I am not able to clear the connection queue in Nifi. The only change i made to the PutJMS processor was to change the URL to failover:(address)?randomize=false. The message just stopped in the queue and did not proceed to PutJMS. I stopped all the processors after sometime in the hope that I will change the config again for further testing. But since the queue is not empty and it is not allowing me to change the config in PutJMS processor.
PS: I am trying to send messages to IBM MQ using PutJMS.
If you would like to investigate this further, you can get a NiFi thread dump and look for the "putJMS" related threads to see what those threads are waiting on.
# ./nifi.sh dump <dump-file-name>
Unfortunately right now there is no way to interrupt/kill these threads from within NiFi's UI. NiFi will be adding that ability in a future release. For now, as Saikrishna mentioned, a NiFi restart will be required to kill these threads if they never complete on their own.
Check if you can close the connection from IBM MQ, that should trigger the processing of Flow Files again.