Elasticsearch Template


Elasticsearch Template

Opster Team

Nov 2020


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Template in Elasticsearch

What it is:

A template in Elasticsearch falls into one of the two following categories and is indexed inside Elasticsearch using its dedicated endpoint: 

  1. Index templates, which are a way to define a set of rules including index settings, mappings and an index pattern. The template is applied automatically whenever a new index is created with the matching pattern. Templates are also used to dynamically apply custom mapping for the fields which are not predefined inside existing mapping.
  2. Search templates, which help in defining templates for search queries using mustache scripting language. These templates act as a placeholder for variables defined inside the search queries.

Examples:

Create a dynamic index template:

PUT /_template/template_1?pretty
{
  "index_patterns": [
    "logs*",
    "api*"
  ],
  "settings": {
    "number_of_shards": 2
  },
  "mappings": {
    "dynamic_templates": [
      {
        "strings": {
          "match_mapping_type": "string",
          "mapping": {
            "type": "keyword"
          }
        }
      }
    ],
    "properties": {
      "host_name": {
        "type": "keyword"
      },
      "created_at": {
        "type": "date"
      }
    }
  }
}

Create a search template:

POST /_scripts/search_template_1?pretty
{
    "script": {
        "lang": "mustache",
        "source": {
            "query": {
                "match": {
                    "description": "{{query_string}}"
                }
            }
        }
    }
}

Executing a search query using search template:

GET /_search/template?pretty
{
    "id": "search_template_1", 
    "params": {
        "query_string": "hello world"
    }
}

The search request will be executed by default on all the indices available in the cluster and can be limited to particular indices using an index parameter.

Notes:

  • A dynamic index template is always useful when you do not know the field names in advance and want to control their mapping as per the business use case.

Related log errors to this ES concept


Templates are still reported as out of date after the upgrade. The template upgrade will be retried.
Templates were upgraded successfully to version
Error adding watcher template
Error loading template as part of metadata upgrading
Failed to put audit trail template
Error loading the template for the notification message index
Error loading the template for the
Adding template for index patterns
Removing template
Error updating template ; request was not acknowledged
Templates were partially upgraded to version
Error deleting template

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