Fix 500 error caused by range much bigger then actual array

Add cr remarks

Add cr remarks

Add cr remarks

Refactor specs file

Remove obsolete new line

Remove obsolete signs

app/models/active_session.rb

@@ -146,8 +146,9 @@ class ActiveSession
     # remove sessions if there are more than ALLOWED_NUMBER_OF_ACTIVE_SESSIONS.
     sessions = active_session_entries(session_ids, user.id, redis)
     sessions.sort_by! {|session| session.updated_at }.reverse!
-    sessions = sessions[ALLOWED_NUMBER_OF_ACTIVE_SESSIONS..-1].map { |session| session.session_id }
-    destroy_sessions(redis, user, sessions)
+    sessions = sessions.drop(ALLOWED_NUMBER_OF_ACTIVE_SESSIONS)
+    sessions = sessions.map { |session| session.session_id }
+    destroy_sessions(redis, user, sessions) if sessions.any?
   end
 
   def self.cleaned_up_lookup_entries(redis, user)

spec/models/active_session_spec.rb

@@ -329,6 +329,35 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
           )
         end
       end
+
+      context 'when the number of active sessions is lower than the limit' do
+        before do
+          Gitlab::Redis::SharedState.with do |redis|
+            ((max_number_of_sessions_plus_two - 4)..max_number_of_sessions_plus_two).each do |number|
+              redis.del("session:user:gitlab:#{user.id}:#{number}")
+            end
+          end
+        end
+
+        it 'does not remove active session entries, but removes lookup entries' do
+          lookup_entries_before_cleanup = Gitlab::Redis::SharedState.with do |redis|
+            redis.smembers("session:lookup:user:gitlab:#{user.id}")
+          end
+
+          sessions_before_cleanup = Gitlab::Redis::SharedState.with do |redis|
+            redis.scan_each(match: "session:user:gitlab:#{user.id}:*").to_a
+          end
+
+          ActiveSession.cleanup(user)
+
+          Gitlab::Redis::SharedState.with do |redis|
+            lookup_entries = redis.smembers("session:lookup:user:gitlab:#{user.id}")
+            sessions = redis.scan_each(match: "session:user:gitlab:#{user.id}:*").to_a
+            expect(sessions.count).to eq(sessions_before_cleanup.count)
+            expect(lookup_entries.count).to be < lookup_entries_before_cleanup.count
+          end
+        end
+      end
     end
   end
 end