Create idea of read-only database

In GitLab EE, a GitLab instance can be read-only (e.g. when it's a Geo
secondary node). But in GitLab CE it also might be useful to have the
"read-only" idea around. So port it back to GitLab CE.

Also having the principle of read-only in GitLab CE would hopefully
lead to less errors introduced, doing write operations when there
aren't allowed for read-only calls.

Closes gitlab-org/gitlab-ce#37534.

3 files changed, 15 insertions, 5 deletions

diff --git a/app/models/concerns/cache_markdown_field.rb b/app/models/concerns/cache_markdown_field.rb
index 193e459977a..9417033d1f6 100644
--- a/app/models/concerns/cache_markdown_field.rb
+++ b/app/models/concerns/cache_markdown_field.rb
@@ -59,7 +59,7 @@ module CacheMarkdownField
 
   # Update every column in a row if any one is invalidated, as we only store
   # one version per row
-  def refresh_markdown_cache!(do_update: false)
+  def refresh_markdown_cache
     options = { skip_project_check: skip_project_check? }
 
     updates = cached_markdown_fields.markdown_fields.map do |markdown_field|
@@ -71,8 +71,14 @@ module CacheMarkdownField
     updates['cached_markdown_version'] = CacheMarkdownField::CACHE_VERSION
 
     updates.each {|html_field, data| write_attribute(html_field, data) }
+  end
+
+  def refresh_markdown_cache!
+    updates = refresh_markdown_cache
+
+    return unless persisted? && Gitlab::Database.read_write?
 
-    update_columns(updates) if persisted? && do_update
+    update_columns(updates)
   end
 
   def cached_html_up_to_date?(markdown_field)
@@ -124,8 +130,8 @@ module CacheMarkdownField
     end
 
     # Using before_update here conflicts with elasticsearch-model somehow
-    before_create :refresh_markdown_cache!, if: :invalidated_markdown_cache?
-    before_update :refresh_markdown_cache!, if: :invalidated_markdown_cache?
+    before_create :refresh_markdown_cache, if: :invalidated_markdown_cache?
+    before_update :refresh_markdown_cache, if: :invalidated_markdown_cache?
   end
 
   class_methods do
diff --git a/app/models/concerns/routable.rb b/app/models/concerns/routable.rb
index 12e93be2104..22fde2eb134 100644
--- a/app/models/concerns/routable.rb
+++ b/app/models/concerns/routable.rb
@@ -156,6 +156,8 @@ module Routable
   end
 
   def update_route
+    return if Gitlab::Database.read_only?
+
     prepare_route
     route.save
   end
diff --git a/app/models/concerns/token_authenticatable.rb b/app/models/concerns/token_authenticatable.rb
index a7d5de48c66..ec3543f7053 100644
--- a/app/models/concerns/token_authenticatable.rb
+++ b/app/models/concerns/token_authenticatable.rb
@@ -43,15 +43,17 @@ module TokenAuthenticatable
         write_attribute(token_field, token) if token
       end
 
+      # Returns a token, but only saves when the database is in read & write mode
       define_method("ensure_#{token_field}!") do
         send("reset_#{token_field}!") if read_attribute(token_field).blank? # rubocop:disable GitlabSecurity/PublicSend
 
         read_attribute(token_field)
       end
 
+      # Resets the token, but only saves when the database is in read & write mode
       define_method("reset_#{token_field}!") do
         write_new_token(token_field)
-        save!
+        save! if Gitlab::Database.read_write?
       end
     end
   end