@Lanic - With release of Apache NiFi 1.7 and HDF 3.2 in mid 2018, the ability in terminate threads still executing on a processor that is in a state of "stopping" is now possible. After changing state of processor from start to stop, you will see processor display red square. You should give the running threads an opportunity to complete their execution. If it appears the processor is just not going to stop (hung threads) you can right click on the processor and select "Terminate" from the context menu displayed as follows: ... View more