HI Jian He,
I have checked below code in RMAppManager.createAndPopulateNewRMApp. With this piece of code, even if priority is NOT set in submissionContext, we will set it with a default priority for any apps (with 0 priority in dflt case). This will not impact any apps untill we enable app priority from top level.
Priority appPriority = rmContext.getScheduler()
This same code is invoked from recoverApplication also. So even in rolling upgrade cases where app is saved to Store w/o priority in submission context, it will be added wth a priority 0 with above piece of code during recovery. Jian He will this be fine? or do you see some other problem because of this. pls share your feedback.