Handle unreachable ES host in settings check

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

@@ -3,7 +3,7 @@
 - recreate_index_url = help_page_url('integration/elasticsearch.md')
 - recreate_index_link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: recreate_index_url }
 - recreate_index_text = _("Changes won't take place until the index is %{link_start}recreated%{link_end}.").html_safe % { link_start: recreate_index_link_start, link_end: '</a>'.html_safe }
-- elasticsearch_available = Gitlab::Elastic::Helper.default.client.ping
+- elasticsearch_available = Gitlab::Elastic::Helper.default.ping?
 
 %section.settings.expanded.as-elasticsearch.no-animate#js-elasticsearch-settings{ data: { qa_selector: 'elasticsearch_tab' } }
   .settings-header

ee/changelogs/unreleased/299991-opening-admin-settings-page-results-in-the-error-500-if-localho.yml

+---
+title: Handle network unreachable for ES settings check
+merge_request: 52586
+author:
+type: fixed

ee/lib/gitlab/elastic/helper.rb

@@ -294,6 +294,13 @@ module Gitlab
         end
       end
 
+      # handles unreachable hosts and any other exceptions that may be raised
+      def ping?
+        client.ping
+      rescue
+        false
+      end
+
       private
 
       def additional_index_options

ee/spec/lib/ee/gitlab/elastic/helper_spec.rb

@@ -359,4 +359,15 @@ RSpec.describe Gitlab::Elastic::Helper do
       end
     end
   end
+
+  describe '#ping?' do
+    subject { helper.ping? }
+
+    it 'does not raise any exception' do
+      allow(Gitlab::Elastic::Helper.default.client).to receive(:ping).and_raise(StandardError)
+
+      expect(subject).to be_falsey
+      expect { subject }.not_to raise_exception
+    end
+  end
 end

ee/spec/views/admin/application_settings/_elasticsearch_form.html.haml_spec.rb

@@ -218,5 +218,18 @@ RSpec.describe 'admin/application_settings/_elasticsearch_form' do
         expect(rendered).to include('Retry migration')
       end
     end
+
+    context 'when elasticsearch is unreachable' do
+      before do
+        allow(Gitlab::Elastic::Helper.default).to receive(:ping?).and_return(false)
+      end
+
+      it 'does not show the retry migration card' do
+        render
+
+        expect(rendered).not_to include('There is a halted Elasticsearch migration')
+        expect(rendered).not_to include('Retry migration')
+      end
+    end
   end
 end