---
type: api
title: Simulate an index
description: Get the index configuration that would be applied to the specified index from an existing index template.
url: https://www.elastic.co/elastic/docs-builder/docs/4493/api/doc/elasticsearch-serverless/operation/operation-indices-simulate-index-template
resource: https://www.elastic.co/elastic/docs-builder/docs/4493/api/doc/elasticsearch-serverless/operation/operation-indices-simulate-index-template
products:
  - Elasticsearch Serverless
---

# Simulate an index

## Paths

- `POST` `/_index_template/_simulate_index/{name}`

#### Path parameters

- `name` (string) — required
  Name of the index to simulate

## Description

Get the index configuration that would be applied to the specified index from an existing index template.

## Required authorization

- Cluster privileges: `manage_index_templates`

## Authentication

- Api key: `Authorization: <value>`
  Elasticsearch APIs use key-based authentication.
  You must create an API key and use the encoded value in the request header.
  For example:
  
  
  ```
  curl -X GET "${ES_URL}/_cat/indices?v=true" \
    -H "Authorization: ApiKey ${API_KEY}"
  ```
  
  For more information about where to find API keys for the Elasticsearch endpoint (${ES_URL}) for a project, go to [Get started with Elasticsearch Serverless](https://www.elastic.co/docs/solutions/search/serverless-elasticsearch-get-started).

## Query string parameters

- `create` (boolean · default: false) — optional
  Whether the index template we optionally defined in the body should only be dry-run added if new or can also replace an existing one
- `cause` (string · default: false) — optional
  User defined reason for dry-run creating the new template for simulation purposes
- `master_timeout` (string · default: 30s) — optional
  Period to wait for a connection to the master node. If no response is received before the timeout expires, the request fails and returns an error.
- `include_defaults` (boolean · default: false) — optional
  If true, returns all relevant default configurations for the index template.

## Request body

`application/json`

- `index_patterns` (string) — required
  Array of wildcard (`*`) expressions used to match the names of data streams and indices during creation.
- `composed_of` (string[]) — required
  An ordered list of component template names.
Component templates are merged in the order specified, meaning that the last component template specified has the highest precedence.
- `template` (object) — optional
  Template to be applied.
It may optionally include an `aliases`, `mappings`, or `settings` configuration.
  - `aliases` (map string to object) — optional
    Aliases to add.
If the index template includes a `data_stream` object, these are data stream aliases.
Otherwise, these are index aliases.
Data stream aliases ignore the `index_routing`, `routing`, and `search_routing` options.
    Map values (object)
    - `filter` ({} Query) — optional
      Query used to limit documents the alias can access.
      See [Query](https://www.elastic.co/elastic/docs-builder/docs/4493/api/doc/elasticsearch-serverless/types/_types-query_dsl-querycontainer)
    - `index_routing` (string) — optional
      Value used to route indexing operations to a specific shard.
If specified, this overwrites the `routing` value for indexing operations.
    - `is_hidden` (boolean · default: false) — optional
      If `true`, the alias is hidden.
All indices for the alias must have the same `is_hidden` value.
    - `is_write_index` (boolean · default: false) — optional
      If `true`, the index is the write index for the alias.
    - `routing` (string) — optional
      Value used to route indexing and search operations to a specific shard.
    - `search_routing` (string) — optional
      Value used to route search operations to a specific shard.
If specified, this overwrites the `routing` value for search operations.
  - `mappings` (object) — optional
    Mapping for fields in the index.
If specified, this mapping can include field names, field data types, and mapping parameters.
    - `all_field` (object) — optional
      - `analyzer` (string) — required
      - `enabled` (boolean) — required
      - `omit_norms` (boolean) — required
      - `search_analyzer` (string) — required
      - `similarity` (string) — required
      - `store` (boolean) — required
      - `store_term_vector_offsets` (boolean) — required
      - `store_term_vector_payloads` (boolean) — required
      - `store_term_vector_positions` (boolean) — required
      - `store_term_vectors` (boolean) — required
    - `date_detection` (boolean) — optional
    - `dynamic` (enum) — optional
      Values: `strict`, `runtime`, `true`, `false`
    - `dynamic_date_formats` (string[]) — optional
    - `dynamic_templates` (string to object[]) — optional
    - `_field_names` (object) — optional
      - `enabled` (boolean) — required
    - `index_field` (object) — optional
      - `enabled` (boolean) — required
    - `_meta` (object) — optional
    - `numeric_detection` (boolean) — optional
    - `properties` (map string to oneOf) — optional
    - `_routing` (object) — optional
      - `required` (boolean) — required
    - `_size` (object) — optional
      - `enabled` (boolean) — required
    - `_source` (object) — optional
      - `enabled` (boolean) — optional
      - `excludes` (string[]) — optional
      - `includes` (string[]) — optional
      - `mode` (enum) — optional
        

