Index templates are a convenient way to define settings, mappings, and aliases for one or more indices when they are created. In this guide, you'll learn how to create an index template and apply it to an index.
Assuming you have OpenSearch running locally on port 9200, you can create a client instance with the following code:
package main
import (
"github.com/opensearch-project/opensearch-go/v2"
"log"
)
func main() {
client, err := opensearch.NewDefaultClient()
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", client)
}
You can create an index template to define default settings and mappings for indices of certain patterns. The following example creates an index template named books
with default settings and mappings for indices of the books-*
pattern:
body := strings.NewReader(`{
"index_patterns": ["books-*"],
"template": {
"settings": {
"index": {
"number_of_shards": 3,
"number_of_replicas": 0
}
},
"mappings": {
"properties": {
"title": { "type": "text" },
"author": { "type": "text" },
"published_on": { "type": "date" },
"pages": { "type": "integer" }
}
}
}
}`)
res, err := client.Indices.PutIndexTemplate("books", body)
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
Now, when you create an index that matches the books-*
pattern, OpenSearch will automatically apply the template's settings and mappings to the index. Let's create an index named books-nonfiction
and verify that its settings and mappings match those of the template:
res, err = client.Indices.Create("books-nonfiction")
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
// check mappings properties
res, err = client.Indices.Get([]string{"books-nonfiction"})
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
If multiple index templates match the index's name, OpenSearch will apply the template with the highest priority. The following example creates two index templates named books-*
and books-fiction-*
with different settings:
res, err := client.Indices.PutIndexTemplate("books", strings.NewReader(`{
"index_patterns": ["books-*"],
"priority": 0,
"template": {
"settings": {
"index": {
"number_of_shards": 3,
"number_of_replicas": 0
}
}
}
}`))
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
// higher priority than the `books` template
res, err = client.Indices.PutIndexTemplate("books-fiction", strings.NewReader(`{
"index_patterns": ["books-fiction-*"],
"priority": 1,
"template": {
"settings": {
"index": {
"number_of_shards": 1,
"number_of_replicas": 1
}
}
}
}`))
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
When we create an index named books-fiction-romance
, OpenSearch will apply the books-fiction-*
template's settings to the index:
res, err = client.Indices.Create("books-fiction-romance")
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
res, err = client.Indices.Get([]string{"books-fiction-romance"})
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
Composable index templates are a new type of index template that allow you to define multiple component templates and compose them into a final template. The following example creates a component template named books_mappings
with default mappings for indices of the books-*
and books-fiction-*
patterns:
// delete index templates if they exist
res, err := client.Indices.DeleteIndexTemplate("books-*")
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
// delete indices if they exist
res, err = client.Indices.Delete([]string{"books-*", "books-fiction-*"})
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
// Composable Index Templates
res, err = client.Cluster.PutComponentTemplate("books_mappings", strings.NewReader(`{
"template": {
"mappings": {
"properties": {
"title": { "type": "text" },
"author": { "type": "text" },
"published_on": { "type": "date" },
"pages": { "type": "integer" }
}
}
}
}`))
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
// use the `books_mappings` component template with priority 0
res, err = client.Indices.PutIndexTemplate("books", strings.NewReader(`{
"index_patterns": ["books-*"],
"composed_of": ["books_mappings"],
"priority": 0,
"template": {
"settings": {
"index": {
"number_of_shards": 3,
"number_of_replicas": 0
}
}
}
}`))
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
// use the `books_mappings` component template with priority 1
res, err = client.Indices.PutIndexTemplate("books", strings.NewReader(`{
"index_patterns": ["books-fiction-*"],
"composed_of": ["books_mappings"],
"priority": 1,
"template": {
"settings": {
"index": {
"number_of_shards": 3,
"number_of_replicas": 0
}
}
}
}`))
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
When we create an index named books-fiction-horror
, OpenSearch will apply the books-fiction-*
template's settings, and books_mappings
template mappings to the index:
res, err = client.Indices.Create("books-fiction-horror")
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
res, err = client.Indices.Get([]string{"books-fiction-horror"})
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
You can get an index template with the get_index_template
API action:
res, err = client.Indices.GetIndexTemplate(
client.Indices.GetIndexTemplate.WithName("books"),
)
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
You can delete an index template with the delete_template
API action:
res, err = client.Indices.DeleteIndexTemplate("books")
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)
Let's delete all resources created in this guide:
res, err = client.Indices.DeleteIndexTemplate("books-fiction")
if err != nil {
log.Printf("error occurred: [%s]", err.Error())
}
log.Printf("response: [%+v]", res)