Strip whitespace from Sentry URL

Adding extra whitespace in the DSN could prevent the server from
starting due to InvalidURIErrors in sentry-raven.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/49621

app/models/application_setting.rb

@@ -219,6 +219,7 @@ class ApplicationSetting < ActiveRecord::Base
   validate :terms_exist, if: :enforce_terms?
 
   before_validation :ensure_uuid!
+  before_validation :strip_sentry_values
 
   before_save :ensure_runners_registration_token
   before_save :ensure_health_check_access_token
@@ -382,6 +383,11 @@ class ApplicationSetting < ActiveRecord::Base
     super(levels.map { |level| Gitlab::VisibilityLevel.level_value(level) })
   end
 
+  def strip_sentry_values
+    sentry_dsn.strip! if sentry_dsn.present?
+    clientside_sentry_dsn.strip! if clientside_sentry_dsn.present?
+  end
+
   def performance_bar_allowed_group
     Group.find_by_id(performance_bar_allowed_group_id)
   end

changelogs/unreleased/sh-strip-sentry-dsn.yml

+---
+title: Strip whitespace from Sentry URL
+merge_request: 21703
+author:
+type: fixed

spec/models/application_setting_spec.rb

@@ -305,6 +305,36 @@ describe ApplicationSetting do
     end
   end
 
+  describe 'setting Sentry DSNs' do
+    context 'server DSN' do
+      it 'strips leading and trailing whitespace' do
+        subject.update(sentry_dsn: ' http://test ')
+
+        expect(subject.sentry_dsn).to eq('http://test')
+      end
+
+      it 'handles nil values' do
+        subject.update(sentry_dsn: nil)
+
+        expect(subject.sentry_dsn).to be_nil
+      end
+    end
+
+    context 'client-side DSN' do
+      it 'strips leading and trailing whitespace' do
+        subject.update(clientside_sentry_dsn: ' http://test ')
+
+        expect(subject.clientside_sentry_dsn).to eq('http://test')
+      end
+
+      it 'handles nil values' do
+        subject.update(clientside_sentry_dsn: nil)
+
+        expect(subject.clientside_sentry_dsn).to be_nil
+      end
+    end
+  end
+
   describe '#disabled_oauth_sign_in_sources=' do
     before do
       allow(Devise).to receive(:omniauth_providers).and_return([:github])