Ingest pipelines in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this ingest pipeline simulation?

Given the following ingest pipeline configuration and a document, what will be the value of the full_name field after processing?

Elasticsearch

{
  "description": "Combine first and last name",
  "processors": [
    {
      "set": {
        "field": "full_name",
        "value": "{{first_name}} {{last_name}}"
      }
    }
  ]
}

Document:
{
  "first_name": "Alice",
  "last_name": "Johnson"
}

A "full_name" will be "Alice"

B "full_name" will be "{{first_name}} {{last_name}}" (literal string)

C The pipeline will fail with a template error

D "full_name" will be "Alice Johnson"

💡 Hint

Remember that double curly braces {{}} are used for variable substitution in ingest pipelines.

The set processor uses mustache templates to replace variables with their values from the document. So {{first_name}} and {{last_name}} are replaced by "Alice" and "Johnson" respectively, resulting in "Alice Johnson".

❓ Predict Output

intermediate

What is the output of this pipeline with a grok processor?

Given this ingest pipeline and input document, what will be the value of the status_code field after processing?

Elasticsearch

{
  "description": "Extract status code from message",
  "processors": [
    {
      "grok": {
        "field": "message",
        "patterns": ["%{WORD:method} %{URIPATHPARAM:request} %{NUMBER:status_code:int}"]
      }
    }
  ]
}

Document:
{
  "message": "GET /home 404"
}

A 404 (as an integer)

B "404" (as a string)

C null (field not extracted)

D Pipeline fails with grok parse error

💡 Hint

The grok pattern uses :int to convert the extracted value to integer.

The grok processor extracts the status code from the message field and converts it to an integer because of the :int suffix in the pattern.

🔧 Debug

advanced

Why does this pipeline fail with a 'field not found' error?

This ingest pipeline uses a rename processor but fails with an error. What is the cause?

Elasticsearch

{
  "description": "Rename field",
  "processors": [
    {
      "rename": {
        "field": "user",
        "target_field": "username"
      }
    }
  ]
}

Document:
{
  "username": "bob123"
}

A The rename processor requires a 'copy' flag to be set to true.

B The source field 'user' does not exist in the document, causing the error.

C The pipeline syntax is invalid because 'field' and 'target_field' are swapped.

D The target field 'username' already exists, causing a conflict error.

💡 Hint

Check if the source field exists in the input document.

The rename processor tries to rename a field that does not exist in the document. Since 'user' is missing, the processor fails with a 'field not found' error.

📝 Syntax

advanced

Which option shows a valid ingest pipeline with a conditional processor?

Select the pipeline JSON that correctly uses a condition to run a processor only if the field status equals error.

A

{
  "processors": [
    {
      "set": {
        "field": "alert",
        "value": "true",
        "if": "ctx.status == 'error'"
      }
    }
  ]
}

B

{
  "processors": [
    {
      "set": {
        "field": "alert",
        "value": "true",
        "condition": "ctx.status == 'error'"
      }
    }
  ]
}

C

{
  "processors": [
    {
      "set": {
        "field": "alert",
        "value": "true"
      },
      "if": "ctx.status == 'error'"
    }
  ]
}

D

{
  "processors": [
    {
      "set": {
        "field": "alert",
        "value": "true"
      },
      "condition": "ctx.status == 'error'"
    }
  ]
}

💡 Hint

The condition must be outside the processor object, not inside the processor's parameters.

In ingest pipelines, the condition is specified as a sibling key to the processor type, not inside the processor's parameters. So 'if' is correct and placed outside the 'set' object.

🚀 Application

expert

How many processors run for this document in the pipeline?

Consider this pipeline with two processors and a condition on the second. How many processors will run when processing the document below?

Elasticsearch

{
  "processors": [
    {
      "set": {
        "field": "processed",
        "value": true
      }
    },
    {
      "remove": {
        "field": "debug"
      },
      "if": "ctx.debug == false"
    }
  ]
}

Document:
{
  "debug": true
}

A Only 1 processor runs (the set processor).

B Both processors run.

C No processors run because condition fails.

D Only the remove processor runs.

💡 Hint

Check the condition on the remove processor and the value of the debug field.

The first processor always runs and sets 'processed' to true. The second processor runs only if ctx.debug == false, but debug is true, so it does not run.