[DOC] Add new documentation for date index name processor (#5398)

* Add new processor documentation

Signed-off-by: Melissa Vagi <vagimeli@amazon.com>
---------

Signed-off-by: Melissa Vagi <vagimeli@amazon.com>
Co-authored-by: Heemin Kim <heemin@amazon.com>
Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

_ingest-pipelines/processors/date-index-name.md

@@ -0,0 +1,154 @@
+---
+layout: default
+title: Date index name
+parent: Ingest processors
+nav_order: 55
+---
+
+# Date index name
+
+The `date_index_name` processor is used to point documents to the correct time-based index based on the date or timestamp field within the document. The processor sets the `_index` metadata field to a [date math]({{site.url}}{{site.baseurl}}/field-types/supported-field-types/date/#date-math) index name expression. Then the processor fetches the date or timestamp from the `field` field in the document being processed and formats it into a date math index name expression. The extracted date, `index_name_prefix` value, and `date_rounding` value are then combined to create the date math index expression. For example, if the `field` field contains the value `2023-10-30T12:43:29.000Z` and `index_name_prefix` is set to `week_index-` and `date_rounding` is set to `w`, then the date math index name expression is `week_index-2023-10-30`. You can use the `date_formats` field to specify how the date in the date math index expression should be formatted.
+
+The following is the syntax for the `date_index_name` processor:
+
+```json
+{
+  "date_index_name": {
+    "field": "your_date_field or your_timestamp_field",
+    "date_rounding": "rounding_value"
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Configuration parameters
+
+The following table lists the required and optional parameters for the `date_index_name` processor.
+
+Parameter | Required/Optional | Description |
+|-----------|-----------|-----------|
+`field`  | Required  | The date or timestamp field in the incoming document. Supports [template snippets]({{site.url}}{{site.baseurl}}/ingest-pipelines/create-ingest/#template-snippets). |
+`date_rounding`  | Required | The rounded date format within the index name . Valid values are `y` (year), `M` (month), `w` (week), `d` (day), `h` (hour), `m` (minute), and `s` (second). |
+`date_formats` | Optional | An array of date formats used to parse the date or timestamp field. Valid options include a java time pattern or one of the following formats: ISO8601, UNIX, UNIX_MS, or TAI64N. Default is `yyyy-MM-dd'T'HH:mm:ss.SSSXX`. |
+`index_name_format` | Optional | The date format. Default is `yyyy-MM-dd`. Supports [template snippets]({{site.url}}{{site.baseurl}}/ingest-pipelines/create-ingest/#template-snippets). |
+`index_name_prefix` | Optional | The index name prefix to append before the date. Supports [template snippets]({{site.url}}{{site.baseurl}}/ingest-pipelines/create-ingest/#template-snippets).
+`description`  | Optional  | A brief description of the processor.  |
+`if` | Optional | A condition for running this processor. |
+`ignore_failure` | Optional | If set to `true`, failures are ignored. Default is `false`. |
+`locale` | `locale`  | Optional  | The locale to use when parsing the month name and week day of the date. Default is `ENGLISH`. Supports [template snippets]({{site.url}}{{site.baseurl}}/ingest-pipelines/create-ingest/#template-snippets).  |
+`on_failure` | Optional | A list of processors to run if the processor fails. |
+`tag` | Optional | An identifier tag for the processor. Useful for debugging to distinguish between processors of the same type. |
+`timezone`  | Optional  | The time zone to use when parsing the date. Default is `UTC`. |
+
+## Using the processor
+
+Follow these steps to use the processor in a pipeline.
+
+**Step 1: Create a pipeline.**
+
+The following query creates a pipeline, named `date-index-name1`, that uses the `date_index_name` processor to index logs into monthly indexes: 
+
+```json
+PUT /_ingest/pipeline/date-index-name1
+{
+  "description": "Create weekly index pipeline",
+  "processors": [
+    {
+      "date_index_name": {
+        "field": "date_field",
+        "index_name_prefix": "week_index-",
+        "date_rounding": "w",
+        "date_formats": ["YYYY-MM-DD"]
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+**Step 2 (Optional): Test the pipeline.**
+
+It is recommended that you test your pipeline before you ingest documents.
+{: .tip}
+
+To test the pipeline, run the following query:
+
+```json
+POST _ingest/pipeline/date-index-name1/_simulate
+{
+  "docs": [
+    {
+      "_index": "testindex1",
+      "_id": "1",
+      "_source": {
+        "date_field": "2023-10-30"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The following example response confirms that the pipeline is working as expected:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "<week_index-{2023-10-01||/w{yyyy-MM-dd|UTC}}>",
+        "_id": "1",
+        "_source": {
+          "date_field": "2023-10-30"
+        },
+        "_ingest": {
+          "timestamp": "2023-11-13T18:23:10.408593092Z"
+        }
+      }
+    }
+  ]
+}
+```
+
+**Step 3: Ingest a document.**
+
+The following query ingests a document into an index named `testindex1`:
+
+```json
+PUT testindex1/_doc/1?pipeline=date-index-name1
+{
+  "date_field": "2023-10-30"
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The request indexes the document into the index `week_index-2023-10-23` and will index all documents with a timestamp within that week into the same index because the pipeline rounds by week.
+
+```json
+{
+  "_index": "week_index-2023-10-30",
+  "_id": "1",
+  "_version": 4,
+  "result": "updated",
+  "_shards": {
+    "total": 2,
+    "successful": 1,
+    "failed": 0
+  },
+  "_seq_no": 3,
+  "_primary_term": 1
+}
+```
+
+**Step 4 (Optional): Retrieve the document.**
+
+To retrieve the document, run the following query:
+
+```json
+GET week_index-2023-10-30/_doc/1
+```
+{% include copy-curl.html %}