arpadboda commented on a change in pull request #489: MINIFICPP-740: Add ability to run NiFi processors from Java and Python URL: https://github.com/apache/nifi-minifi-cpp/pull/489#discussion_r260287961
########## File path: extensions/script/README.md ########## @@ -0,0 +1,64 @@ +<!-- + 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. +--> + +# Apache NiFi - MiNiFi - Python Processors Readme + + +This readme defines the configuration parameters to use ExecutePythonProcessor to run native python processors. + +## Table of Contents + +- [Description](#description) +- [Configuration](#configuration) + +## Description + +Python native processors can be updated at any time by simply adding a new processor to the directory defined in +the configuration options. The processor name, when provided to MiNiFi C++ and any C2 manifest will be that +of the name of the python script. For example, "AttributePrinter.py" will be named and referenced in the flow +as "org.apache.nifi.minifi.processors.AttributePrinter" + +Methods that are enabled within the processor are describe, onSchedule, onInitialize, and onTrigger. + +Describe is passed the a processor and is a required function. You must set the description like so: + +```python + def describe(processor): + processor.setDescription("Adds an attribute to your flow files") +``` + + + void addProperty(const std::string &name, const std::string &description, const std::string &defaultvalue, bool required, bool el) { + +onInitialize is also passed the processor reference and can be where you set properties. The first argument is the property display name, +followed by the description, and default value. The last two arguments are booleans describing if the property is required or requires EL. + +```python + def onIitialize(processor): + processor.setSupportsDynamicProperties() + processor.addProperty("property name","description","default value", True, False) +``` + Review comment: I made a previous comment here, which I don't see now, so sorry for the duplication in case that happens! Things I saw in the code and worth documenting in my opinion: -getProperty call supports getting value of dynamic properties, too. (as it's different in C++, I think it would be beneficial to have it documented) -Python processors support success and failure relationships, these are the ones the script can send to. A question: what happens in case there is a Python exception thrown in "onTrigger"? I wonder if a rollback should be triggered. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
