FrankChen021 commented on issue #19937:
URL: https://github.com/apache/druid/issues/19937#issuecomment-5226417013

   > A ShardedPrioritizedExecutorService composite holding N ordinary 
PrioritizedExecutorService instances; it delegates per-task work
   (execute/submit) to a random shard and fans out lifecycle calls.
   
   I think this proposal changes the scheduling semantics of the processing 
pool significantly.
   
   Today, all queued tasks share one priority queue, so priority ordering is 
global within the process. With the proposed sharding, priority ordering would 
become local to each shard. As a result, a lower-priority task could start 
while a higher-priority task is waiting in another shard.
   
   Similarly, when druid.processing.fifo=true and two queued tasks have the 
same priority, they are currently dequeued in global FIFO order. With sharding, 
FIFO ordering would apply only within each shard, so a later task in one shard 
could be dequeued before an earlier task in another.
   
   We should each an agreement on such semantic changes before discussing more 
about the proposal.


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