Resolve "Geo secondary help users not waste time on impossible operations."

app/controllers/oauth/geo_auth_controller.rb

@@ -45,11 +45,6 @@ class Oauth::GeoAuthController < ActionController::Base
   private
 
   def after_sign_in_with_gitlab(token, return_to)
-    if Gitlab::Geo.primary_node
-      primary_node = view_context.link_to('primary node', Gitlab::Geo.primary_node.url)
-      flash[:notice] = "You are on a secondary (read-only) Geo node. If you want to make any changes, you must visit the #{primary_node}.".html_safe
-    end
-
     session[:access_token] = token
     redirect_to(return_to || root_path)
   end

app/views/layouts/_page.html.haml

@@ -6,6 +6,7 @@
     .alert-wrapper
       = render "layouts/header/ee_license_banner"
       = render "layouts/broadcast"
+      = render 'layouts/header/ee/geo_secondary_banner'
       = yield :flash_message
       - unless @hide_breadcrumbs
         = render "layouts/nav/breadcrumbs"

changelogs/unreleased-ee/2524-geo-secondary-help-users-not-waste-time-on-impossible-operations.yml

+---
+title: On Secondary read-only Geo Nodes now a flash banner is shown on all pages
+merge_request: 3260
+author:
+type: added

ee/app/views/layouts/header/ee/_geo_secondary_banner.html.haml

+- if ::Gitlab::Geo.secondary? && ::Gitlab::Geo.primary_node
+  - primary_node = link_to('primary node', ::Gitlab::Geo.primary_node.url)
+  .flash-container.flash-container-page
+    .flash-notice
+      %div{ class: (container_class) }
+        %span You are on a secondary (read-only) Geo node. If you want to make any changes, you must visit the #{primary_node}.

spec/ee/spec/features/geo_node_spec.rb

+require 'spec_helper'
+
+feature 'GEO Nodes' do
+  let(:user) { create(:user) }
+  let(:project) { create(:project) }
+  let(:geo_url) { 'http://geo.example.com' }
+
+  context 'Geo Secondary Node' do
+    before do
+      allow(Gitlab::Geo).to receive(:secondary?) { true }
+      allow(Gitlab::Geo).to receive_message_chain(:primary_node, :url) { geo_url }
+
+      project.add_master(user)
+      sign_in(user)
+    end
+
+    describe "showing Flash Info Message" do
+      it 'on dashboard' do
+        visit root_dashboard_path
+        expect(page).to have_content 'You are on a secondary (read-only) Geo node.'
+      end
+
+      it 'on project overview' do
+        visit project_path(project)
+        expect(page).to have_content 'You are on a secondary (read-only) Geo node.'
+      end
+    end
+  end
+end