Added Index Template Guide

Signed-off-by: Theo Truong <[email protected]>

guides/index_lifecycle.md

@@ -133,7 +133,7 @@ We can also delete multiple indices at once:
 ```ruby
 client.indices.delete(index: [:movies, :paintings, :burner], ignore: 404)
 ```
-Notice that we are passing `ignore: 404` to the request. This tells the client to ignore the `404` error if the index doesn't exist for deletion. Without it, the above `delete` request will throw an error because the `movies` index have already been deleted in the previous example.
+Notice that we are passing `ignore: 404` to the request. This tells the client to ignore the `404` error if the index doesn't exist for deletion. Without it, the above `delete` request will throw an error because the `movies` index has already been deleted in the previous example.
 
 ## Cleanup
 

guides/index_template.md

@@ -0,0 +1,182 @@
+# Index Template
+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.
+
+## Setup
+
+Assuming you have OpenSearch running locally on port 9200, you can create a client instance
+with the following code:
+```ruby
+require 'opensearch-ruby'
+client = OpenSearch::Client.new({ host: 'localhost' })
+```
+
+## Index Template API Actions
+
+### Create an Index Template
+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:
+
+```ruby
+client.indices.put_index_template(
+  name: :books,
+  body: {
+    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' }
+        }
+      }
+    }
+  }
+)
+```
+
+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:
+
+```ruby
+client.indices.create(index: 'books-nonfiction')
+puts client.indices.get(index: 'books-nonfiction')
+```
+
+### Multiple Index Templates
+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:
+
+```ruby
+client.indices.put_index_template(
+  name: 'books',
+  body: {
+    index_patterns: ['books-*'],
+    priority: 0, # default priority
+    template: {
+      settings: {
+        index: {
+          number_of_shards: 3,
+          number_of_replicas: 0
+        }
+      }
+    }
+  }
+)
+
+client.indices.put_index_template(
+  name: 'books-fiction',
+  body: {
+    index_patterns: ['books-fiction-*'],
+    priority: 1, # higher priority than the `books` template
+    template: {
+      settings: {
+        index: {
+          number_of_shards: 1,
+          number_of_replicas: 1
+        }
+      }
+    }
+  }
+)
+```
+
+When we create an index named `books-fiction-romance`, OpenSearch will apply the `books-fiction-*` template's settings to the index:
+
+```ruby
+client.indices.create(index: 'books-fiction-romance')
+puts client.indices.get(index: 'books-fiction-romance')
+```
+
+### Composable Index Templates
+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:
+
+```ruby
+client.cluster.put_component_template(
+  name: 'books_mappings',
+  body: {
+    template: {
+      mappings: {
+        properties: {
+          title: { type: 'text' },
+          author: { type: 'text' },
+          published_on: { type: 'date' },
+          pages: { type: 'integer' }
+        }
+      }
+    }
+  }
+)
+
+client.indices.put_index_template(
+  name: 'books',
+  body: {
+    index_patterns: ['books-*'],
+    composed_of: ['books_mappings'], # use the `books_mappings` component template
+    priority: 0,
+    template: {
+      settings: {
+        index: {
+          number_of_shards: 3,
+          number_of_replicas: 0
+        }
+      }
+    }
+  }
+)
+
+client.indices.put_index_template(
+  name: 'books',
+  body: {
+    index_patterns: ['books-*'],
+    composed_of: ['books_mappings'], # use the `books_mappings` component template
+    priority: 1,
+    template: {
+      settings: {
+        index: {
+          number_of_shards: 1,
+          number_of_replicas: 1
+        }
+      }
+    }
+  }
+)
+``` 
+
+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:
+
+```ruby
+client.indices.create(index: 'books-fiction-horror')
+puts client.indices.get(index: 'books-fiction-horror')
+```
+
+### Get an Index Template
+You can get an index template with the `get_index_template` API action:
+
+```ruby
+puts client.indices.get_index_template(name: 'books')
+```
+
+### Delete an Index Template
+You can delete an index template with the `delete_template` API action:
+
+```ruby
+client.indices.delete_index_template(name: 'books')
+```
+
+## Cleanup
+Let's delete all resources created in this guide:
+
+```ruby
+client.indices.delete(index: 'books-*')
+client.indices.delete_index_template(name: 'books-fiction')
+client.cluster.delete_component_template(name: 'books_mappings')
+```
+
+
+
+