NiFi for data flow automation in Hadoop - Step-by-Step Execution

Concept Flow - NiFi for data flow automation

Start: Data Source

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NiFi Ingest Processor

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Data Flow Controller

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Routing & Transformation Processors

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Data Destination

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Monitoring & Logging

Data flows from source through NiFi processors that ingest, route, transform, and deliver data automatically.

Execution Sample

Hadoop

GenerateFlowFile -> LogAttribute -> UpdateAttribute -> PutFile

This NiFi flow creates a file, logs its attributes, updates attributes, then saves the file to disk.

Execution Table

Step	Processor	Action	Input	Output	Notes
1	GenerateFlowFile	Create flow file	None	FlowFile with content	Starts data flow with a file
2	LogAttribute	Log attributes	FlowFile	FlowFile unchanged	Attributes logged for monitoring
3	UpdateAttribute	Modify attributes	FlowFile	FlowFile with updated attributes	Adds or changes metadata
4	PutFile	Write file to disk	FlowFile	File saved	Data delivered to destination
5	End	Flow complete	None	None	No more processors, flow ends

💡 Flow ends after PutFile processor writes data to disk

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
FlowFile Content	None	Created	Unchanged	Unchanged	Saved to disk
FlowFile Attributes	{}	Default set	Logged	{"updated": true}	{"updated": true}

Key Moments - 3 Insights

Why does the FlowFile content stay unchanged after LogAttribute?

LogAttribute only reads and logs metadata; it does not modify the FlowFile content as shown in step 2 of the execution_table.

How does UpdateAttribute affect the FlowFile?

UpdateAttribute changes the FlowFile's metadata attributes but does not alter the actual content, as seen in step 3 of the execution_table.

What causes the data flow to end?

The flow ends after PutFile writes the FlowFile content to disk, completing the data delivery, as noted in step 4 and the exit_note.

Visual Quiz - 3 Questions

Look at the execution_table, what is the state of FlowFile content after step 2?

A Deleted

B Created and unchanged

C Modified by LogAttribute

D Empty

💡 Hint

Refer to the 'Output' column in step 2 of execution_table showing 'FlowFile unchanged'

At which step does the FlowFile attributes get updated?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Check the 'Action' and 'Notes' columns in step 3 of execution_table

If PutFile fails, what happens to the data flow according to the table?

A Flow stops without saving data

B Flow continues to next processor

C Flow ends successfully

D Flow restarts from GenerateFlowFile

💡 Hint

Exit note says flow ends after PutFile writes data; failure means no save and no next step

Concept Snapshot

NiFi automates data flow by connecting processors.
Each processor performs a task: ingest, log, update, or deliver data.
FlowFiles carry data and metadata through processors.
Processors run in sequence until data reaches destination.
Failures stop flow or trigger retries.
Visualize flow as steps from source to sink.

Full Transcript

NiFi automates data flow by moving data through connected processors. It starts with a data source, then processors like GenerateFlowFile create data. LogAttribute reads metadata without changing content. UpdateAttribute modifies metadata. PutFile saves data to disk. The flow ends after data is saved. Variables like FlowFile content and attributes change step-by-step. Beginners often wonder why some processors don't change content; this is because some only log or update metadata. The flow stops after the last processor completes its task. Understanding each step helps visualize how NiFi manages data automatically.