Supported values include:
  - `disabled`
  - `stored`
  - `synthetic`: Instead of storing source documents on disk exactly as you send them,
 Elasticsearch can reconstruct source content on the fly upon retrieval.
        Values: `disabled`, `stored`, `synthetic`
    - `runtime` (map string to object) — optional
      Map values (object)
      - `fields` (map string to object) — optional
        For type `composite`
        Map values (object)
        - `type` (enum) — required
          Values: `boolean`, `composite`, `date`, `double`, `geo_point`, `geo_shape`, `ip`, `keyword`, `long`, `lookup`
      - `fetch_fields` (object[]) — optional
        For type `lookup`
        - `field` (string) — required
        - `format` (string) — optional
      - `format` (string) — optional
        A custom format for `date` type runtime fields.
      - `input_field` (string) — optional
        For type `lookup`
      - `target_field` (string) — optional
        For type `lookup`
      - `target_index` (string) — optional
        For type `lookup`
      - `script` (string) — optional
        Painless script executed at query time.
      - `on_script_error` (enum) — optional
        Values: `fail`, `continue`
      - `type` (enum) — required
        Field type, which can be: `boolean`, `composite`, `date`, `double`, `geo_point`, `ip`,`keyword`, `long`, or `lookup`.
        Values: `boolean`, `composite`, `date`, `double`, `geo_point`, `geo_shape`, `ip`, `keyword`, `long`, `lookup`
    - `enabled` (boolean) — optional
    - `subobjects` (enum) — optional
      Values: `true`, `false`
    - `_data_stream_timestamp` (object) — optional
      - `enabled` (boolean) — required
  - `settings` (object) — optional
    Configuration options for the index.
  - `lifecycle` (object) — optional
    - `data_retention` (string) — optional
      If defined, every document added to this data stream will be stored at least for this time frame.
Any time after this duration the document could be deleted.
When empty, every document in this data stream will be stored indefinitely.
    - `effective_retention` (string) — optional
      The least amount of time data should be kept by elasticsearch.
    - `retention_determined_by` (enum) — optional
      Configuration source that can influence the retention of a data stream.
      Values: `data_stream_configuration`, `default_global_retention`, `max_global_retention`, `default_failures_retention`
    - `downsampling` (object[]) — optional
      The list of downsampling rounds to execute as part of this downsampling configuration
      - `after` (string) — required
        The duration since rollover when this downsampling round should execute
      - `fixed_interval` (string) — required
        The downsample interval.
    - `downsampling_method` (enum) — optional
      The method used to downsample the data. There are two options `aggregate` and `last_value`. It requires
`downsampling` to be defined. Defaults to `aggregate`.
      Values: `aggregate`, `last_value`
    - `enabled` (boolean · default: true) — optional
      If defined, it turns data stream lifecycle on/off (`true`/`false`) for this data stream. A data stream lifecycle
that's disabled (enabled: `false`) will have no effect on the data stream.
  - `data_stream_options` (object) — optional
    - `failure_store` (object) — optional
      If defined, it specifies configuration for the failure store of this data stream.
      - `enabled` (boolean · default: true) — optional
        If defined, it turns the failure store on/off (`true`/`false`) for this data stream. A data stream failure store
that's disabled (enabled: `false`) will redirect no new failed indices to the failure store; however, it will
not remove any existing data from the failure store.
      - `lifecycle` (object) — optional
        If defined, it specifies the lifecycle configuration for the failure store of this data stream.
        - `data_retention` (string) — optional
          If defined, every document added to this data stream will be stored at least for this time frame.
Any time after this duration the document could be deleted.
When empty, every document in this data stream will be stored indefinitely.
        - `enabled` (boolean · default: true) — optional
          If defined, it turns data stream lifecycle on/off (`true`/`false`) for this data stream. A data stream lifecycle
that's disabled (enabled: `false`) will have no effect on the data stream.
- `version` (number) — optional
  Version number used to manage index templates externally.
This number is not automatically generated by Elasticsearch.
- `priority` (number) — optional
  Priority to determine index template precedence when a new data stream or index is created.
The index template with the highest priority is chosen.
If no priority is specified the template is treated as though it is of priority 0 (lowest priority).
This number is not automatically generated by Elasticsearch.
- `_meta` (object) — optional
  Optional user metadata about the index template. May have any contents.
This map is not automatically generated by Elasticsearch.
- `allow_auto_create` (boolean) — optional
- `data_stream` (object) — optional
  If this object is included, the template is used to create data streams and their backing indices.
Supports an empty object.
Data streams require a matching index template with a `data_stream` object.
  - `hidden` (boolean · default: false) — optional
    If true, the data stream is hidden.
  - `allow_custom_routing` (boolean · default: false) — optional
    If true, the data stream supports custom routing.
- `deprecated` (boolean) — optional
  Marks this index template as deprecated.
When creating or updating a non-deprecated index template that uses deprecated components,
Elasticsearch will emit a deprecation warning.
- `ignore_missing_component_templates` (string) — optional
  A list of component template names that are allowed to be absent.
- `created_date` (union) — optional
  Date and time when the index template was created. Only returned if the `human` query parameter is `true`.
- `created_date_millis` (number) — optional
  Date and time when the index template was created, in milliseconds since the epoch.
- `modified_date` (union) — optional
  Date and time when the index template was last modified. Only returned if the `human` query parameter is `true`.
- `modified_date_millis` (number) — optional
  Date and time when the index template was last modified, in milliseconds since the epoch.

