Matching service use consistent hash decide which queue is assigned to which server. Most of time, the server will poll task from cache instead of persistent database.
If I add a new matching service, All cache in queue will be re-consistent-hash to new places, and this will cause all old cache outdated. Will it cause any problem?
Most of the time tasks are not cached but matched immediately to a waiting long poll. We call it a sync match. So adding a matching service shouldn't affect the health of the running applications.