The core concepts of NiFi

NiFi's fundamental design concepts closely relate to the main ideas of Flow Based Programming (FBP). Here are some of the main NiFi concepts and how they map to FBP:


NiFi Term	FBP Term	Description
FlowFile	Information Packet	A FlowFile represents each object moving through the system and for each one, NiFi keeps track of a map of key/value pair attribute strings and its associated content of zero or more bytes.
FlowFile Processor	Black Box	Processors actually perform the work. In EIP terms a processor is doing some combination of data routing, transformation, or mediation between systems. Processors have access to attributes of a given FlowFile and its content stream. Processors can operate on zero or more FlowFiles in a given unit of work and either commit that work or rollback.
Connection	Bounded Buffer	Connections provide the actual linkage between processors. These act as queues and allow various processes to interact at differing rates. These queues can be prioritized dynamically and can have upper bounds on load, which enable back pressure.
Flow Controller	Scheduler	The Flow Controller maintains the knowledge of how processes connect and manages the threads and allocations thereof which all processes use. The Flow Controller acts as the broker facilitating the exchange of FlowFiles between processors.
Process Group	subnet	A Process Group is a specific set of processes and their connections, which can receive data via input ports and send data out via output ports. In this manner, process groups allow creation of entirely new components simply by composition of other components.

This design model, also similar to SEDA, provides many beneficial consequences that help NiFi to be a very effective platform for building powerful and scalable dataflows. A few of these benefits include:

Lends well to visual creation and management of directed graphs of processors
Is inherently asynchronous which allows for very high throughput and natural buffering even as processing and flow rates fluctuate
Provides a highly concurrent model without a developer having to worry about the typical complexities of concurrency
Promotes the development of cohesive and loosely coupled components which can then be reused in other contexts and promotes testable units
The resource constrained connections make critical functions such as back-pressure and pressure release very natural and intuitive
Error handling becomes as natural as the happy-path rather than a coarse grained catch-all
The points at which data enters and exits the system as well as how it flows through are well understood and easily tracked