Component templates in Elasticsearch - Mini Project: Build & Apply

Create and Use Elasticsearch Component Templates

📖 Scenario: You are managing an Elasticsearch cluster for a company that stores logs from different applications. To keep the index settings consistent, you want to use component templates to define common settings and mappings.

🎯 Goal: Build an Elasticsearch setup where you create a component template with specific settings and mappings, then create an index template that uses this component template.

📋 What You'll Learn

Create a component template named logs_settings with number_of_shards set to 1

Add a mapping in the component template for a timestamp field of type date

Create an index template named logs_template that uses the logs_settings component template

Apply the index template to indices matching logs-*

💡 Why This Matters

🌍 Real World

Component templates help keep Elasticsearch index settings and mappings consistent across many indices, especially in logging or monitoring systems.

💼 Career

Knowing how to use component and index templates is important for Elasticsearch administrators and developers to manage scalable and maintainable data indexing.

1

Create the component template with settings

Write a PUT request to create a component template called logs_settings with number_of_shards set to 1 in the settings.

Elasticsearch

# Write the PUT request to create the component template 'logs_settings' with number_of_shards 1
# Your code here

Hint

Use the PUT _component_template/{name} API and include settings inside template.

2

Add a mapping for the timestamp field

Update the logs_settings component template to add a mappings section with a timestamp field of type date.

Elasticsearch

PUT _component_template/logs_settings
{
  "template": {
    "settings": {
      "number_of_shards": 1
    },
    # Add mappings here
  }
}
# Your code here

Hint

Inside template, add a mappings object with properties defining the timestamp field.

3

Create an index template using the component template

Write a PUT request to create an index template called logs_template that applies to index patterns matching logs-* and uses the component template logs_settings.

Elasticsearch

PUT _component_template/logs_settings
{
  "template": {
    "settings": {
      "number_of_shards": 1
    },
    "mappings": {
      "properties": {
        "timestamp": {
          "type": "date"
        }
      }
    }
  }
}

# Write the PUT request to create the index template 'logs_template' using 'logs_settings'
# Your code here

Hint

Use PUT _index_template/{name} with index_patterns and composed_of referencing the component template.

4

Verify the index template is applied

Write a GET request to retrieve the index template named logs_template and print the response.

Elasticsearch

PUT _component_template/logs_settings
{
  "template": {
    "settings": {
      "number_of_shards": 1
    },
    "mappings": {
      "properties": {
        "timestamp": {
          "type": "date"
        }
      }
    }
  }
}

PUT _index_template/logs_template
{
  "index_patterns": ["logs-*"] ,
  "composed_of": ["logs_settings"]
}

# Write the GET request to retrieve and print the 'logs_template' index template
# Your code here

Hint

Use GET _index_template/{name} to see the index template details.

Practice

1. What is the main purpose of a component template in Elasticsearch?

easy

A. To manage user access permissions

B. To store actual index data

C. To store reusable index settings and mappings

D. To perform search queries

Solution

1. Step 1: Understand component template role

   Component templates hold reusable parts like settings and mappings for indexes.

2. Step 2: Differentiate from other features

   They do not store data or handle queries or permissions directly.

3. Final Answer:

   To store reusable index settings and mappings -> Option C

4. Quick Check:

   Component templates = reusable settings/mappings [OK]

Hint: Component templates hold reusable settings, not data or queries [OK]

Common Mistakes:

• Confusing component templates with actual index data storage
• Thinking component templates handle search queries
• Assuming component templates manage user permissions

2. Which of the following is the correct way to create a component template using Elasticsearch API?

easy

A. PUT /_component_template/my_template { "template": { "settings": { "number_of_shards": 1 } } }

B. POST /my_template { "settings": { "number_of_shards": 1 } }

C. GET /_component_template/my_template { "settings": { "number_of_shards": 1 } }

D. DELETE /_component_template/my_template

Solution

1. Step 1: Identify correct HTTP method and endpoint

   Creating a component template uses PUT method on /_component_template/{name}.

2. Step 2: Check request body structure

   The body must include a template object with settings or mappings.

3. Final Answer:

   PUT /_component_template/my_template { "template": { "settings": { "number_of_shards": 1 } } } -> Option A

4. Quick Check:

   PUT + /_component_template + template body = A [OK]

Hint: Use PUT with /_component_template and include 'template' in body [OK]

Common Mistakes:

• Using POST instead of PUT for creation
• Using GET or DELETE for creating templates
• Omitting the 'template' wrapper in the JSON body

3. Given this component template creation request, what will be the value of number_of_replicas in the resulting index if used in an index template?

PUT /_component_template/replica_template
{
  "template": {
    "settings": {
      "number_of_replicas": 2
    }
  }
}

medium

A. 2

B. 1

C. 0

D. Undefined

Solution

1. Step 1: Read the component template settings

   The template sets number_of_replicas to 2 explicitly.

2. Step 2: Understand inheritance in index templates

   When this component template is used in an index template, the setting applies to the index.

3. Final Answer:

   2 -> Option A

4. Quick Check:

   Component template sets replicas = 2 [OK]

Hint: Settings in component templates apply directly when used [OK]

Common Mistakes:

• Assuming default replica count 1 overrides component template
• Thinking replicas default to 0 if not set elsewhere
• Confusing component template with index data

4. You tried to create a component template but got an error. Which of these is the most likely cause?

PUT /_component_template/my_template
{
  "settings": {
    "number_of_shards": 3
  }
}

medium

A. Using PUT instead of POST

B. number_of_shards cannot be set in component templates

C. Incorrect endpoint; should be /_index_template

D. Missing the 'template' wrapper around settings

Solution

1. Step 1: Check JSON structure for component template

   Component templates require a template key wrapping settings and mappings.

2. Step 2: Identify missing wrapper

   The request body lacks the "template" object, causing the error.

3. Final Answer:

   Missing the 'template' wrapper around settings -> Option D

4. Quick Check:

   Component template body must have 'template' key [OK]

Hint: Always wrap settings inside 'template' in component templates [OK]

Common Mistakes:

• Omitting the 'template' key in JSON body
• Confusing component template endpoint with index template
• Thinking PUT is wrong method for creation

5. You want to create an index template that uses two component templates: one for settings and one for mappings. Which is the correct way to reference both component templates in the index template?

hard

A. { "index_patterns": ["logs-*"], "template": { "settings": {}, "mappings": {} } }

B. { "index_patterns": ["logs-*"], "composed_of": ["settings_template", "mappings_template"] }

C. { "index_patterns": ["logs-*"], "components": ["settings_template", "mappings_template"] }

D. { "index_patterns": ["logs-*"], "use_components": ["settings_template", "mappings_template"] }

Solution

1. Step 1: Recall index template syntax for component templates

   Index templates use the composed_of array to list component templates.

2. Step 2: Match correct JSON structure

   { "index_patterns": ["logs-*"], "composed_of": ["settings_template", "mappings_template"] } correctly uses composed_of with component template names.

3. Final Answer:

   { "index_patterns": ["logs-*"], "composed_of": ["settings_template", "mappings_template"] } -> Option B

4. Quick Check:

   Use 'composed_of' to combine component templates [OK]

Hint: Use 'composed_of' array to combine component templates [OK]

Common Mistakes:

• Using wrong key like 'components' or 'use_components'
• Trying to put settings and mappings directly instead of referencing components
• Confusing index template syntax with component template syntax