reverse_flow_file_content.py

#
#  Licensed to the Apache Software Foundation (ASF) under one or more
#  contributor license agreements.  See the NOTICE file distributed with
#  this work for additional information regarding copyright ownership.
#  The ASF licenses this file to You under the Apache License, Version 2.0
#  (the "License"); you may not use this file except in compliance with
#  the License.  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.
#

import codecs
import time


class ReadCallback:
    def process(self, input_stream):
        self.content = codecs.getreader('utf-8')(input_stream).read()
        return len(self.content)


class WriteReverseStringCallback:
    def __init__(self, content):
        self.content = content

    def process(self, output_stream):
        reversed_content = self.content[::-1]
        output_stream.write(reversed_content.encode('utf-8'))
        return len(reversed_content)


def onTrigger(context, session):
    flow_file = session.get()
    if flow_file is not None:
        read_callback = ReadCallback()
        session.read(flow_file, read_callback)
        session.write(flow_file, WriteReverseStringCallback(read_callback.content))
        flow_file.addAttribute('python_timestamp', str(int(time.time())))
        session.transfer(flow_file, REL_SUCCESS)