Hi, I'm running v0.23 in a large cluster, and have found that the shuffle time for reduce tasks is always at least 5 seconds, even when the amount of data read by the reduce task is tiny (e.g., just 18 bytes). This shuffle time floor suggests that there's a heartbeat interval or something that has to elapse before the shuffle begins, but I can't find any sign of such a delay in the code base. Can anyone shed some light on why this is occurring?
Thanks, Kay
