inputQueueSize metric

[Dimitris Mpanelas via user]

Regarding the inputQueueSize metric. What does it express after all? 
 Observing the inputQueueSize and inPoolUsage metrics in Prometheus, Ifound 
that when the inPoolUsage is high, the inputQueueSize is low. Thisobservation 
does not match the description of the inputQueueSize.Therefore, does this 
metric express the size of the input buffers ofeach task, or does it express 
how full the input buffers of a task are?
Thank you in advance.