FEATURE: report on admin dashboard when favicon is failing to load

app/controllers/static_controller.rb

@@ -106,7 +106,8 @@ class StaticController < ApplicationController
         file.unlink
         data
       rescue => e
-        Rails.logger.warn("Invalid favicon_url #{SiteSetting.favicon_url}: #{e}\n#{e.backtrace}")
+        AdminDashboardData.add_problem_message('dashboard.bad_favicon_url', 1800)
+        Rails.logger.debug("Invalid favicon_url #{SiteSetting.favicon_url}: #{e}\n#{e.backtrace}")
         ""
       end
     end

app/models/admin_dashboard_data.rb

@@ -37,7 +37,7 @@ class AdminDashboardData
     @problem_syms.push(*syms) if syms
     @problem_blocks << blk if blk
   end
-  class << self; attr_reader :problem_syms, :problem_blocks; end
+  class << self; attr_reader :problem_syms, :problem_blocks, :problem_messages; end
 
   def problems
     problems = []
@@ -47,6 +47,9 @@ class AdminDashboardData
     AdminDashboardData.problem_blocks.each do |blk|
       problems << instance_exec(&blk)
     end
+    AdminDashboardData.problem_messages.each do |i18n_key|
+      problems << AdminDashboardData.problem_message_check(i18n_key)
+    end
     problems.compact
   end
 
@@ -54,6 +57,7 @@ class AdminDashboardData
   def self.reset_problem_checks
     @problem_syms = []
     @problem_blocks = []
+    @problem_messages = ['dashboard.bad_favicon_url']
 
     add_problem_check :rails_env_check, :ruby_version_check, :host_names_check,
                       :gc_checks, :ram_check, :google_oauth2_config_check,
@@ -83,6 +87,26 @@ class AdminDashboardData
     AdminDashboardData.new.problems
   end
 
+  def self.problem_message_check(i18n_key)
+    $redis.get(problem_message_key(i18n_key)) ? I18n.t(i18n_key) : nil
+  end
+
+  def self.add_problem_message(i18n_key, expire_seconds=nil)
+    if expire_seconds.to_i > 0
+      $redis.setex problem_message_key(i18n_key), expire_seconds.to_i, 1
+    else
+      $redis.set problem_message_key(i18n_key), 1
+    end
+  end
+
+  def self.clear_problem_message(i18n_key)
+    $redis.del problem_message_key(i18n_key)
+  end
+
+  def self.problem_message_key(i18n_key)
+    "admin-problem:#{i18n_key}"
+  end
+
   def as_json(_options = nil)
     @json ||= {
       global_reports: AdminDashboardData.reports(GLOBAL_REPORTS),

config/locales/server.en.yml

@@ -790,6 +790,7 @@ en:
     email_polling_errored_recently:
       one: "Email polling has generated an error in the past 24 hours. Look at <a href='/logs' target='_blank'>the logs</a> for more details."
       other: "Email polling has generated %{count} errors in the past 24 hours. Look at <a href='/logs' target='_blank'>the logs</a> for more details."
+    bad_favicon_url: "The favicon is failing to load. Check your favicon_url setting in <a href='/admin/site_settings'>Site Settings</a>."
 
   site_settings:
     censored_words: "Words that will be automatically replaced with &#9632;&#9632;&#9632;&#9632;"

spec/models/admin_dashboard_data_spec.rb

@@ -278,4 +278,26 @@ describe AdminDashboardData do
     include_examples 'stats cachable'
   end
 
+  describe '#problem_message_check' do
+    let(:key) { AdminDashboardData.problem_messages.first }
+
+    before do
+      described_class.clear_problem_message(key)
+    end
+
+    it 'returns nil if message has not been added' do
+      expect(described_class.problem_message_check(key)).to be_nil
+    end
+
+    it 'returns a message if it was added' do
+      described_class.add_problem_message(key)
+      expect(described_class.problem_message_check(key)).to eq(I18n.t(key))
+    end
+
+    it 'returns a message if it was added with an expiry' do
+      described_class.add_problem_message(key, 300)
+      expect(described_class.problem_message_check(key)).to eq(I18n.t(key))
+    end
+  end
+
 end