## Response

`application/json`

- `overlapping` (object[])
  - `name` (string)
  - `index_patterns` (string[])
- `template` (object)
  - `aliases` (map string to object)
    Map values (object)
    - `filter` ({} Query)
      Query used to limit documents the alias can access.
      See [Query](https://www.elastic.co/elastic/docs-builder/docs/4493/api/doc/elasticsearch-serverless/types/_types-query_dsl-querycontainer)
    - `index_routing` (string)
      Value used to route indexing operations to a specific shard.
If specified, this overwrites the `routing` value for indexing operations.
    - `is_hidden` (boolean · default: false)
      If `true`, the alias is hidden.
All indices for the alias must have the same `is_hidden` value.
    - `is_write_index` (boolean · default: false)
      If `true`, the index is the write index for the alias.
    - `routing` (string)
      Value used to route indexing and search operations to a specific shard.
    - `search_routing` (string)
      Value used to route search operations to a specific shard.
If specified, this overwrites the `routing` value for search operations.
  - `mappings` (object)
    Same fields as `mappings` in `template`
  - `settings` (object)
## Code examples

#### Console

```console
POST /_index_template/_simulate_index/my-index-000001
```

#### JavaScript

```javascript
const response = await client.indices.simulateIndexTemplate({
  name: "my-index-000001",
  index_template: null,
});
```

#### Python

```python
resp = client.indices.simulate_index_template(
    name="my-index-000001",
    index_template=None,
)
```

#### curl

```curl
curl -X POST "$ELASTICSEARCH_URL/_index_template/_simulate_index/my-index-000001" \
  -H "Authorization: ApiKey $ELASTIC_API_KEY"
```

#### Java

```java
client.indices().simulateIndexTemplate(s -> s
    .name("my-index-000001")
);
```

#### PHP

```php
$resp = $client->indices()->simulateIndexTemplate([
    "name" => "my-index-000001",
]);
```

#### Ruby

```ruby
response = client.indices.simulate_index_template(
  name: "my-index-000001"
)
```

## Response examples

#### Indices simulate index template response example1

A successful response from `POST /_index_template/_simulate_index/my-index-000001`.

```json
{
  "template" : {
    "settings" : {
      "index" : {
        "number_of_shards" : "2",
        "number_of_replicas" : "0",
        "routing" : {
          "allocation" : {
            "include" : {
              "_tier_preference" : "data_content"
            }
          }
        }
      }
    },
    "mappings" : {
      "properties" : {
        "@timestamp" : {
          "type" : "date"
        }
      }
    },
    "aliases" : { }
  },
  "overlapping" : [
    {
      "name" : "template_1",
      "index_patterns" : [
        "my-index-*"
      ]
    }
  ]
}
```