +170,31 @@ RSpec.describe ApplicationSettings::UpdateService do
             end
           end
         end
+
+        context 'setting number_of_shards and number_of_replicas' do
+          let(:alias_name) { 'alias-name' }
+
+          it 'accepts hash values' do
+            opts = { elasticsearch_shards: { alias_name => 10 }, elasticsearch_replicas: { alias_name => 2 } }
+
+            described_class.new(setting, user, opts).execute
+
+            setting = Elastic::IndexSetting[alias_name]
+            expect(setting.number_of_shards).to eq(10)
+            expect(setting.number_of_replicas).to eq(2)
+          end
+
+          it 'accepts legacy (integer) values' do
+            opts = { elasticsearch_shards: 32, elasticsearch_replicas: 3 }
+
+            described_class.new(setting, user, opts).execute
+
+            Elastic::IndexSetting.every_alias do |setting|
+              expect(setting.number_of_shards).to eq(32)
+              expect(setting.number_of_replicas).to eq(3)
+            end
+          end
+        end
       end
     end