chenboat commented on issue #4626: Low level realtime consumer (LLC) got into 
ERROR state due to thread race condition.
URL: 
https://github.com/apache/incubator-pinot/issues/4626#issuecomment-534276264
 
 
   Thanks @mcvsubbu for the replies.
   > Do you have a feel of why we were waiting so long for the semaphore? The 
number of parallel builds allowed can be increased. I wonder what value you 
have it set to.
   
    Our max.parallel.segment.builds is set to 2. Since the affected table runs 
on a busy shared tenant, the value seems to be too low? 
    
   > How many consuming segments do you have in the same host? Are you building 
large segments? Is it time to spread these partitions around?
   
   The number of consuming segments depends on the number of realtime table 
partitions assigned to the host, right? This could be in the range of a few 
dozens. We also think big segment size makes the problem worse and the first 
temporary fix I did was to lower the segment flush threshold from 5 hrs to 0.5 
hrs. That mitigated the issue. 
   
   > I am wondering if there will be performance issues anyway due to too many 
segments being present in the same host.
   So far from the ERROR state issue, the shared tenant seems to be fine in 
terms of ingestion and query performance. Our alert system did not fire 
additional alerts.
   
   

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