peferron commented on issue #6993: [Proposal] Dynamic prioritization and laning
URL: 
https://github.com/apache/incubator-druid/issues/6993#issuecomment-461159982
 
 
   > I was thinking a period threshold is likely to align with how people often 
set up historical tiers: a 'hot' tier for the latest 30 days and a 'cold' tier 
for older data.
   
   Got it. It makes sense if the goal is to be an alternative to tiering in 
certain situations, as you mentioned in your proposal.
   
   Some of the confusion, I think, is coming from the fact that the proposal 
matches "light" with "high priority", and "heavy" with "low priority", but then 
goes on to propose a period threshold that's intuitively not the best way to 
achieve that: heavy queries hitting recent data will remain high priority, 
while light queries hitting older data will be adjusted down to low priority.
   
   That's why the comments went on to suggest thresholds that are intuitively 
better correlated, such as duration or segment count (and we could keep going 
until we end up applying ML to it).
   
   Let me ask you this: if there was an omniscient function available in the 
broker that could exactly predict how light or heavy a query is going to be, 
would you remove the period threshold, or leave it in as an optional 
configuration option?
   
   If you remove it, then this proposal is indeed about classifying light vs 
heavy queries.
   
   If you leave it in, then this proposal is rather about letting users 
dynamically adjust priorities based on abitrary criteria, with light or heavy 
just being one of them; and it's OK to sometimes classify a heavy query as 
high-priority and vice-versa.
   
   I hope this doesn't sound like nitpicking—it would be helpful (at least to 
me) to clear this up.
   
   BTW, my suggestion of a duration threshold was only as a review comment—in 
our case, we fully control the query priority and don't have any need for 
dynamic prioritization, so laning is the only useful feature for us here. My 
selfish interest would even be to ship laning first and push dynamic 
prioritization to a follow-up PR. 😛 
   

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