Pipeline testing in Elasticsearch - Step-by-Step Execution

Concept Flow - Pipeline testing

Define Pipeline

↓

Send Test Document

↓

Pipeline Processes Document

↓

Capture Output

↓

Compare Output to Expected

↓

Report Result

↓

End

The pipeline testing flow starts by defining the pipeline, sending a test document through it, capturing the output, comparing it to the expected result, and reporting pass or fail.

Execution Sample

Elasticsearch

POST _ingest/pipeline/_simulate
{
  "pipeline": {"processors": [{"set": {"field": "field1", "value": "test"}}]},
  "docs": [{"_source": {"field1": "original"}}]
}

This code simulates sending a document through a pipeline that sets 'field1' to 'test' and shows the transformed output.

Execution Table

Step	Action	Input Document	Processor Applied	Output Document	Result
1	Start simulation	{"field1": "original"}	None	{"field1": "original"}	Initial document
2	Apply set processor	{"field1": "original"}	set field1 to 'test'	{"field1": "test"}	Field updated
3	Compare output	{"field1": "test"}	N/A	{"field1": "test"}	Output matches expected
4	Report	N/A	N/A	N/A	Test Passed

💡 Pipeline simulation ends after output matches expected result.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
document	{"field1": "original"}	{"field1": "test"}	{"field1": "test"}	{"field1": "test"}

Key Moments - 2 Insights

Why does the output document change after step 2?

Because the 'set' processor modifies 'field1' from 'original' to 'test' as shown in the execution_table row 2.

What happens if the output does not match the expected result?

The test would fail at step 3, and the pipeline testing would report failure instead of pass.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'field1' after step 2?

A null

B "original"

C "test"

D "field1"

💡 Hint

Check the 'Output Document' column at step 2 in the execution_table.

At which step does the pipeline testing confirm the output matches expected?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Result' column in the execution_table where it says 'Output matches expected'.

If the 'set' processor was removed, what would happen to the test result?

A Test would fail at step 3

B Test would fail at step 2

C Test would still pass

D Test would not run

💡 Hint

Without the processor, the output document stays unchanged, so it won't match expected at step 3.

Concept Snapshot

Pipeline testing in Elasticsearch:
- Define a pipeline with processors
- Simulate sending a document through it
- Capture the output document
- Compare output to expected result
- Report pass or fail
Use _ingest/pipeline/_simulate API for testing pipelines.

Full Transcript

Pipeline testing in Elasticsearch involves defining a pipeline with processors that transform documents. We simulate sending a test document through this pipeline using the _simulate API. The pipeline processes the document step-by-step, applying each processor. After processing, we capture the output document and compare it to the expected result. If they match, the test passes; otherwise, it fails. This helps ensure pipelines work correctly before using them in production.