This document discusses extending the functionality of Apache NiFi through custom processors and controller services. It provides an overview of the NiFi architecture and repositories, describes how to create extensions with minimal dependencies using Maven archetypes, and notes that most extensions can be developed within hours. Quick prototyping of data flows is possible using existing binaries, applications, and scripting languages. Resources for the NiFi developer guide and example Maven projects are also listed.

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Mission to NARs with
Apache NiFi
Aldrin Piri - @aldrinpiri
ApacheCon Big Data 2016
12 May 2016

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Tutorial Resources
https://github.com/apiri/nifi-mission-to-nars-workshop

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Agenda
• Start with a dataflow… but we can do better!
• Do better with the NiFi Framework and custom processor
• Extension Points: Processors, Controller Services, Reporting Tasks
• Process Session & Process Context
• How the API ties to the NiFi repositories
• Testing isn’t that bad!
• Share with templates!

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Adding new functionality and development approach
 Extending the platform is about leveraging expansive Java ecosystem and existing code
– Make use of open source projects and provided libraries for targeted systems and services
– Reuse existing, proprietary or closed source libraries and wrap their functionality in the framework
 Test framework provides powerful means of testing extensions in isolation as they
would work in a live instance
 Deployment is as simple as copying the created NAR to your instance(s) lib directory

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Minimal Dependencies Needed
 Java Development Kit, version 1.7 or later
 Maven, version 3.1.0+

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Boilerplate Code is provided via Maven Archetype
 Support for creating bundles of major extension points of Processors and Controller
Services
– Processor Bundle
– Controller Service Bundle

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What is a NAR?
– Bundles the developed code to provide
extensions and their dependencies
– Allows extension classloader isolation,
aiding in versioning issues that can be
pervasive in interacting with a wide variety
of systems, services, and formats
NAR == NiFi ARchive
Consider it to be an OSGi-lite package
NAR Bundle Structure

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How long does it take to create an extension?
 Incorporating functionality from an existing library
– Create a bundle
– Include a dependency to the library
– Design User Experience
• Properties – How can this extension be configured? What are valid values for user input?
• Relationships – How will data move to the next stage of its processing?
– Wrap the core classes of the library in the framework and implement onTrigger
• ProcessSession abstracts interactions with backing repositories and handles unit-of-work sessions
• ProcessContext allows accessing defined properties which the framework has validated
– Test
– Deploy
For the majority of cases, development time is measured in hours*

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How long does it really take to create an extension?
 Increased development effort may be needed for handling specific protocols
– Driven through manual management of sessions, when there are resources with their own
lifecycles beyond the sole onTrigger method
– Common for protocol “Listeners”
For the majority of cases, development time is still measured in hours

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Behind the Scenes

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Architecture

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NiFi Architecture – Repositories - Pass by reference
FlowFile Content Provenance
F1 C1 C1 P1 F1
BEFORE
AFTER
F2 C1 C1 P3 F2 – Clone (F1)
F1 C1 P2 F1 – Route
P1 F1 – Create

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NiFi Architecture – Repositories – Copy on Write
FlowFile Content Provenance
F1 C1 C1 P1 F1 - CREATE
BEFORE
AFTER
F1 C1
F1.1 C2 C2 (encrypted)
C1 (plaintext)
P2 F1.1 - MODIFY
P1 F1 - CREATE

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Quick (and dirty?) Prototyping

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Prototype Dataflows Using Existing Binaries/Applications
 ExecuteProcess – Acts as a source
processor, creating FlowFiles containing
data written to STDOUT by the target
application
 ExecuteStreamCommand – Provides
content of FlowFiles to an external
application via STDIN and creates
FlowFiles containing data written STDOUT
Processors allow making external calls to applications and programs outside of the JVM

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Increased Flexibility of Prototyping via Scripting Languages
 ExecuteScript– Acts as a source processor,
creating FlowFiles containing data from a
referenced Script
 InvokeScriptedProcessor – Provides access
to the core framework API for interacting
with NiFi like a native Java processor
Processors allow using JVM friendly interpreted languages

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Resources
Developer Guide
– http://nifi.apache.org/developer-guide.html
Apache NiFi Maven Archetypes
– https://cwiki.apache.org/confluence/display/NIFI/Maven+Proj
ects+for+Extensions
Mission to NARs with Apache NiFi sample bundle
– https://github.com/apiri/nifi-mission-to-nars-workshop

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Thanks for hanging out!