Using a Python processor

Python processors in MiNiFi C++ are loaded from external files, and they keep running a function, while retaining the interpreter state. This makes them well-suited for tasks that require maintaining state between runs or executing initialization logic to be run only once. Learn how to integrate custom code seamlessly into a MiNiFi C++ agent by utilizing custom Python processors. You can unlock the full potential of your MiNiFi C++ agent by enhancing its functionality with the flexibility offered by Python processors.

The workflow of a Python processor:

At startup, the MiNiFi C++ agent reads the Python script directory specified in the minifi.properties file as the value of the nifi.python.processor.dir property. By default, this directory is set to MINIFI_HOME/minifi-python.
The agent scans the directory for compatible scripts and automatically registers them for use.
Python files are evaluated during startup. Their onSchedule function is invoked before starting a flow and their onTrigger function is called regularly as the processor is scheduled.

For more details, see the following example:

#!/usr/bin/env python
def describe(processor):
    processor.setDescription("Adds an attribute to your flow files")


def onInitialize(processor):
    processor.setSupportsDynamicProperties()


def onTrigger(context, session):
    flow_file = session.get()
    if flow_file is not None:
        flow_file.addAttribute("Python attribute", "attributevalue")
    session.transfer(flow_file, REL_SUCCESS)

To add or update processors, place the Python files in the designated script directory and restart the agent.