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Index templates |
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Index templates let you initialize new indexes with predefined mappings and settings. For example, if you continuously index log data, you can define an index template so that all of these indexes have the same number of shards and replicas.
To create an index template, use a PUT or POST request:
PUT _index_template/<template name>
POST _index_template/<template name>
This command creates a template named daily_logs
and applies it to any new index whose name matches the pattern logs-2020-01-*
and also adds it to the my_logs
alias:
PUT _index_template/daily_logs
{
"index_patterns": [
"logs-2020-01-*"
],
"template": {
"aliases": {
"my_logs": {}
},
"settings": {
"number_of_shards": 2,
"number_of_replicas": 1
},
"mappings": {
"properties": {
"timestamp": {
"type": "date",
"format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"
},
"value": {
"type": "double"
}
}
}
}
}
You should see the following response:
{
"acknowledged": true
}
If you create an index named logs-2020-01-01
, you can see that it has the mappings and settings from the template:
PUT logs-2020-01-01
GET logs-2020-01-01
{
"logs-2020-01-01": {
"aliases": {
"my_logs": {}
},
"mappings": {
"properties": {
"timestamp": {
"type": "date",
"format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"
},
"value": {
"type": "double"
}
}
},
"settings": {
"index": {
"creation_date": "1578107970779",
"number_of_shards": "2",
"number_of_replicas": "1",
"uuid": "U1vMDMOHSAuS2IzPcPHpOA",
"version": {
"created": "7010199"
},
"provided_name": "logs-2020-01-01"
}
}
}
}
Any additional indexes that match this pattern---logs-2020-01-02
, logs-2020-01-03
, and so on---will inherit the same mappings and settings.
Index patterns cannot contain any of the following characters: :
, "
, +
, /
, \
, |
, ?
, #
, >
, and <
.
To list all index templates:
GET _cat/templates
GET /_index_template
To find a template by its name:
GET _index_template/daily_logs
To get a list of all templates that match a pattern:
GET _index_template/daily*
To check if a specific template exists:
HEAD _index_template/<name>
You can create multiple index templates for your indexes. If the index name matches more than one template, OpenSearch takes the mappings and settings from the template with the highest priority and applies it to the index.
For example, say you have the following two templates that both match the logs-2020-01-02
index and there’s a conflict in the number_of_shards
field:
PUT _index_template/template-01
{
"index_patterns": [
"logs*"
],
"priority": 0,
"template": {
"settings": {
"number_of_shards": 2,
"number_of_replicas": 2
}
}
}
PUT _index_template/template-02
{
"index_patterns": [
"logs-2020-01-*"
],
"priority": 1,
"template": {
"settings": {
"number_of_shards": 3
}
}
}
Because template-02
has a higher priority
value, it takes precedence over template-01
. The logs-2020-01-02
index would have the number_of_shards
value as 3 and the number_of_replicas
as the default value 1.
You can delete an index template using its name:
DELETE _index_template/daily_logs
Managing multiple index templates has the following challenges:
- If you have duplication between index templates, storing these index templates results in a bigger cluster state.
- If you want to make a change across all your index templates, you have to manually make the change for each template.
You can use composable index templates to overcome these challenges. Composable index templates let you abstract common settings, mappings, and aliases into a reusable building block called a component template.
You can combine component templates to compose an index template.
Settings and mappings that you specify directly in the create index request override any settings or mappings specified in an index template and its component templates. {: .note }
Let's define two component templates---component_template_1
and component_template_2
:
PUT _component_template/component_template_1
{
"template": {
"mappings": {
"properties": {
"@timestamp": {
"type": "date"
}
}
}
}
}
PUT _component_template/component_template_2
{
"template": {
"mappings": {
"properties": {
"ip_address": {
"type": "ip"
}
}
}
}
}
When creating index templates, you need to include the component templates in a composed_of
list.
OpenSearch applies the component templates in the order in which you specify them within the index template. The settings, mappings, and aliases that you specify inside the index template are applied last.
PUT _index_template/daily_logs
{
"index_patterns": [
"logs-2020-01-*"
],
"template": {
"aliases": {
"my_logs": {}
},
"settings": {
"number_of_shards": 2,
"number_of_replicas": 1
},
"mappings": {
"properties": {
"timestamp": {
"type": "date",
"format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"
},
"value": {
"type": "double"
}
}
}
},
"priority": 200,
"composed_of": [
"component_template_1",
"component_template_2"
],
"version": 3,
"_meta": {
"description": "using component templates"
}
}
If you create an index named logs-2020-01-01
, you can see that it derives its mappings and settings from both the component templates:
PUT logs-2020-01-01
GET logs-2020-01-01
{
"logs-2020-01-01": {
"aliases": {
"my_logs": {}
},
"mappings": {
"properties": {
"@timestamp": {
"type": "date"
},
"ip_address": {
"type": "ip"
},
"timestamp": {
"type": "date",
"format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"
},
"value": {
"type": "double"
}
}
},
"settings": {
"index": {
"creation_date": "1625382479459",
"number_of_shards": "2",
"number_of_replicas": "1",
"uuid": "rYUlpOXDSUSuZifQLPfa5A",
"version": {
"created": "7100299"
},
"provided_name": "logs-2020-01-01"
}
}
}
}
You can specify the following template options:
Option | Type | Description | Required |
---|---|---|---|
template |
Object |
Specify index settings, mappings, and aliases. | No |
priority |
Integer |
The priority of the index template. | No |
composed_of |
String array |
The names of component templates applied on a new index together with the current template. | No |
version |
Integer |
Specify a version number to simplify template management. Default is null . |
No |
_meta |
Object |
Specify meta information about the template. | No |