[Backport 2.14] [DOC] Add script processor documentation

_ingest-pipelines/processors/script.md

@@ -0,0 +1,155 @@
+---
+layout: default
+title: script
+parent: Ingest processors
+nav_order: 230
+---
+
+# Script processor
+
+The `script` processor executes inline and stored scripts that can modify or transform data in an OpenSearch document during the ingestion process. The processor uses script caching for improved performance because scripts may be recompiled per document. Refer to [Script APIs](https://opensearch.org/docs/latest/api-reference/script-apis/index/) for information about working with scripts in OpenSearch. 
+
+The following is the syntax for the `script` processor:
+
+```json
+{
+  "processor": {
+    "script": {
+      "source": "<script_source>",
+      "lang": "<script_language>",
+      "params": {
+        "<param_name>": "<param_value>"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Configuration parameters
+
+The following table lists the required and optional parameters for the `script` processor.
+
+| Parameter  | Required/Optional  | Description  |
+|---|---|---|
+`source`  | Optional  | The Painless script to be executed. Either `id` or `source` must be specified---but not both. If `source` is specified, then the script is executed using the provided source code.
+`id` | Optional | The ID of a stored script previously created using the [Create Stored Script API]({{site.url}}{{site.baseurl}}/api-reference/script-apis/create-stored-script/). Either `id` or `source` must be specified, but not both. If `id` is specified, then the script source is retrieved from the stored script with the specified ID. 
+`lang`  | Optional  | The programming language of the script. Default is `painless`.
+`params` | Optional |  The parameters that can be passed to the script.
+`description`  | Optional  | A description of the processor's purpose or configuration.
+`if` | Optional | Specifies to conditionally execute the processor.
+`ignore_failure` | Optional | Specifies to ignore processor failures. See [Handling pipeline failures]({{site.url}}{{site.baseurl}}/ingest-pipelines/pipeline-failures/).
+`on_failure` | Optional | Specifies a list of processors to run if the processor fails during execution. These processors are executed in the order they are specified. See [Handling pipeline failures]({{site.url}}{{site.baseurl}}/ingest-pipelines/pipeline-failures/).
+`tag` | Optional | An identifier tag for the processor. Useful for debugging in order to distinguish between processors of the same type.
+
+## 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 `my-script-pipeline` that uses the `script` processor to convert the `message` field to uppercase: 
+
+```json
+PUT _ingest/pipeline/my-script-pipeline
+{
+  "description": "Example pipeline using the ScriptProcessor",
+  "processors": [
+    {
+      "script": {
+        "source": "ctx.message = ctx.message.toUpperCase()",
+        "lang": "painless",
+        "description": "Convert message field to uppercase"
+      }
+    }
+  ]
+}
+```
+{% 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/my-script-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_source": {
+        "message": "hello, world!"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The following example response confirms that the pipeline is working as expected:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "_index",
+        "_id": "_id",
+        "_source": {
+          "message": "HELLO, WORLD!"
+        },
+        "_ingest": {
+          "timestamp": "2024-05-30T16:24:23.30265405Z"
+        }
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+### Step 3: Ingest a document 
+
+The following query ingests a document into an index named `testindex1`:
+
+```json
+POST testindex1/_doc?pipeline=my-script-pipeline
+{
+  "message": "hello, world!"
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The response confirms that the document has been indexed into `testindex1` and has indexed all documents with the `message` field converted to uppercase:
+
+```json
+{
+  "_index": "testindex1",
+  "_id": "1",
+  "_version": 1,
+  "result": "created",
+  "_shards": {
+    "total": 2,
+    "successful": 1,
+    "failed": 0
+  },
+  "_seq_no": 6,
+  "_primary_term": 2
+}
+```
+{% include copy-curl.html %}
+
+### Step 4 (Optional): Retrieve the document
+
+To retrieve the document, run the following query:
+
+```json
+GET testindex1/_doc/1
+```
+{% include copy-curl.html %}