@mburgess I have the same problem. The code was written in jython.   from org.apache.commons.io import IOUtils from java.nio.charset import StandardCharsets from org.apache.nifi.processor.io import OutputStreamCallback from java.lang import Object # Define a subclass of OutputStreamCallback for use in session.write() class PyOutputStreamCallback(OutputStreamCallback):   def __init__(self, cadena):     self.cadena = cadena   def process(self, outputStream):     outputStream.write(bytearray(self.cadena.encode('utf-8'))) # end class flowFile = session.get() if (flowFile != None):     table = flowFile.getAttribute('table_name')         if (table != 'database_1.dbo.dtproperties'):         newFlowFile = session.create(flowFile)         newFFC = ''         newFlowFile = session.write(newFlowFile, PyOutputStreamCallback(newFFC))                 session.transfer(newFlowFile, REL_SUCCESS)             elif (table == 'database_1.dbo.dtproperties'):         session.remove(flowFile)     else:         session.transfer(flowFile, REL_FAILURE)   I'm understanding that flow files are passing one by one, right? So if there is a flow file with an attribute ''database_1.dbo.dtproperties" should be eliminated without affecting other flow files. But I got "flowfile has already marked for removal" ... View more