Simulate index templates
You can use the Simulate Index Template API to preview how index templates will be applied to an index or simulate an index template before creating it.
Endpoints
POST /_index_template/_simulate
POST /_index_template/_simulate/<template_name>
POST /_index_template/_simulate_index/<index_name>
Path parameters
The following table lists the available path parameters.
| Parameter | Data type | Description |
|---|---|---|
template_name | String | The name of the index template to simulate. |
index_name | String | The name of the index to use for simulating template resolution. |
Request body fields
The following table lists the available request body fields.
| Field | Data type | Description |
|---|---|---|
index_patterns | Array | The index patterns to which the template applies. |
template | Object | The template definition. |
template.settings | Object | The index settings to apply. |
template.mappings | Object | The field mappings to apply. |
template.aliases | Object | The aliases to apply. |
priority | Integer | The template’s priority value, used to determine which template is applied when multiple templates match an index. Higher values take precedence. |
version | Integer | The template version. |
_meta | Object | Metadata for the template. |
Example request: Simulate a template
Use the following request to simulate a template without creating it:
POST /_index_template/_simulate
{
"index_patterns": ["log-*"],
"template": {
"settings": {
"number_of_shards": 1
},
"mappings": {
"properties": {
"message": {
"type": "text"
}
}
}
},
"priority": 5
}
Example request: Simulate a named template
You can simulate a specific template by specifying the name of the template.
First, create a template named template_for_simulation using the following request:
PUT /_index_template/template_for_simulation
{
"index_patterns": ["logs-sim-*"],
"template": {
"settings": {
"number_of_shards": 1,
"number_of_replicas": 1
},
"mappings": {
"properties": {
"timestamp": {
"type": "date"
},
"message": {
"type": "text"
},
"level": {
"type": "keyword"
}
}
}
},
"priority": 10,
"version": 1,
"_meta": {
"description": "Template used for simulation example",
"owner": "Docs Team"
}
}
You can now simulate the template named template_for_simulation:
POST /_index_template/_simulate/template_for_simulation
Example request: Simulate a template on a specific index
Simulating a template on a specific index name is particularly useful for resolving conflicts or debugging priority issues among templates. The following request demonstrates how all applicable templates, with overlapping index patterns, will be applied to an index named logs-sim-1:
POST /_index_template/_simulate_index/logs-sim-1
Example response
{
"template": {
"settings": {
"index": {
"number_of_shards": "1",
"number_of_replicas": "1"
}
},
"mappings": {
"properties": {
"level": {
"type": "keyword"
},
"message": {
"type": "text"
},
"timestamp": {
"type": "date"
}
}
},
"aliases": {}
},
"overlapping": []
}
Response body fields
| Field | Data type | Description |
|---|---|---|
template | Object | The template applied. |
template.settings | Object | The resolved index settings. |
template.mappings | Object | The resolved field mappings. |
template.aliases | Object | The resolved aliases. |
overlapping | Array | A list of other index templates that match the same index pattern but were not applied. |
Required permissions
If you are using the Security plugin, make sure you have the appropriate permissions: indices:admin/index_template/simulate.