Apache Nifi — Data Ingestion Tool

8 min readSep 27, 2021

Apache Nifi — is a data flow management system that comes along with a UI tool that will be easy to handle. It’s a data logistics platform that automates the transfer of data between different systems. Since it provides real-time control it is easy to manage the movement of data between any source and destination. It is configurable plumbing for moving data around, similar to how “Fedex”, “UPS” or other courier delivery services move parcels around. Similar to those devices, Apache NIFI can track the data in real-time.

How NIFI works :

It consists of atomic elements that can be combined into groups to build a data flow
Processors

-NIFI has more than 280+ processors
- Every processor has its responsibility

For example

-Get file processors to read a file from the source
- Put file processors write a file to the destination
- It fetches data from various data sources and writes the data into various data sources
- The data source can be anything it can be SQL databases such as Postgres, Oracle, MySQL or no SQL database like MongoDB, couch base or it can also be search engine -solr or elastic search, cache server — HBase, Redis it can also connect to Kafka messaging queue, aws entities like stree buckets and dynamo DB
- NIFI has many processors to serve the requirement. we can also write our custom processors

Flow File
- NIFI propagates data in the form of a flow file
-It can contain any form of data — “CSV, JSON, XML, text or even a binary data”
- NIFI can propagate any form of data from any source to any destination since it has a flow file abstraction
- We can use the processor to process the flow file to generate a new flow file as a result
Connection
- All Processors together connected to create a data flow called connections which act as a queue for flow files
Process Group
- We can create the processor groups by connecting one or more processors which will help in complex data flow for better maintenance
Controller Service
- It is a shared service that processors can use
- For example — the processor which gets and puts data to the SQL database can have a controller service with the required DB connection details

Flow File :

Has Data
Composed of two components
- Content — data itself
- Attribute — It’s metadata from the flow file which resembles Key-value pairs
The processor can manipulate the flow file attribute — “ update, add, remove attributes “ or it can change the content of the flow file or it can do both
Lifecycle
- Persisted in the disk
- Passed — by — reference
- Whenever a new flow file is generated by the processor it immediately gets persisted in the disk and nifi will just pass the reference of the flow file to the next processor
- Ingesting the new data into the existing flow file or changing the content of the existing flow file will generate a new flow file
- It won’t be created by just manipulating the attributes of the flow file
Types of Processors
- ( https://www.nifi.rocks/apache-nifi-processors/ )
- Nifi has 280+ processors (increases in each release )
- It can distribute data to many systems
- Some of them are

Data Ingestion Processors — Ingest data from a various data source

Data Transformation Processors- Transforms the data to various formats according to the requirements

Data Egress/sending data Processors — Send the processed data to various types of destination systems

Routing And Mediation Processors — Helps us to conditionally change the way how a flow file to be processed

Database Access Processors — Commonly used processors to access the database

Attribute Extraction Processors — Help us to extract and manipulate the attribute of the flow file from its content or other existing attributes or both. Usually, it is provided with the right set of attributes which can be used with routing and mediation processors

System Interaction Processors -Supports us to run OS-specific commands specified by the user and writes the output of the command to the flow file

Splitting and Aggregation Processors — Split and aggregate data according to our requirement

HTTP and UDP Processors — NIFI can ingest and send data using HTTP and UDP protocol

Amazon Web Services Processors — Can communicate with AWS entities

Processor configuration and connection relationship

Standard configuration
- Common across all processors
Unique Configuration
- Unique for specific processors
Relationships
- Each processor has zero or more relationships defined for it
- Once the processor has finished processing it routes one or more flow files to their relationships
- Its flow file is responsible for handling these relationships by creating the connection for each of them to another processor. u can also terminate the relationship when not in use
- NIFI will complain if we have any unhandled relationship in the processor we can’t start the processor until we handle it

So apart from this, it has a concept of Backpressure and data provenance.

Backpressure :

In NIFI each processor will take their own time to process based on the complexity involved
To handle this NIFI has a backpressure configuration each connection can have its backpressure defined
- Object threshold
- Size threshold
NIFI stops the processor if either of the thresholds is reached

Data provenance :

Here It logs all the information occurring on the ingested data flow. so it’s possible to search the event information from UI, Data is accessible for all the Nifi levels and processor levels

The correct place to use :

For Hadoop data ingestion

Data egress for Hadoop to other destination

Data movement outside Hadoop within the data center — “NON-ETL FLOWS”

What I Have Done

As a part of my POC I used NIFI to ingest streaming data from Apache Kafka to hive instead of the storm :

Need for NIFI:

Apache NiFi is a fantastic tool for transforming data into the format, structure, and content you’ll need for further analysis and processing. You may create processors that can achieve this flow file or use the existing processors in many cases, and you can even use the ExecuteScript processors to build scripts on the fly to change the data.

My Work :

Processors and configuration:

Flow 1:

Consume kafka — -> Extract Text — -> convert Attributes to CSV — -> convert CSV to Avro — -> convert avro to orc — -> puthdfs

Challenges faced:

Hive table should be created in such a way that it stores data in orc format and it works

Flow 2 :

Consume kafka — ->Update Attribute — -> Extract Text — -> convert Attributes to CSV — -> Update Record — ->Partition Record — -> convert avro to orc — -> puthdfs

Processor configuration:
consume Kafka configuration

UpdateAttribute Configurations:

Configure the processor as I have shown below

Next, I Added the schema. name attribute to the flow file so that I can use this name in my AvroSchemaRegistry and use the same AvroSchemaRegistry for the Record Reader/Writer controller services.

3.UpdateRecord Configs:

Record Reader:

Our input data is in CSV format so configure the CSV reader controller service as shown below.

If my incoming data has a header then I can define it as a header property and set that to true or we have to define the scheme in the registry later. The “ schema access strategy “ uses the string fields from the header. So using these two we can generate schema dynamically.

Record Writer:

As a next step convert the CSV format data into Avro using the Using “, Next store the orc files to hdfs using “ Convert Avro to orc “ processor

The schema should look like below

Here I’m allowing all the values including null, in your case you can exclude null by keeping the type as string/integer.
So the processor will route the flow file data content to failure status [“relationship”]

Add new property in the update record processor as shown in the below image