Add size limit for link preview URLs (#30854)

app/services/fetch_link_card_service.rb

@@ -15,6 +15,9 @@ class FetchLinkCardService < BaseService
     )
   }iox
 
+  # URL size limit to safely store in PosgreSQL's unique indexes
+  BYTESIZE_LIMIT = 2692
+
   def call(status)
     @status       = status
     @original_url = parse_urls
@@ -85,7 +88,7 @@ class FetchLinkCardService < BaseService
 
   def bad_url?(uri)
     # Avoid local instance URLs and invalid URLs
-    uri.host.blank? || TagManager.instance.local_url?(uri.to_s) || !%w(http https).include?(uri.scheme)
+    uri.host.blank? || TagManager.instance.local_url?(uri.to_s) || !%w(http https).include?(uri.scheme) || uri.to_s.bytesize > BYTESIZE_LIMIT
   end
 
   def mention_link?(anchor)

spec/services/fetch_link_card_service_spec.rb

@@ -95,6 +95,19 @@ RSpec.describe FetchLinkCardService, type: :service do
         expect(a_request(:get, 'http://example.com/test?data=file.gpx%5E1')).to have_been_made.once
       end
     end
+
+    context 'with an URL too long for PostgreSQL unique indexes' do
+      let(:url) { "http://example.com/#{'a' * 2674}" }
+      let(:status) { Fabricate(:status, text: url) }
+
+      it 'does not fetch the URL' do
+        expect(a_request(:get, url)).to_not have_been_made
+      end
+
+      it 'does not create a preview card' do
+        expect(status.preview_card).to be_nil
+      end
+    end
   end
 
   context 'in a remote status' do