207 lines
4.6 KiB
Markdown
207 lines
4.6 KiB
Markdown
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---
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layout: default
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title: Index Templates
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parent: OpenSearch
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nav_order: 5
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---
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# Index template
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Index templates let you initialize new indices with predefined mappings and settings. For example, if you continuously index log data, you can define an index template so that all of these indices have the same number of shards and replicas.
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OpenSearch switched from `_template` to `_index_template` in version 7.8. Use `_template` for older versions of OpenSearch.
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{: .note }
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---
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#### Table of contents
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1. TOC
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{:toc}
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---
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## Create template
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To create an index template, use a POST request:
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```json
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POST _index_template
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```
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This command creates a template named `daily_logs` and applies it to any new index whose name matches the regular expression `logs-2020-01-*` and also adds it to the `my_logs` alias:
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```json
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PUT _index_template/daily_logs
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{
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"index_patterns": [
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"logs-2020-01-*"
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],
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"template": {
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"aliases": {
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"my_logs": {}
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},
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"settings": {
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"number_of_shards": 2,
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"number_of_replicas": 1
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},
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"mappings": {
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"properties": {
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"timestamp": {
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"type": "date",
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"format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"
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},
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"value": {
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"type": "double"
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}
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}
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}
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}
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}
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```
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You should see the following response:
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```json
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{
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"acknowledged": true
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}
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```
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If you create an index named `logs-2020-01-01`, you can see that it has the mappings and settings from the template:
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```json
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PUT logs-2020-01-01
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GET logs-2020-01-01
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```
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```json
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{
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"logs-2020-01-01": {
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"aliases": {
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"my_logs": {}
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},
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"mappings": {
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"properties": {
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"timestamp": {
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"type": "date",
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"format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"
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},
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"value": {
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"type": "double"
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}
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}
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},
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"settings": {
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"index": {
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"creation_date": "1578107970779",
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"number_of_shards": "2",
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"number_of_replicas": "1",
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"uuid": "U1vMDMOHSAuS2IzPcPHpOA",
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"version": {
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"created": "7010199"
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},
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"provided_name": "logs-2020-01-01"
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}
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}
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}
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}
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```
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Any additional indices that match this pattern---`logs-2020-01-02`, `logs-2020-01-03`, and so on---will inherit the same mappings and settings.
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## Retrieve template
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To list all index templates:
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```json
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GET _cat/templates
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```
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To find a template by its name:
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```json
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GET _index_template/daily_logs
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```
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To get a list of all your templates:
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```json
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GET _index_template/daily_logs
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```
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To get a list of all templates that match a pattern:
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```json
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GET _index_template/daily*
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```
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To check if a specific template exists:
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```json
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HEAD _index_template/<name>
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```
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## Configure multiple templates
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You can create multiple index templates for your indices. If the index name matches more than one template, OpenSearch merges all mappings and settings from all matching templates and applies them to the index.
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The settings from the more recently created index templates override the settings of older index templates. So, you can first define a few common settings in a generic template that can act as a catch-all and then add more specialized settings as required.
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An even better approach is to explicitly specify template priority using the `order` parameter. OpenSearch applies templates with lower priority numbers first and then overrides them with templates that have higher priority numbers.
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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:
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#### Template 1
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```json
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PUT _index_template/template-01
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{
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"index_patterns": [
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"logs*"
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],
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"priority": 0,
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"template": {
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"settings": {
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"number_of_shards": 2
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}
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}
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}
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```
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#### Template 2
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```json
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PUT _index_template/template-02
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{
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"index_patterns": [
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"logs-2020-01-*"
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],
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"priority": 1,
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"template": {
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"settings": {
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"number_of_shards": 3
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}
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}
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}
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```
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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.
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## Delete template
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You can delete an index template using its name, as shown in the following command:
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```json
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DELETE _index_template/daily_logs
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```
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## Index template options
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You can specify the options shown in the following table:
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Option | Type | Description | Required
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:--- | :--- | :--- | :---
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`priority` | `Number` | Specify the priority of the index template. | No
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`create` | `Boolean` | Specify whether this index template should replace an existing one. | No
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